cha1~~~--tij ~ommittee
TRANSCRIPT
THE REDUCTIVE COUPLING OF AROMATIC
POLYNUCLEAR NITRO COMPOUNDS
by
MEILING TSAI~ B.S.
A THESIS
IN
CHEMISTRY
Submitted to t he Graduate Faculty of Texas Technological College
in Partial Fulfillment of the Requirements for
the ·Degree of
MASTER OF SCIENCE
Approved
Cha1~~~- -tiJ the ~ommittee
" IS .. --..... I
Aecepted
Dean of the Gt-aduate School
T3
no '*3 coy. ^ ACKNOWLEDGMENT
I am deeply Indebted to Dr. H. J« Shine for his sug
gestion of the problem investigated herein^ and for his
valuable advice and criticism which he has extended on all
phases of the work. My thanks go also to other members of
the Chemistry Department for the aid^ advice and encourage
ment which they have been kind enough to give.
ii
TABLE OF CONTENTS Page
LIST OF TABLES vli
LIST OF FIGURES viii
CHAPTER
I. INTRODUCTION 1
II. REVIEW OF THE LITERATURE 3
Reductive Coupling of 1-Nltronaphthalene. . 3
Reductive Coupling of Nitro Compounds with Metal Hydride Complexes 7
Reduction with Lithi\am Aluminum
Hydride 7
Reduction with Sodium Borohydrlde . . 9
PotassiiATO Borohydrlde 10
Reduction with Lithium Borohydrlde . . 11
Reduction with Sodium Trimethoxyborohydride 11
Reduction with Sodium Triethoxyaluminvimhydride . . . • , 12
Reductive Coupling of Nitro Compounds
Miscellaneous Methods . . . . * • . • 13
Reduction with Diborane 13
Coupling of Organometallies by
Nitrous Oxide l4
Hydrogenolysis of Nitro Group 15
III. EXPERIMENTAL l8
Reduction with Lithium Aluminum Hydride. . 18
Preparation and Analysis of Lithium
Aluminum Hydride Solution . . . . 18
Reduction with Lithium Alumin\am Hydride 20
ill
iv
Direct addition method 20
Extraction method 20
Inverse addition method 20
Reduction of Nitrobenzene 21
NB-LAH-I 21
NB-LAH-II 22
NB-LAII-III 22
Reduction of 1-Nltr©naphthalene 23
NN-LAH-I 23
NN-LAH-II 24
NN-LAH-III 25
NN-LAH-IV 26
NN-LAH-V 26
NN-LAH-VI 27
NN-LAH-VII (Inverse addition) 29
Reduction of 5-Bromo-l-nitronaphthalene. . 33
Reduction of l,l*-Azonaphthalene 34
AN-LAH-I 34
AN-LAH-II 34
Reduction with Sodium Borohydrlde 35
Materials 35
Standardization of Sodium Borohydrlde
Solution 35
Reduction of l-Nltr©naphthalene 36
NN-NBH-I 36
NN-NBH-II 38 NN-NBH-III 39
V
Reduction of p-Dlnitrobenzene 4l
Attempted Hydrogenolysis of
1-Naphthylamlne 42
Reduction with Potassium Borohydrlde . . . 43
Determination of Purity of Potassium
Borohydrlde 43
Reduction of Nitrobenzene 43
Reduction of l-Nltr©naphthalene . . . . 44
NN-KBH-I 44
NN-KBH-II 45
NN-KBH-III 46
NN-KBH-IV 47
Reduction of p-Dlnitrobenzene 48
DNB-KBH-I 48
DNB-KBH-II 50
Reductl©n with Lithium Borohydrlde . . . . 52
NN-LBH-I 52
NN-LBH-II 53
NN-LBH-III 54
Reduction with Diborane 56
NN-DB-I 56
NN-DB-II 57
Preparation of Naphthyl Lithl\im and Its Reaction with Nitrous Oxide 57
NL-NO-I 57
NL-NO-II 58
Infra-Red Absorptl©n Spectrum ©f the C©mp©und (A), DNB-KBH-I 59
vi
Discussion of Results 62
IV. CONCLUSIONS 67
REFERENCES CITED 53
LIST OF TABLES
TABLE Page
I. The Reduction of 1-Nltronaphthalene with Lithium Aluminum Hydride 32
II. The Reducti©n of l-Nltronaphthalene with S©di\im B©r©hydride 4l
III. The Reducti©n ©f l-Nltronaphthalene with P©tassium Bor©hydride 48
IV. Infra-Red Spectrum ©f the C©mp©und (A), DNB-KBH-I 60
vli
LIST OF FIGURES
FIGURE Page
1. Infra-Red Spectrum ©f the C©mp©\ind ( A ) , DNB-KBH-I 61
v i i i
CHAPTER I
INTRODUCTION
It is generally considered as a comm©n pr©perty ©f
ar©matic nitr© c©mpounds that they are tr£Lnsf©rmed Int© az©xy-,
azo-, or hydrazo c©mp©unds by the actl©n of mild reducing
agents in an alkaline medium, such as sodium methoxide in
methanol, zinc and alcoh©lic potash, arsenous ©xide in aque-
©us s©dium hydroxide or zinc dust and alcoh©lic ammonia (l).
Although azoxy- and az©benzene have been prepared in high
yield by the actl©n ©f these reagents, ©nly a few meth©ds can
be applied t© the preparati©n of azoxy- or azonaphthalenes
directly fr©m nitr©naphthalenes (2),
During the past decade a c©nsiderable am©unt of re
search has been directed toward the reduction of organic com
pounds with metal hydride complexes. Among such reductions,
Br©wn and Nystr©m (3) have reported the reductive coupling
of nitrobenzene with lithium aluminum hydride to form azo-
benzene. In the research work to be described. Investigation
of the actions of metal hydride complexes and other related
reducing agents on l-nltr©naphthalene was undertaken with the
hope of causing coupling to l,l'-azonaphthalene.
The results rep©rted in this thesis sh©w the vast dif
ference in the behavi©r ©f 1-nitronaphthalene from that of
nitrobenzene; further the results indicate that hydr©gen©ly-
tic cleavage ©f nitro group of 1-nltronaphthalene takes place
during the course ©f reductl©n. The results will als© sh©w
that nucle©philic replacement ©f nitr© gr©up takes place in
the benzene series in certain circumstances. The experimen
tal work described in this thesis shows how the products ©f
the reduction were isolated and identified.
CHAPTER II
REVIEW OF THE LITERATURE
Reductive Coupling ©f 1-Nitr©naphthalene
D©er (4) and Kl©buk©wski (5) had claimed t© ©btaln
az©naphthalene by the destructive dlstillati©n ©f nltr©-
naphthalene over zinc dust or lime. Their azonaphthalene,
the lem©n-yell©w substance ©f the c©mp©siti©n 02(flil^^2' ^^^^'
ing p©lnt 280°, was, h©wever, identified as l,2:5,6-dlben-
z©phenazlne by Witt (6), Therefore Wacker (7) was the first
one t© obtain azonaphthalene or the related azoxy- and hydra-
zonaphthalene, directly fr©m reductive coupling of nltr©-
naphthalene. Fr©m the mixture ©f l-nltr©naphthalene with
aram©nium chl©ride and zinc dust in aque©us alc©h©l system,
Wacker ©btained mainly l-naphthylhydr©xylamine and small
am©unt ©f l,l'-az©xynaphthalene. He explained the f©rmatl©n
©f l,l'-az©xynaphthalene as the dlspr©p©rtl©natl©n ©f 1-
naphthylhydr©xylamine f©rmed fr©m the acti©n ©f reducing
agent ©n l-nitr©naphthalene.
NHOH
T© pr©ve this c©urse he succeeded in ©btainlng l,l*-azoxy-
naphthalene in 28-305 yield by merely heating 1-naphthyl-
hydr©xylamine is©lated fr©m the reducti©n pr©ducts. H©wever
he did n©t menti©n the ls©lation ©f 1-naphthylamlne which,
as indicated, is also f©rmed in the disproportionati©n.
The c©urse of reductive coupling of nitro compounds
is now generally believed as the reaction between nitros©
and hydroxylamin© c©mp©unds which are the first and sec©nd
reducti©n products to be formed.
2H NO NHOH
^ ^ 2H r r ^
" ^ ^ ^ " ^ ^
-H 0
O-r^ 2H
(y-^ 2H
Q K N H - N . ^
By the electrolytic reduction with potential and current
density properly adjusted, the product ©f each stage can be
identified (l).
Whereas ©nly little az©xynaphthalene was ©btained fr©m
the neutral reductl©n, absolutely no azoxynaphthalene was ©b-
tainable from an alkaline medium, which, on the ©ther hand,
had been sh©wn t© be essential for the preparation of az©xy-
or azobenzene (l). Yet s©me substituted 1-naphthalenes
yielded az©xynaphthalene derivatives fr©m b©th neutral and
alkaline medium; ©ccasi©nally in almost quantitative yield.
Wacker thus obtained 5,5'-dinitroaz©xynaphthalene with zinc
dust and ammonium chloride in alcoh©l, and phenylhydrazine
and s©dium hydr©xide in alc©h©l; l,8-dinitr©naphthalene gave
the same result, l,l»az©xynaphthalene-5,5*-disulf©nlc acid
was ©btained in 65^ yield fr©m s©dium l-nitr©naphthalene-5-
sulfonate with gluc©se ©r phenylhydrazine ajid sodium hydrox
ide in alcohol (8).
In contrast with nitrobenzene, which gave 23.65 of
ethylaniline and 29,7^ of azobenzene when treated with ethyl
magnesium iodide, 1-nitronaphthalene gave 32^ of ethyl
1-naphthylamine and 7.1^ of 1,1»-azonaphthalene with the
same reducing agent (9).
An extensive investigation ©f the reductive c©upling
©f 1-nitronaphthalene was undertaken by Cumming and Steel
(lO). Sodium-amalgam, and sodium hydroxide and zinc in al
coholic s©luti©n failed t© give any satisfact©ry result. By
varying the am©unt of sodium hydroxide and the type ©f s©l-
vent, it was c©ncluded that the presence of sodium hydroxide
appeared to hinder the reduction t© az©xynaphthalene and
tended t© pr©duce tar and naphthylamine. With zinc and am-
m©nium chloride in aqueous-ale©hoi solution, the reductive
coupling to©k place at 70°. Bel©w 70° naphthylhydr©xylamine
was f©rmed, while at higher temperature, that is, ab©ve 75°>
naphthylamine was the main pr©duct. Az©xy-, az©-, and hydra-
z©naphthalene were obtained consecutively by varying the
am©unt ©f zinc added. H©wever, the validity ©f this neutral
reducti©n method is questionable, because a melting point of
274° was given for l,l»-hydrazonaphthalene (true melting
p©int 153 ) and n© percentage yield was given f©r the products
obtained.
Although an alkaline mediiam was demonstrated to be un
satisfactory for the chemical reductive coupling of 1-nitro
naphthalene, in the case of the electrolytic reductl©n ©f
nitr©naphthalene the yield ©f hydraz©naphthalene increased
with increasing pH ©f the catholyte. C©ncentrated solutions
of the mixtures of sodium and potassium xylene sulfonate auid
also of xylenesulfonic acid were fo\md to be excellent sol
vents for nitro compounds. The yield of hydrazonaphthalene
was, however, undetermined (11).
The chemical method of the reductive coupling of nitro-
naphthalene has been shown, with few excepti©ns, as unsatis-
fact©ry. Therefore the Sandmeyer reaction has served ex
clusively as the source of azonaphthalenes. A modified
method gives 1,1'-azonaphthalene in 80^ yield and 2,2'-
azonaphthalene in 90$ yield by increasing the rate of addi
tion of the diazoni"um s©luti©n t© the c©upllng medium c©n-
sisting of copper sulfate and hydr©xylamine in aque©us am-
moTXia (12).
Reductive Coupling ©f Nitr© Compounds
with Metal Hydride C©mplexes
Reducti©n with Lithium Aluminum Hydride
Lithium aluminum hydride is a micr©crystalllne s©lid
which is stable in dry air at r©©m temperature. It has been
p©stulated t© exist as a complex salt Li+ /!SlHi 7 The aluml-
n\m hydride ion, ^KlY^T/", in ether solution has a tetrahedral
structure.
Lithivim aluminum hydride may be heated without appre
ciable dec©mp©siti©n t© temperatures bel©w 100° in vacu©.
At 150°, dec©mp©slti©n results in the ev©lutl©n ©f hydr©gen
and f©rmati©n ©f lithium hydride and aluminum. The vig©r©us
reaction of lithium aluminiAra hydride with water liberates
hydrogen. Lithium aliJminum hydride is soluble in c©mp©unds
©f the ether class. The ethereal s©luti©ns are miscible with
s©me hydr©carbons, permitting reacti©n t© be carried ©ut in
which the reactants are ether inscluble but hydr©carb©n
s©luble.
The reducti©n ©f ar©matic nitr© c©mp©unds with lithium
aluminum hydride usually yields az© derivatives acc©rding to
8
the overall equation (I3)
NO,
+ 2LiAIH, ^ \ /-f^^N-^ ^-H2LiAI02+4H,
With nitrobenzene in anhydrous ether and addition of lithium
aluminum hydride soluti©n in the same s©lvent at -78 and
subsequent reacti©n at r©©m temperature, Br©wn and Nystr©m
(3) have ©btained az©benzene in 855 yield.
Although Kvajisnlcka indicated that the nitr© gr©up in
m-nitr©benzaldehyde was unattacked by lithium aluminum hy
dride (l3)i the ©pp©site has been ©bserved by Gayl©rd ajid
Snyder (l4). The latter ©btained m,m*-az©benzyl alc©h©l fr©m
m-nitr©benzaldehyde. The yield, h©wever, was 28.55 > very much
l©wer than the 85$ yield ©f azobenzene from nitrobenzene.
CHO
Li All^
k^NO^
HgOH
N = ^
CH-OH
Although lithium aluminum hydride reduction ©f nitr©-
benzene involves the participation of two molecules, f©rma-
tion of the az© gr©up fr©m 2,2'-dinitrodiphenyl is intra-
m©lecular (1, 15).
NO^ 0^ N==N
/
n Ried and Muller (l6) reported that the reduction of
4,4»-dinitroaz©benzene with lithium aluminum hydride in a
tetrahydr©furan-ether mixture yielded 555 ©f 4,4'-diamin©-
az©benzene with n© evidence ©f p©lyaz© c©mp©unds. Wlbert and
Jahn have sh©wn that the lithium aluminum hydride reducti©n
©f p-nitr©toluene yields 65^ ©f p-az©t©luene and 10$ ©f p-
toluidine (17). These are the ©nly tw© cases ©f the f©rma-
ti©n of amines in the lithium aluminum hydride reduction of
aromatic nitro c©mp©unds in the benzene series. There has
been n© report on the aromatic nitro comp©unds ©f series
other than benzene.
Reduction with Sodium B©rohydride
Sodlvim b©r©hydride is a white crystalline, salt-like
s©lid ©f remarkable stability. The s©lid b©r©hydride is
stable in dry air t© 300°. N© apparent change ©ccurs in
vacuo at temperatures approaching 400°. The decomp©siti©n
bec©mes rapid ab©ve 550 giving principally hydr©gen and a
trace ©f diborane. The solid bor©hydride Ignites t© a free
flame in air and burns quietly (I8). S©dium b©rohydride
dissolves in cold water without extensive ev©lutl©n ©f hy-
dr©gen, and no appreciable reaction with water at r©©m tem
perature occurs above pH 11.5. The bor©hydride is n©t ap
preciably soluble in ethers. It is very soluble in liquid
ammonia and in the lower aliphatic amines. The best sol
vents recommended are diglyme (diethylene glycol dimethyl
10
ether) and triglyme (triethylene glycol dimethyl ether) (19).
Chalkin aind Brown (20) reported in their investigation
of reductions with sodium bor©hydride that the nitr© gr©up
was resistant t© attack. This was c©nfirmed by several ©ther
w©rkers. However, Weil and Panson rep©rted that nitrobenzene,
when refluxed with sodium b©r©hydride in the presence ©f
s©dium hydr©xide at temperature between 90° and 100 in diglyme,
yielded 585 ©f az©xybenzene (21).
P©tassi\am B©r©hydride
P©tassium b©r©hydride is a white crystalline material
which is n©n-hygr©sc©pic and stable in mclst and dry air.
Decompositi©n without melting occurs at about 500° in vacuo
without evoluti©n ©f hydrogen. Ignition to a free flame in
air results in quiet burning (22).
Water s©luti©ns of the bor©hydride are stabilized up
to the reflux temperature by the addition of base. The ma
terial is soluble in water, alcohol and liquid ammonia and
generally insoluble in ethers and hydrocarbcns.
It was reported that the aromatic nitro group is re
sistant to attack by potassium borohydrlde (13, 23). As is
sodium b©r©hydride, potassiiim b©r©hydride is used mainly for
the reduction of carbonyl groups (24).
11
Reduction with Lithium Borohydrlde
Lithium b©r©hydride is a white crystalline salt-like
s©lid. It is quite hygr©sc©pic and may ©ccasicnally ignite
©n ccntact with water. The comp©und melts at 284° with de-
comp©siti©n. Pr©l©nged heating in vacu© ab©ve 200 als© re
sults in dec©mp©siti©n. The b©r©hydride is s©luble with
reaction in the lower alc©h©ls. The preferred s©lvent f©r
©rganic reducti©n is tetrahydrofuran; it is als© s©luble in
l©wer ethers and amines.
When nitr©benzene is refl\ixed with excess lithiiim
b©r©hydride in an ether-tetrahydr©furan mixture, 30^ ©f the
nitr©benzene is rec©vered al©ng with 22^ ©f aniline and 30^
©f an Intractable dark red ©11 (25). The reducti©n ©f p-
nitr©benzyl chl©rlde and 5-chl©r©methyl-l-nitr©naphthalene
with lithium hydride and a little lithium b©r©hydride in
tetrahydr©furan yields 7^ o^ p-nitr©t©luene and Sj^ ©f 5-
methyl-l-nltr©naphthalene respectively. In b©th cases 8-20^
of the azo compound is also formed (26).
Reducticn with Sodium Trimeth©xyb©r©hydride
Sodium trimethoxyb©r©hydride is readily prepared by
the reacticn ©f sodiuim hydride with trimethyl borate in the
presence of tetrahydrofuran as solvent (27).
NA"*" H " + B ( 0 C H J 3 ^ NA'^CB(0CH3)3Hr
12
It is insoluble in simple ethers, such as diethyl and di-n-
butyl, but is moderately soluble in dioxane and highly sol
uble in tetrahydrofuran. Brown and Meed (27) reported that
in diethyl ether, nitr©benzene was n©t attacked by s©diiim
trimethoxyb©rohydride, whereas in the boiling di-n-butyl
ether two moles of sodium trimethoxyb©r©hydride were c©nsumed
per mole of nitrobenzene. The nature of the reduction pro
duct was not investigated.
Reducti©n with S©dium Trieth©xyaluminumhydride
When m©n©meric aluminum ethylate is heated with s©dium
hydride in tetrahydr©furan at 70—75°* a complex, sodium
trieth©xyaluminumhydride, Na^l (OCgH-)^!^^, is rapidly f©rmed.
It is collected as gray powder but can be obtained as col©r-
less micr©crystalline p©wder. Its ethereal s©luti©n sh©ws
n© ion-conductivity even after the addition ©f pyridine,
which sh©ws the negligible diss©ciatlon ©f m©lecule. Never
theless the replacement ©f the s©dium i©n with certain cation
groups is possible.
(C6H5)3SNCI + NA CAI(0C2H5)3H) > NA"" Cr+ i;(C6H5)3SN)'"(AK0C2H5)3Hr
Its anion which shows krypton c©nfigurati©n can be c©nceived
as a hydride i©n stabilized thr©ugh the c©mplex-f©rmati©n
with alviminum alcoholate. It is thus made capable of attack
ing a polar multiple bond.
13
It is decomposed quickly by water and ©ther hydroxyl-
group containing comp©unds. The c©mplex and its s©luti©ns
are air-sensitive. F©r its applicati©n in reducti©n, the
original tetrahydrofuran s©luti©n fr©m the preparation is
utilized. Azobenzene is ©btained In 68^ yield fr©m the re-
duct i©n of nitrobenzene at 65° (28).
Reductive Coupling ©f Nitr© C©mp©unds
Miscellaneous Meth©ds
During the past several years various new methods ©f
reductive coupling ©f nitr© c©mp©unds, m©stly ©f the benzene
series, have been devel©ped. Am©ng them, the f©ll©wing are
©f the interest in c©nsidering their applicability to the
naphthalene series.
Reduction with Dib©rane
Brown and Subba Rao (29) have used diborane as a re
ducing agent for organic functional groups. It is different
from metal hydrides in that it is an acidic type of reducing
agent; it is believed to fimction throiigh an attack on am
electron rich center in the functional group. Dib©rane is
prepared by adding a s©luti©n of sodium borohydrlde in diglyme
to a solution of b©r©n trifluorlde etherate in the same s©lvent,
3NABH^+4BF3(C2H5)20 ^ZBgHg + SNABF^ + "^^^2^5)2^
14
and the gas ev©lved is swept by a current ©f nitr©gen gas
int© a diglyme ©r tetrahydr©furan s©lutl©n ©f the c©mp©und
t© be reduced.
Az©benzene is listed as a rapidly reduced c©mp©und,
c©nsumlng 1,9 m©les ©f dib©rane per m©le in ©ne h©ur, while
nitr©benzene is apparently reduced ©nly slightly.
Coupling ©f Organometallies by Nitr©us Oxide
Nitrous oxide reacts with primary, secondary amd ter
tiary alkyl lithium compounds and with most aryl lithium com-
p©unds. Pr©m the reacticn ©f phenyl lithium with nitr©us
oxide, lithium benzenediazotate, azobenzene, triphenylhydrazine
and phenol are obtained besides benzene and diphenyl. Berin-
ger, e_t aJ. (30), accounted the f©rraati©n ©f az©benzene and
triphenylhydrazine as the further reacticn ©f the first-f©rmed
lithiim benzenediaz©tate with m©re phenyl lithium. Pr©m phenyl
lithium and nitr©us ©xide, they ©btained a 4.8^ yield ©f phen©l,
7.25 ©f az©benzene and 21^ ©f triphenylhydrazine with small
quamtities ©f benzene, and diphenyl. With 1-naphthyl lithium
they obtained 3^ of l-naphth©l, 8.8j ©f naphthalene aind lOJ
of 1,1•-az©naphthalene with m©derate am©unts ©f a yell©w s©lid
which decomposed above 28O . The lithium-comp©unds were easily
prepau»ed from the corresponding brom©-c©mp©unds and metallic
lithium in absolute ether.
Meier obtained somewhat different results from the re
action of phenyl lithium with nitrous oxide; he obtained 7.85
15
of phenol, 305 of azobenzene, a moderate amount ©f diphenyl
and small am©unts ©f triphenylhydrazine, benzidine and hydra-
zobenzene. He explained the c©urse ©f f©rmation ©f the varl©us
c©mp©unds as f©ll©ws (3I).
N<N0U
"t-NgO ^(y
1 Li gO -1-
N=N
" ^ ^ ^ ^
NH-NH
" ^ ^ ^
N-N-Li Li
O r^^^^r-fT^
+ • ^ ^ i ^ ' ^ ^ ^ " ^ ^ ^ ^ ^
Hydr©gen©lysis ©f Nitro Gr©up
As early as in 1877, Klobuk©wski (5) indicated that
naphthalene was c©llected am©ng the ©ther c©mp©unds, such as
ammonia and a yellow oil, fr©m the destructive distlllati©n
©f nitr©naphthalene with lime. The residue ©f the distilla-
ti©n which melted at 275 was claimed as az©naphthalene by
him. The f©rmati©n ©f naphthalene was n©t rec©rded by his
precurs©r. Doer (4), in his destructive distillation of nitro
naphthalene with zinc dust. This fact has apparently been
16
left unconfirmed hithert©.
It is a well established fact that ©ne ©f the nitr©
gr©ups in o- ©r p-dinitr©benzene is easily replaceable with
electr©negative gr©ups. Evsms and Pry claimed t© have ob
tained o- and p-az©t©luene respectively from o- and p-dinitr©
benzene by the actl©n ©f magnesium-amalgam in ethaLn©l ©r
raethan©l (32). While the replaceability ©f nitr© gr©up by
an electr©negative methyl gr©up is, perhaps, feasible, the
entry ©f methyl gr©up fr©m b©th methaji©l and ethan©l is
questi©nable.
Antener (33) ©btained p,p*-dimeth©xyaz©benzene and
p-nitr©suiis©le fr©m the reacti©n ©f p-dinitr©benzene with
s©dium and methan©l. He viewed the replacement ©f ©ne nitr©
gr©up as taking place initially, f©ll©wed by subsequent re
duction of the other nitro group to the az© c©mp©und.
/r-\ N3X)CH3 / - \ / ^ \ ^ _ / ~ \ OCH3
Alth©ugh well-defined cases ©f the hydr©gen©lysis ©f
ar©matic nitr© gr©ups by complex metal hydrides have not been
reported in the literature, some examples exist in the alipha
tic series. Backer (34) obtained a small amount of
CH (SO^CH^)p from the action of lithium aluminum hydride ©n
0pNCH(S02CH^)p. Adams and M©Je (35) ©btained a 60^ yield ©f
bis-(l,4-naphthalenedibenzenesulf©namid©-2)-methauie by the
17
acti©n ©f lithium aluminum hydride on bis-(l,4-naphthalenedi-
benzenesulf©namld©-2)-nitr©methan©l. In the reducti©n ©f
l,2-dlnitr©-l,2-dlphenylethane with lithium aluminum hydride,
D©m©w and Fust (36) ©btained l-amin©-l,2-diphenylethane; ©ne
of the nitro groups was hydrogenolized while the other was
reduced to amino gr©up.
CHAPTER III
EXPERIMENTAL
Reducti©n with Lithium Aliminum Hydride
Preparati©n and Analysis ©f Lithivtm Aluminum Hydride S©luti©n
The lithium aluminum hydride used was a pr©duct ©f
Metal Hydrides, Inc©rp©rated (l8). It was a gray-white gran
ular p©wder ©f 95J purity. The ethereal s©lutl©n was pre
pared in a S©xhlet Extra©ti©n Apparatus; the lithium aluminum
hydride p©wder which was crushed carefully in a mcrtar was
extracted with b©iling anhydr©us ether f©r six t© seven h©urs.
The clear s©lutl©n thus f©rmed was st©red in a br©wn b©ttle
pr©tected by a calcium chl©ride drying tube and was kept in
a c©©l dark place.
Pelkin's meth©d (37) was used f©r the determinati©n
©f the c©ncentrati©n ©f lithium aluminum hydride s©luti©n.
The foll©wing s©luti©ns were prepared.
S©luble starch indicat©r s©luti©n.- A slurry ©f ©ne
gram s©luble starch was added t© 100 ml b©iling water. After
c©©ling, three grams ©f p©tassium iodide was added. The so-
luti©n was st©red in a br©wn b©ttle and the surface ©f s©lu-
tion was c©vered with a thin layer ©f t©luene in ©rder t©
keep fr©m bacteri©l©gical acti©n.
S©dium thiosulfate soluti©n,- Appr©ximately 25 g ©f
s©dium thi©sulfate pentahydrate and 0.2 g ©f anhydr©us s©dium
18
19
carb©nate were diss©lved in ©ne liter ©f water. This s©lu-
ti©n was standardized with weighed i©dine each time bef©re
use.
The standardizati©n ©f the s©dium thi©sulfate s©lutl©n
was carried ©ut as f©ll©ws: Ab©ut 0.5 g ©f i©dine was weighed
exactly to 0.1 mg and dissolved in 100 ml water c©ntaining
5 g of potassium iodide and 5 ml of Z% hydrochl©ric acid.
This was titrated with the s©dium thi©sulfate s©luti©n. When
the c©l©r of iodine almost disappeared, 2 ml of starch indi-
catcr s©luti©n was added and the s©luti©n was titrated exactly
to the point where the solutl©n turned t© c©l©rless. Dupli
cate titrati©ns were carried ©ut in every case.
Solution of iodine in benzene.- Approximately 52.3 6
of iodine was dissolved in one liter of anhydrous benzene.
The exact c©ncentrati©n ©f the iodine s©luti©n was n©t essen
tial, since an excess ©f s©luti©n was t© be used and back-
titrated with standardized s©dium thl©sulfate s©luti©n.
Titrati©n ©f lithium aluminum hydride s©luti©n.-
Exactly 2 ml ©f the ethereal s©luti©n ©f lithium aluminum
hydride was added as rapidly as p©ssible with shaking t© 20
ml ©f the iodine solution in amhydrous benzene. After add
ing a few ml of water and few drops of glacial acetic acid,
the mixed s©luti©n was titrated with the standardized s©di\im
thiosulfate s©lution with vig©r©us shaking. Tw© samples and
a blank were titrated f©r each batch ©f the lithium aluminum
hydride s©luti©n.
20
In the presence ©f excess i©dine, each m©le ©f lithium
aluminum hydride reacts with tw© m©les ©f l©dine t© f©rm
lithium i©dide and aluminum iodide with evoluti©n ©f hydr©-
gen.
LiAIH4 -I- 2 1 ^ ^ ^Hgt Lil -h AII3
Reducti©n with Lithium Aluminum Hydride (38)
Direct additi©n meth©d. The s©luti©n ©f lithium alum-
in\im hydride was placed in a three-neck flack equipped with
a mechanical stirrer driven by a spark-free m©t©r, a reflux
condenser, and a dropping funnel. Calcium chloride tubes
were attached t© the ©pen end ©f c©ndenser and funnel. The
ethereal s©luti©n ©f the comp©und t© be reduced was added t©
the stirred lithium alviminum hydride s©luti©n. After reacti©n
was c©mplete, ice water, alcne, ©r its mixture with ethyl ace
tate, was added t© dec©mp©se the ccmplexes. The resulting
mixture was treated as described later.
Extra©ti©n meth©d. l,l*-Az©naphthalene, being ©nly
slightly s©luble in diethyl ether, was placed in the thimble
of a Soxhlet apparatus and the s©lution ©f lithium aluminum
hydride was kept b©iling in the flask bel©w. After all ©f
the azonaphthalene was extracted, the mixture was treated
as described later.
Inverse addition meth©d. The apparatus was similar
to the direct addition method. The solution of lithium
21
aluminum hydride was added to the soluti©n ©f the c©mp©und
t© be reduced. The subsequent treatment was the same as pre
vious ones.
Reduction ©f Nitr©benzene
For the purpose ©f reducti©n "Chemical Pure" grade
nitr©benzene was dried ©ver anhydr©us calcium chl©ride ©ver-
night and distilled under reduced pressure; b.p. 101.5^/25
mm Eg.
NB-LAH-I. Lithium alTAminum hydride p©wder, 4.5 g
(0.12 m©le), was refluxed with 150 ml ©f abs©lute diethyl
ether f©r ©ne h©ur. After the s©lutl©n was c©©led t© r©©m
temperature, 10 g (0.08 m©le) ©f nitr©benzene in I30 ml ether
was added thr©ugh the dr©pping fiinnel s© as t© keep the s©lu-
tion refluxing gently. During the ccurse ©f additi©ri, a change
©f c©lor t© yellow, deep yellow, orauige amd finally red br©wn
was ©bserved. After the t©tal additi©n, the mixture was stir
red f©r ©ne m©re h©ur. Then 25 ml ©f ethyl acetate and 2 ml
of water were added for dec©mp©siti©n, and the c©ntents were
p©ured into 100 ml of ice-water. Seventy-five milliliters
of 105 sulfuric acid was added and the mixture was filtered.
The ether layer was separated from the filtrate and was eva
porated t© dryness ©n a steam bath. The slurry and water
portion were extracted with porti©ns ©f benzene until the
benzene was n© l©nger c©l©red. The residue fr©m the ether
layer was combined with the benzene extract. The benzene
22
soluti©n was ccncentrated and treated with charc©al. After
c©©ling, red-©rauige leaflets ©f az©benzene crystallized ©ut.
They were filtered and washed with c©ld benzene. Yield:
3 g (40.55^), m.p. 67-68°.
NB-LAH-II. The same am©unts ©f reactants were used
as ab©ve. At the end ©f reaction, 100 ml of ice water was
added foll©wed by acidificati©n with dilute sulfuric acid.
After the acid was added, the ether layer was separated, and
the aque©us layer was extracted with f©ur p©rti©ns ©f 25 ml
ether. The ether was evap©rated ©ff, and s©lid mass was
taken int© ethan©l and treated with charccal. The ©range-
red leaflets, az©benzene, weighed 4.2 g (56.7$ yield), m.p.
65-67^.
NB-LAH-III. Lithium aluminum hydride, 5.2 g (0.l4
m©le), was refluxed with 200 ml of diethyl ether for two
hours. The flask was immersed in a dry ice-acetone mixture
of -80°, and 11.0 g (0.09 mole) of nitrobenzene in I30 ml of
diethyl ether was added. The mixture was all©wed t© warm t©
ro©m temperature (over a period of 21 hours). Then, 70 ml
of ice-cold water was added to decomp©se the complexes and
the contents were poured into 100 ml ©f ice water. Subse
quent treatment as in NB-LAH-II yielded 4.4 g (58.4^) ©f the
final pr©duct, deep bright red leaflets, m.p. 66-68°.
23
Reduction of 1-Nitr©naphthalene
For the reduction of 1-nitr©naphthalene, the stan
dardized s©luti©n ©f lithiiim aluminum hydride was used. The
nltronaphthalene which was slightly br©wnish-yell©w, was ©b-
tained fr©m Dlstillati©n Pr©ducts industries (39). It was
dissclved in ethan©l and treated with charccal. The light
yell©w needles thus ©btained fr©m ethan©l melted at 6o°.
This was used in the f©ll©wing reducti©ns.
NN-LAH-I. The first batch ©f the lithiiom aluminum
hydride s©luti©n was prepared fr©m 7 g of lithium aluminiim
hydride extracted with 300 ml ©f abs©lute diethyl ether f©r
17 h©urs. Standardlzati©n ©f the lithium aluminum hydride
sh©wed it t© be O.I336 M.
1-Nitr©naphthalene, 3.5 g (0.02 m©le), in I50 ml ©f
diethyl ether was added dr©pwise t© 200 ml (0.026 ai©le) ©f
lithium aluminum hydride s©luti©n. After the additi©n, the
mixture was stirred f©r tw© h©urs. During the addlti©n and
the subsequent stirring, the c©lor ©f mixture changed fr©m
yellow to orange brown. At the end of stirring, 70 ml ©f
ice-cold water was added t© dec©mp©se the c©mplexes. When
the water was being added, the mixture turned purplish and
the ether layer finally became light red. The c©ntents ©f
the flask were poured int© 200 ml ©f ice water amd 100 ml ©f
20^ sulfuric acid was added. The ether layer was separated
amd evapcrated to dryness. The water layer was clear, yet
24
when it was extracted with benzene, a brown solid appeared
between the two layers. This solid was separated fr©m the
liquid phases by use ©f a centrifuge.
The residue fr©m the ether p©rtl©n was c©mbined with
the benzene extracts. A dark ©11, smelling of 1-naphthyl
amine, remained after evaporating ©ff the benzene. It s©lid-
if led upon washing with 10$ hydrochl©ric acid. After being
washed with water and dried, it weighed 1.8 g. Repeated
treatment with charccal in benzene and finally crystalllza-
ti©n from glacial acetic acid, gave a slightly brownish red
product 0.1 g, m.p. 188-190° (sublimed). The yield of the
final pr©duct ©f l,l»-az©naphthalene was 3.5^.
NN-LAH-II. P©ur grams ©f lithium aluminum hydride
was extracted with 300 ml ©f ether f©r five hours. The con-
centrati©n ©f the lithium alumin\im hydride 3©luti©n was
0.445 M.
1-Nitr©naphthalene, 6 g (0,035 m©le), in 90 ml ether
was added t© 100 ml (0.044 m©le) ©f the lithium aluminum hy
dride soluti©n kept at -76 . After 18 h©urs, the tempera
ture ©f mixture reached 4 and 70 ml of ice-cold water was
added. The contents were poured int© 100 ml ©f ice water
ajid the ether layer was separated and evap©rated. The water
solution and slurry were extracted with porti©ns ©f benzene.
The residue ©f ether layer was added t© the c©mbined benzene
extracts. The red s©lutl©n gave a dark ©11 when the benzene
was evap©rated ©ff ©n a steam bath. Subsequent treatment as
25
in NN-LAH-I yielded n© satisfactcry result, th©ugh traces of
both 1-naphthylamine and l,l»-az©naphthalene were believed
t© be present.
NN-LAH-III. 1-Nitr©naphthalene, 5 g (0.029 mole), in
70 ml diethyl ether was added dropwise t© 100 ml (0.044 m©le)
©f the lithium aluminum hydride soluti©n which was c©oled t©
-80 . After the additi©n, the mixture was stirred f©r ©ne
h©ur at -65° to -70°. Seventy milliliters of ethyl acetate
was then added. During the course of stirring and addition
of the ethyl acetate no c©l©r change was ©bserved. After
the additi©n ©f the ethyl acetate, hcwever, the c©l©r changed
int© red and the vig©r©us ev©lutl©n of gas was observed as
the mixture was warmed up to ro©m temperature. Apparently
n© reduction of 1-nitronaphthalene or decomp©siti©n ©f lithium
aluminum hydride took place at the temperature lower than -65°
As the temperature was raised, the dec©mp©siti©n ©f lithium
aluminum hydride ©ccurred suddenly acc©mpanied by s©me reduc
tion of 1-nitronaphthalene. The slurry was separated from
the solution and extracted with porti©ns ©f benzene. The
©riginal ether solutl©n was evap©rated and the residue was
combined with the benzene extract. The soluti©n was washed
with lOJ hydrochloric acid and water. After treatment with
charcoal 3.0 g (60^) of unreacted 1-nitronaphthalene was re
covered from ethanol; a small amount of a red oil was als©
©btained.
26
NN-LAH-IV. 1-Nitr©naphthalene, 3.8 g (0.022 m©le),
in 70 ml ether was added t© 50 ml (0.027 m©le) ©f the lithium
aluminum hydride s©lutl©n c©©led t© -76°. The mixture was
allowed to warm up to -30° in 3.5 hours and 50 ml of ethyl
acetate was added t© dec©mp©se the complexes. The mixture
showed no change in c©l©r during the c©urse ©f warming and
decomposition. However, when treated with acid, as in NN-
LAH-III, and extracted with benzene, the benzene deepened in
c©l©r amd finally became dark br©wn. By evap©rati©n and sub
limation most of the original 1-nitr©naphthalene was reccvered
with s©me intractable dark tar.
NN-LAH-V. 1-Nitr©naphthalene, 17.3 g (O.l m©le), in
150 ml ether was added dr©pwise int© 400 ml (0.2 m©le) ©f
lithium aluminum hydride soluti©n. The addlti©n was c©n-
tr©lled in such a mamner that tw© t© three dr©ps was added
each time and n© further s©luti©n was added until the ev©lu-
ti©n ©f gas had ceased. Five h©urs was taken f©r total addi
tion. During the course of addition a series ©f c©l©r change,
br©wnish ©ramge, reddish br©wn and dark br©wn, was ©bserved.
After the t©tal additi©n, the mixture was stirred f©r another
hour and 100 ml of ice-cold water was added for the decomp©-
siti©n. The cclor ©f the s©luti©n became lighter up©n the
additi©n ©f the water. The c©ntents were poured into I50 ml
of ice-water, and the ether layer was separated and evapora
ted. The residue ©f evap©rati©n was added t© the benzene
extract of water soluti©n and slurry.
27
The benzene s©luti©n was extracted with six 100 ml
p©rtl©ns of saturated oxalic acid s©luti©n and then washed
three times with 100 ml p©rti©ns ©f water. After evaporating
©ff the benzene, 2.94 g ©f a pitch-like substance remained.
By subllmati©n in vacu© (3 mm Hg) ab©ve 165°, 0.77 g (5.3^
yield) ©f bright red l,l'-az©naphthalene was c©llected.
After two crystallizations from glacial acetic acid, it melted
at 189-190°.
The oxalic acid extracts and water washings were com
bined and concentrated on a steam bath to about 200 ml. Steam
distillation, after making alkaline with sodium hydroxide so-
luti©n, f©ll©wed. The distillate was extracted with ether
and the ether solution was dried over amhydrous calcium chlo
ride for two days. After the calci\im chloride was filtered
off, dry hydr©gen chl©ride gas was bubbled thr©ugh amd the
resulting salt was filtered and washed with anhydr©us ether.
The free amine was liberated by neutralizati©n; it weighed
2.19 g (15.3y yield). Recrystallizati©n fr©m aque©us ethan©l
yielded 1.35 g* slightly purplish pr©duct, m.p, 48°.
NN-LAH-VI. Eight grams ©f lithium aliiminum hydride
was extracted with 250 ml ©f abs©lute ether f©r seven h©urs.
Standardizati©n sh©wed the c©ncentrati©n ©f lithium aluminum
s©luti©n t© be 0.8l4 M.
NN-LAH-V was repeated with 230 ml (0.2 m©le) ©f lithium
aluminum hydride s©luti©n and 17.3 g (0.1 m©le) ©f 1-nitro
naphthalene. After decomp©sing the reacti©n mixture with
28
ice-cold water, it was made acidic with 10^ hydr©chl©ric
acid. The ether was evapcrated ©ff fr©m the mixture at r©©m
temperature and the mixture was then steam distilled. A
red ©11 with naphthalene-like ©d©r was c©llected, and was
extracted with ether. The aquecus p©rtl©n was discarded.
After evap©ratlng off the ether, a red oil was ob
tained which was subjected to sublimation under atmcspheric _ ©
pressure at 80-90 . N© sizeable am©unt ©f s©lid was obtained,
although there was a smell of naphthalene on the condenser.
The red oil, remaining from attempted sublimation, weighed
2.0 g. When treated with concentrated hydrochlcric acid it
s©lidified. The s©lid after treatment with charccal and
crystallizaticn fr©m water weighed 1.0 g. One half gram ©f
this was diss©lved in 20 ml water and a few chips of ice were
added. Acetic anhydride, 5 nil, was added under vigor©us stir
ring f©ll©wed Immediately by 5 g anhydr©us s©dium acetate in
25 ml ©f water. (4o) After c©©ling, the white solid was
filtered and recrystallized from ethanol after treatment with
charcoal. The acetyl-1-naphthylamine thus formed melted at
158-159°.
The residue from steam distillatl©n was made alkaline
and steam distilled again. The distillate was extracted with
ether after saturating with s©dium chl©ride. The same treat
ment as in NN-LAH-V yielded 2.5 g of 1-naphthylamine hydr©-
chloride. Pree amine was liberated by neutralization of the
aqueous solution of naphthylamine hydrochloride with lOJ of
29
sodium hydroxide s©luti©n. The mixture was immersed in an
ice bath f©r five minutes and filtered by sucti©n. The s©lid
was washed with three p©rti©ns ©f 5 ml water; m.p. 48.5-50°.
The t©tal yield ©f 1-naphthylamine was 2.8 g (19.6^^).
The residue fr©m the sec©nd steam distillati©n was
all©wed t© stand and the supernatant liquid was siph©ned ©ff.
The s©lid was centrifuged and washed with lOJ hydr©chl©ric
acid several times and finally with water. The residue was
very dark in c©l©r. It weighed 11.16 g. Sublimati©n in ©
vacu© up t© 190 yielded n© az©naphthalene but a charred
residue.
NN-LAH-VII (Inverse addition). Lithium aluminum hy
dride soluti©n was prepared by the extra©ti©n ©f 3 g ©f the
s©lid with 150 ml anhydr©us ether. The soluti©n was f©und
t© be 0.525 M.
1-Nltr©naphthalene, 10.38 g (O.06 m©le), was diss©lved
in 150 ml ©f anhydr©us ether in a 1000 ml three-neck flask
which was immersed in a running-water bath at 20 , One hun
dred milliliters (O.O525 m©le) ©f the lithium aluminum hy
dride s©luti©n was added dr©pwise in 45 minutes. A series
of col©r changes was ©bserved. After the additi©n ©f 5 ml
of lithium aluminum hydride s©luti©n, the ©riginal light
yellow solution became turbid; this turbidity seemed to deepen
with further additi©n. When about two-thirds of the s©luti©n
was added, the c©l©r ©f the mixture was br©wnish yellow. At
the end of the t©tal addition, the col©r was br©wnlsh ©range.
30
One hundred milliliters of ice-water was added dropwise
after ten nsinutes of stirring. As the water was added, the
color of the mixture changed to orange and finally to deep
red. The mixture was acidified with dilute hydrochloric
acid and the ether was distilled off at room temperature
under reduced pressure.
The mixture was extracted with two 100 ml portions of
benzene. Some dark solid appeared between the two layers.
The benzene solution with dark solid in it was extracted
with two 100 ml portions of 10^ hydrochloric acid and then
was washed with three 50 ml portions of water.
All the acid extracts* ond washings were combined with
the aqueous part of the original reaction mixture, and were
made alkaline with sodium hydroxide solution and steam dis
tilled. About 1.3 liters of distillate was collected. The
distillate was made acidic with hydrochloric acid and extracted
with 100 ml, 70 ml and 70 ml of ether.
The ether solution was dried with amhydrous sodium sul
fate overnight. The ether was evaporated after filtering off
the sodiiim sulfate. The residue weighed 1.06 g, from which
0.0381 g (0.55 yield) of naphthalene was collected by subli
mation at atmospheric pressure from 80° to 90 . After treat
ment with charcoal and recrystallizatlon from ethanol it
melted at 79-2-81.2 (Literature 80.22°).
Hie residue remaining after sublimation was dissolved
in water, treated with charcoal amd evaporated to dryness.
31
giving 0.22 g of s©lid. This, with acetic anhydride gave
an acetyl derivative, m.p. 156-158° (literature f©r 1-naph-
thylaunlne derivative, 159°).
The aque©us part ©f the steam distillate was made
alkaline with s©dlum hydr©xide and extracted with 270 ml
ether in three porti©ns. The aque©us s©luti©n was discarded
and the ether extracts were dried with anhydr©us s©dium sul
fate ©vernight. Pr©m the same treatment as in NN-LAH-V, O.98
g ©f 1-naphthylamine hydr©chl©rlde was ©btained. The acetyl
derivative melted at I56-I58 . The tctal 1-naphthylamine
hydr©chl©ride was 1.2 g (11.2^ yield).
The benzene s©luti©n with suspended dark solid was
filtered by sucti©n. The s©lid was washed with six 20 ml
p©rti©ns ©f b©iling benzene and then with tw© 50 ml porti©ns
©f b©iling water. The benzene washings were c©mbined with
the benzene s©luti©n. The dark br©wn s©lid charred and burnt
sl©wly in a flairae, leaving a residue.
The benzene s©luti©n was evap©rated amd the resulting
dark ©11 weighed 4.3 g. By sublimati©n ab©ve I80 in vacu©
0.165 g (1.95^ yield) ©f 1,1'-azonaphthalene was obtained as
red needles. After recrystallizatlon from glacial acetic
acid it melted at l85-l88°.
The results of reduction ©f l-nitr©naphthalene with
lithiiom al\aminum hydride are summarized in Table I.
32
TABLE I
THE REDUCTION OP 1-NITRONAPHTHALENE WITH LITHIUM ALUMINUM HYDRIDE
1-nitr©-naphtha-
Expt.lene N©. (m©le)
Lithium aluminum hydride
% m©le)
Temperature
Pr©ducts and yields
0.02
0.035
0.024
0.022
0.1
0.1
0.06
0.026 25
0.04
0.044
0.027
0.2
0.2
-76 t© 4
-70 t© -65
-65 t© -30
25
25
0.0525 20
1-Naphthylamine, n©t separated. l,l*-Az©naphthalene, 3.5^. Dark br©wn s©lid, main pr©duct.
1-Naphthylamine, trace. 1,1*-Az©naphthalene, trace, Dark brcwn s©lid, main pr©duc t.
1-Nitr©naphthalene, 60^ rec©very. Red ©11.
Tar 1-Nitr©naphthalene, rec©vered.
l,l*-Az©naphthalene, 5.3^. 1 -Naphthylamine, 15.35 . Dark br©wn s©lid.
1-Naphthylamine, 19.6%. Naphthalene, trace. Dark br©wn s©lid.
Naphthalene, 0.5^. 1 -Naphthylamine, 11. 2 . 1,1* -Az©naphthalene, 1.955 . Dark br©wn s©lid.
33
Reducti©n of 5-Bromo-l-nitronaphthalene
Lithium aluminum hydride, 5.2 g (0.I3 mole), was re
fluxed with 100 ml of anhydrous ether for ©ne h©ur, and then
immersed in am ice bath. Ten grams (0.04 m©le) ©f 5-br©m©-
l-nitr©naphthalene in 250 ml ©f amhydr©us ether was added in
thirty minutes. The mixture was stirred f©r tw© m©re h©urs
at ro©m temperature. Sufficient water was then added to de
compose complexes. The ether layer was separated and evapor
ated to dryness. The water layer was extracted with benzene
and the residue from ether soluti©n was added t© the benzene
extract.
The benzene extract was washed with lOJ hydr©chl©ric
acid followed by water. The washings and the solid which
appeared in washing were combined.
The benzene soluti©n free from amine was evaporated
to dryness. A dark col©red solid, weighing 6.85 g, was ob
tained from which 2 g (22.8j ) at first tho\ight t© be 5,5*-
dibr©m©-l,l*-azonaphthalene, m.p. 222.5-223.5 , was obtained
after treatment with charcoal and recrystallizati©n fr©m
benzene. Bogoslovskii amd Kazok©va (4l) gave 210 as the
melting p©int of 5,5*-dibr©m©-l,l*-az©naphthalene; h©wever,
according to Mr. R. L. Snell (42) the melting point of the
azo is 274-275° while the melting point of the azoxy is 210 . ©
Analysis (43) of the comp©und, m.p. 222.5-223.5 showed that
this compound is neither the expected azo- nor azoxy compound
34
It is possible that the comp©und ©btained is a m©lecular c©m-
plex of the azo- and az©xy.
Pound: c, 53.57; H, 2.69; N, 6.17; Br, 35.83^. Calcd. for azo: c, 54^57; H, 2.75; N, 6.37; Br, 36.31^. Calcd. for azoxy: C, 52.66; H, 2.65; N, 6.l4; Br, 35.04^.
Reduction of l,l'-Az©naphthalene
AN-LAH-I. 1,1'-Azonaphthalene, 1.15 g (0.004 mole),
was stirred in 350 ml of anhydrous ether. Not all of the
comp©und dlss©lved. This mixture was added t© 20 ml (O.Ol
m©le) of lithium aliimin\im hydride solution, c©©led t© -78°
in a dry ice-acet©ne bath. The temperature was then allowed
to rise to -10° in 28 hours. No color chamge was observed.
At the end of 28 hours, 50 ml of ethyl acetate was added.
The ethyl acetate was evaporated off and the mixture was
acidified with lOJ hydrochl©ric acid. The red s©lid was fil
tered and washed with acid and water. The ©riginal 1,1'-
az©naphthalene was all rec©vered, m.p. 189-190*^.
AN-LAH-II, l,l'-Az©naphthalene, 1,11 g, was placed in
the thimble ©f a S©xhlet extraction apparatus. Fifty milli
liter (0.027 mole) of lithium aluminum hydride solution was
kept boiling in the flask underneath for nine h©urs. N© ap
preciable change ©f c©l©r was ©bserved during refluxing.
After the refluxing, the mixture was treated as ab©ve. The
total original azonaphthalene was recovered, m.p. 189-190°.
35
Reduction with S©dium B©r©hydride
Materials
Sodium b©r©hydride used in the f©ll©wing reducti©ns
was ©btained fr©m Metal Hydrides, Inc©rp©rated (l8). It was
a white p©wder ©f 98^ purity. Diglyme (diethylene glyc©l
dimethyl ether) was the pr©duct ©f The Mathes©n C©mpany, In-
corporated (44). It was placed over s©lid s©dium b©r©hydride
©vernight and distilled.
Standardizati©n ©f S©dium B©r©hydride S©lutl©n
A s©luti©n was made ©f 10.35 g of s©dium b©rohydride
in 200 ml ©f diglyme; the s©lutl©n was filtered.
The f©ll©wing s©luti©ns were prepared.
S©dium thi©sulfate s©luti©n, 0.1 N, Twenty-five grams
©f s©dium thi©sulfate pentaJiydrate and 0,2 g ©f anhydr©us
s©dium carbonate were dissolved in ©ne liter ©f water.
Sulfuric acid, 4 N. Fifty milliliters ©f ccncentrated
sulfuric acid (36 N) was diluted t© 450 ml.
P©tassium i©date s©luti©n, 0.25 N. P©tassium i©date,
52.1754 g, was diss©lved in water and made up t© 250 ml in a
volumetric flask.
Duplicate analyses ©f the s©dlum thi©sulfate s©luti©n
gave 0.09952 N and 0.1014 N; average 0.1004 N.
For the standardization of sodium b©r©hydride s©luti©n
(45), 100 ml ©f the borohydrlde s©luti©n was taken and added
36
t© 50 ml ©f 0.25 N p©tassium i©date s©luti©n. The excess
i©date was back titrated with standardized scdium thl©sulfate
s©luti©n. Duplicate samples were taken; 34.96 ml amd 35-01
ml ©f the thi©sulfate s©luti©n were ccnsumed respectively,
which averaged 34.98 ml. The scdium b©rohydride, therefore,
contained 42.53 mg/ml.
Reduction ©f 1-Nitr©naphthalene
NN-NBH-I. Three grams (0.075 m©le) ©f s©dium b©r©-
hydride was placed with 30 ml ©f diglyme in a 250 ml flask
equipped with a reflux c©ndenser and a therm©meter. Ten
grams (O.058 m©le) ©f 1-nitronaphthalene was added while the
sodium bor©hydride was n©t c©mpletely diss©lved. Heat was
ev©lved and a vig©r©us reacti©n ©ccurred. The temperature
reached 210° and the mixture became dark c©l©red. After
this vig©r©us reactl©n, the temperature dr©pped and the mix
ture was heated at 90-100° f©r 22.5 h©urs. Sufficient water
was added to dec©mp©se the excess s©dium b©r©hydride, f©ll©wed
by acidification with hydrochloric acid. The mixture was then
steam distilled in order to remove diglyme.
In the distillate s©me white s©lid was c©llected which
smelled ©f naphthalene. Ab©ut 300 ml ©f the distillate was
collected. After being in a refrigerator overnight, the dis
tillate was filtered by sucti©n. A small am©unt ©f pinkish
s©lid was ccllected. It was dec©l©rlzed in an etham©l s©lu-
ti©n and recrystallized fr©m aqueous-ethan©l. Platelike
37
crystals with a strong naphthalene odor were obtained; m.p,
78-80°,
The residue from the steam distillati©n was made al
kaline with sodium hydroxide s©lution and steam distilled
again. The distillate smelled ©f naphthylamine and diglyme.
A large am©unt ©f ether was used t© extract the distillate
and the water layer was discarded. Dry hydrcgen chlcride
gas was passed thr©ugh the ether s©luti©n, after drying ©ver
anhydr©us s©dlum sulfate, and the resulting 1-naphthylamine
hydr©chl©ride was filtered. The hydr©chl©ride smelled of
diglyme. After neutralization with sodium hydroxide soluti©n,
a precipitate of amine was obtained which was not further
worked-up.
The oily substance in the hot residue of steam dis
tillation solidified upon c©©llng. It weighed 4.08 g. When
sublimed in vacu© up t© 170°, a small am©unt ©f naphthylamine
was collected. The solid was dissolved in hot benzene and
dissolved material was filtered off. After evaporating off
the benzene, 2 g of dark red substance was left behind. By 0
the sublimati©n of this dark red substamee up to 190 in
vacuo, about 0.2 g of yellow substamce was collected. It
o © melted between I30 and 175 . Crystallizati©n from ethyl
acetate gave a fine, yellow, neutral c©mp©und, m.p. 213-214°;
analysis (43) gave
H 6.68; C 82.48; N 9.75^
38
NN-NBH-II. Eighty milliliters (0.06 m©le) ©f the
s©dium b©r©hydride s©luti©n was placed in a 500 ml three-
neck flask Immersed in an ice bath. Ten grams (O.058 m©le)
of 1-nitronaphthalene in 35 ml diglyme was added under mechan
ical stirring and the mixture was warmed slowly to r©©m tem
perature. After 18.5 h©urs ©f stirring I50 ml ©f water was
added f©ll©wed by lOJ hydr©chl©ric acid t© make acidic. The
mixture turned dark red and then tarry br©wn. It was steaun
distilled.
Ab©ut 1.5 1. ©f the distillate was c©llected. Plate-
like crystals appeared as the distillate was c©©led. The
distillate was filtered by sucticn. Crude naphthalene weighed
0.5^ g (7.3^ yield). After dec©l©rizatl©n amd recrystalliza-r. o
tion from ethanol it weighed 0.23 &> m.p. 81 .
The distillate which was collected fr©m the steam dis-
tillati©n of the alkaline s©luti©n was c©mbined with the ab©ve
1-naphthylamine, made acidic with hydr©chl©ric acid and the
water was distilled ©ff under reduced pressure. The residue
was diss©lved in h©t water and treated with charc©al, amd
crystallized. It weighed 3.05 g (29^ yield). Free amine
liberated with s©dium hydr©xide melted at 48 .
The residue fr©m steaun distillatl©n was acidified and
extracted with benzene. A dark s©luti©n was ©btained which
gave 2.97 g of tarry substamce after evap©rati©n. It was
dissolved in benzene, chlor©f©rm amd acetic acid c©nsecutive-
ly amd treated with charc©al, but n© c©l©r impr©vement was
39
©bserved. Fr©m sublimati©n under reduced pressure up t©
190° ©nly a little dark-red ©11 was ©btained,
NN-NBH-III. 1-Nitr©naphthalene, 10 g (O.O58 m©le),
in 50 ml ©f diglyme was added int© 55 ml (0,063 m©le) ©f the
diglyme s©lutl©n ©f s©dium b©r©hydrlde c©©led t© 0°, Even
th©ugh the reacti©n flask was immersed in an ice bath, a
n©tlceable ev©luti©n ©f gas was ©bserved amd the c©l©r ©f
mixture changed gradually fr©m the ©riginal light yell©w t©
br©wnish yellew. After 25 hours ©f stirring the ev©luti©n
©f gas appeared to have ceased. The mixture was stirred f©r
three m©re h©urs at r©©m temperature and then 35 ml ©f water
was added dr©pwlse. At the end ©f reacti©n, the c©l©r ©f
the mixture was a transparent, deep red. After the additi©n
of water, it became a brownish red. The whole content of
the flask was vacuum distilled at 2 mm Hg t© rem©ve diglyme,
N© naphthalene was smelled in the distillate. The residue
was then diluted with water amd the gummy dark red substance
fl©ating ©n the surface of liquid was skimmed off. After suc
cessive washings with water the gummy material solidified.
The washings were returned t© the aque©us s©luti©n fr©m which
the solid had been removed. The selid weighed 7 g.
The liquid, which was turbid yell©w, did n©t smell ©f
naphthalene, but up©n acidifying it devel©ped the smell ©f
naphthalene and s©me s©lid precipitated. The precipitate was
filtered ©ff and s©dium hydroxide s©luti©n was added t© the
filtrate. It becaime red brown amd still smelled of naphthalene.
40
The liquid was acidified again and vacuum distilled. Naph
thalene was collected from the distillate, 0.043 g (0.58j
yield), m.p. 79-80°.
The brown solid fr©m the ©riginal mixture was not af
fected by dilute acid. It burned with a bright s©©ty flame;
©n prolonged heating it burned completely leaving no residue.
It was slightly s©luble in ethan©l, diethyl ether and s©luble
in benzene, ethyl acetate and cencentrated sulfuric acid.
Digesti©n of some of the s©lid with 4 N sulfuric acid, f©l-
l©wed by steam distillati©n gave s©me yell©w needles ©f
1-nitr©naphthalene, m.p. 58-60 . Vacuum sublimati©n ©f s©me
©f the s©lid gave only a small amount of red oil. !nie solid
dec©mp©sed ab©ve I50 . It was ©bvi©usly ©rganic in nature,
but n© inf©rmati©n was ©btained c©ncerning the type ©f c©m-
p©und.
The results ©f s©dium b©r©hydride reducti©n ©f 1-nitr©-
naphthalene are summarized in Table II.
41
TABLE II
THE REDUCTION OF 1-NITRONAPHTHALENE WITH SODIUM BOROHYDRIDE
Expt N©.
l-Nltr©-naphthalene (m©le)
S©dium b©r©-hydride (m©le)
Temperature
0.058
0.058
0.058
0.075
0.063
0.063
210, 90-100
25
0 t© 25
Pr©ducts and yields
Naphthalene, undetermined. 1-Naphthylamine, undetermined. Yellcw needle. Br©wn s©lid.
Naphthalene, 7.3^. 1-Naphthylamine, 29$ . Br©wn s©lid.
Naphthalene, 0.58^. 1-Naphthylamine, not is©lated, Br©wn s©lid, 7 g.
Reduction of p-Dinitr©benzene
p-Dlnitrobenzene, 0.5 g* in 10 ml of chl©r©f©rm was
added to one gram of sodiiom b©r©hydride and a few pellets ©f
s©dium hydroxide in 30 ml ethanol. After being kept at ro©m
temperature f©r 26 h©urs, the ©range-red mixture was acidi
fied with 10^ hydr©chlorlc acid. After the ©rganic s©lvents
were evap©rated ©ff, the mixture was made alkaline amd ex
tracted with ether. After evaporating ©ff the ether, a
yellowish brown solid remained which had a cinnamon odor.
After the treatment with charcoal and recrystallizatlon from
alcohol-ethyl acetate mixture, deep yellow needles with a
42
melting point of 189-192° were obtained. The melting p©int
©f 4,4'-diamin©az©xybenzene is 190° (46),
Attempted Hydr©gen©lysis ©f 1-Naphthylamine
The 1-naphthylamine used in this reacti©n was purified
fr©m dark "Technical Grade" 1-naphthylamine, The dark 1-
naphthylamine was dissclved in ether and precipitated as the
hydr©chl©ride with dry hydr©gen chlcride gas. The precipi
tate was filtered and washed with ether until the washing was
no longer c©l©red. The s©lid was dried and diss©lved in b©il-
ing water. The s©luti©n was treated with charc©al three times
t© ©btaln a col©rless s©luti©n. Free amine was liberated by
neutralization with dilute sodium hydr©xide s©luti©n. The
white needles were filtered and washed with dilute aque©us ©
ethamol, m,p. 50-51 .
Purified 1-naphthylamine, 3.1^ g (p.022 mole), in 25
ml ©f diglyme was added t© 1,2 g (O.03 m©le) ©f s©dium b©r©-
hydride in 25 ml ©f diglyme at r©©m temperature. After stir
ring at ro©m temperature f©r 23 h©urs, the mixture was heated
at 70^ f©r 5 hours. Water was added t© dec©mp©se c©mplexes
and the mixture was acidified with saturated ©xallc acid s©-
luti©n. Vig©r©us ev©luti©n ©f gas was ©bserved as water and
acid were added. The mixture was steam distilled. Naphtha
lene was not smelled in the transparent distillate.
The residue from steam distillation was made alkaline
and extracted with ether. The subsequent treatment of the
43
purple solution gave 2.73 g (69.7^ recovery) of 1-naphthyla
mine hydrochloride. The free amine liberated melted at 48-
50°.
Reduction with P©tassium B©r©hydride
Potassium bor©hydride used in the f©ll©wlng reducti©ns
was ©btained from Metal Hydrides, Inc©rp©rated (l8). It was
a white crystalline p©wder ©f 95^ purity.
Determinati©n ©f Purity of P©tassium B©r©hydride
The same method (45) as used in the determination of
the c©ncentrati©n ©f s©dlum b©r©hydride s©luti©n was used.
Potassium b©r©hydride, 0,0230 g, was diss©lved in 25 ml ©f
0.5 N s©dium hydr©xide. T© this s©luti©n 50 ml ©f 0.25 N
potassium iodate s©luti©n was added. The am©unt ©f 0.1004
N of sodium thiosulfate soluti©n used in the titrati©n was
92.19 ml. The purity ©f p©tassium b©r©hydride p©wder was
100 (50 X 0.25 - 92.19 X 0.1004) X 6.744 0.0230
- 95.0^
Reducti©n of Nitrobenzene
Potassium borohydrlde, 10.0 g (0.I8 mole), was sus
pended in 150 ml of methan©l c©ntaining a few pellets of
potassium hydroxide. To this suspension, 11,07 g (O.09 mole)
of nitrobenzene in 50 ml of ethamol was added and the mixture
44
was heated under reflux for 46 hours. After the mixture was
co©led, dilute hydr©chl©ric acid was added dr©pwise until n©
m©re evoluti©n ©f gas was ©bserved. At the end of reaction,
the color of mixture was ©range. The mixture was extracted
with ether. The ether was separated and evap©rated ©ff and
the residue was chilled in an ice bath. An ©range wax-like
substance was formed which failed to crystallize. The sub
stamce was steam distilled. Unreduced nitr©benzene was dis
tilled ©ff first, f©ll©wed by az©xybenzene, which s©lidifled
up©n standing. The s©lid was filtered and dried in a vacuum
desiccat©r; 5,98 g (67^ yield) was ©btained. Dec©l©rizing
in ethfim©l amd recrystallizing fr©m petr©leum ether gave
light ©range needles of melting point 34-36°; 5,17 g (58.0^
yield).
The above reduction was repeated with the addition of
s©di\im hydroxide instead of potassium hydroxide to stabilize
potassium b©r©hydride. The yield ©f az©xybenzene was 11%,
Reductl©n ©f 1-Nitr©naphthalene
NN-KBH-I. 1-Nitr©naphthalene, 10 g (0,058 mole), and
4 g (0,07 mole) of potassium bor©hydride were stirred int©
250 ml of methanol which was purified previously to free from
acetone. The soluti©n was heated under reflux f©r 2 h©urs,
Alth©ugh the solution became darker as the result of heating,
it still smelled of 1-nitronaphthalene. Dilute hydrochl©ric
acid was added after cooling at the end of refluxing. The
45
mixture was filtered and the solid residue was washed with
water. No precipitate was observed as the filtrate was
neutralized with sodium hydroxide soluti©n, which indicated
that n© 1-naphthylamine was f©rmed.
The s©lid remaining fr©m filtratl©n was sublimed t©
give 7.86 g (78.6^) ©f crude l-nitr©naphthalene. The residue
of sublimation was tar-like substance. The crude nltronaph
thalene was dissolved in ethamol and treated with chare©al
and recrystallized; it weighed 7.05 g, m,p, 56-59 .
NN-KBH-II. P©tassium b©r©hydride, 3,5 g (0,06l5 m©le),
with ©ne graim ©f s©diiim hydroxide was suspended in 100 ml of
a mixed solvent which was comp©sed ©f 30 ml ©f water, 30 ml
of methanol and 50 ml of ethanol. T© this was added 6,15 g
(0,0355 mole) of 1-nitronaphthalene in 100 ml ©f etham©l amd
the mixture was stirred at r©©m temperature f©r 4o h©urs.
Then 25 ml of lOJ hydr©chl©ric acid was added t© the reacti©n
mixture, which was br©wnish red in c©lor. The mixture was
filtered and the filtrate was c©ncentrated under reduced pres
sure at r©©m temperature. The dark br©wn substamce which ap
peared upon concentration was filtered amd washed with water;
it smelled of naphthalene.
The filtrate and washings were combined and neutralized
with s©dlum hydroxide s©luti©n amd the white precipitate was
extracted with ether. By the usual treatment 0,48 g {1,1%
yield) ©f 1-naphthylamine hydr©chl©ride was ©btained. The
acetyl derivative melted at 157.5-159 .
46
All solids were combined amd dissolved int© h©t ethyl
acetate. A brown solid, 1.10 g, was obtained after treating
with a large amount ©f charccal. Sublimati©n ©f this yielded
0.50 g (8,15 rec©very) ©f 1-nitr©naphthalene, Dec©l©rizati©n
and recrystallizati©n yielded yellew needles of melting point
56.5-58°.
NN-KBH-III. The reduction was carried ©ut as in
NN-KBH-II with 3,5 g (0,02 m©le) ©f l-nitr©naphthalene ex
cept s©dium hydr©xide was n©t added. The reactien mixture
was kept stirring f©r 48 h©urs at 15-20°, It was then poured
into 200 ml of ice-cold dilute hydrochl©rlc acid. After the
ev©luti©n ©f hydr©gen had ceased, the mixture was filtered
and the precipitate (A) was washed with water.
The filtrate and washings were c©mbined and steam
distilled after making alkaline. White needles, 0,11 g,
which were first assumed t© be 1-naphthylamine were ccllected
from the distillate. After recrystallizing from ethanol, the
l©ng pinkish needles melted at 96-97 . A mixture with 1-
naphth©l showed a great melting point depressi©n; the mixture
melted from 59° to 98 , The melting p©int ©f 1-naphthol is
94° (47). Not enough c©mp©und was ©btained f©r further iden
tification.
The precipitate (A) was dark brown, weighed 4.47 g.
It decomp©sed ab©ve 250 . It yielded n© az©naphthalene by
sublimati©n and did n©t change c©l©r up©n treatment with
charc©al. A dark tar with an ©d©r of 1-naphthylamine remained
47
after the evaporati©n ©f its benzene extract, 1-Nitr©naph-
thalene, weighing 0.12 g, was ©btained fr©m steam distilla-
ti©n, m.p. 56.5-58°,
NN-KBH-IV. P©tassium b©r©hydride, 3,5 g (0,062 m©le),
was diss©lved with ©ne gram ©f detergent in 50 ml ©f water.
To this s©luti©n 6.25 g of 1-nitronaphthalene in 50 ml ether
was added. The detergent was added to emulsify two immiscible
phases. The soluti©n was b©iled f©r 44 hours. The total ©ri
ginal comp©und was recevered unchanged.
The results ©f the reducti©n ©f l-nitr©naphthalene
with potassium borohydrlde are summarized in Table III.
48
TABLE III
THE REDUCTION OF 1-NITRONAPHTHALENE WITH POTASSIUM BOROHYDRIDE
Potassium bor©-
Expt, hydride No. (mole)
3
4b
l-Nltronaphthalene
(mole)
Temperature
Products amd y ie lds
0.07
0.062
0.062
0.062
0.058
0.036
0.02
0.036
l-Nltronaphthalene, 65 18.6% recovery.
Tar
1-Naphthylamine, 7.7^ 80 1-Nitr©naphthalene,
8.1^ reccvery.
White needle, 15-20 m.p. 96-97 , 0.11 g.
Dark br©wn s©lid.
100 1-Nitr©naphthalene, 100^ recevery.
a.-One graun ©f s©dium hydr©xide was added. b.-One gram ©f detergent was added.
Reducti©n ©f p-Dinitr©benzene
DNB-KBH-I. p-Dinitr©benzene, 5 g (0.03 m©le), was
extracted in a S©xhlet extra©tl©n apparatus with 200 ml ©f
b©iling ethan©l c©ntaining 15 g (O.26 m©le) ©f potassium
bor©hydride with few pellets ©f potassium hydroxide. The
col©r ©f s©luti©n turned int© green, dark green, red amd
finally brownish red. After 48 hours the mixture was c©©led
in an ice bath and acidified with dilute sulfuric acid. The
brownish precipitate was filtered amd washed thor©ughly with
water to remove inorganic substances, leaving a dark red
49
powder.
The dark red am©rph©us p©wder weighed 3,21 g. It was
degested with benzene and filtered. The dark red p©wder
(A), weighing 1.40 g, remaining was ins©luble in acid, base,
ethan©l, or diethyl ether. It was slightly soluble in ben
zene and nitr©benzene, and soluble in concentrated sulfuric
acid with deep blue coloration. It ignited Instantly when
brought to a flame and the black residue burned ©ff even
tually. Qualitative analysis shewed the presence ©f nitro
gen without halogen. It was stable up to 360 but charred
at higher temperature. It was reduceable with tin and hydro
chloric acid to form a colorless compound. On the assumption
that an amine was formed by the reduction, an acetyl deriva
tive was prepared directly from the reduction mixture and its
melting point was compared with N,N'-diacetyl-p-dlaminoben-
zene. The acetyl derivative of reduction product melted at
306.5-307° while that of authentic N,N»-diacetyl-p-dlamino-
benzene was also 306.5-307 . Analysis (43) of the red solid.
Found: C, 65.64; H, 4.19; N, 22.69^. Calcd. for ^2^'^19^1^2' ^' ^5.89; H, 4.38; N, 22.42^.
Calcd. for Cgi^H^^N^O^: C, 66.19; H, 3.94; N, 22.52^.
The benzene washings of the red powder was evaporated
to dryness. The residual red solid weighed I.81 g. By sub
limation at 80-90 in vacuo, O.15 g ©f yellewish needles
were ©btained. The residue ©f sublimati©n appeared t© be
TKXAS TECMNOUHilCAL CULLBGK LWBAJCfc
LUBBOCK. TEXAS
50
the saime red powder as above. The yellow needles were de-
colorized and recrystallized from ethamol. White needles
having a melting point of 58-61.5° was obtained. They were
neutral, s©luble in h©t ethanel and ccntained nitr©gen. Ele
mental analysis (43) sh©wed the substance t© be p-nitrophene-
t©le; 3.2^ yield.
Pound: C, 57.62; H, 5-46; N, 8.62%, Calcd, for CgH^NO^: C, 57.48; H, 5.46; N, 8,38 ,
The acidic filtrate from the original mixture was
evaporated on a steam bath to remove ethanol, A brownish
yell©w solid was filtered and washed with water, weighing
0.25 g. By sublimation, yellow needles having a melting
p©int ©f 112-114,5° was ©btained, N©t en©ugh c©mp©und was
©btained f©r further Identificaticn.
The ab©ve reacti©n was repeated with©ut the additi©n
©f p©tassium bor©hydride, i,e,, 5 g of p-dinitr©benzene was
extracted in a Soxhlet extraction apparatus with 200 ml of
boiling ethanol containing few pellets of p©tassium hydr©xide
for 48 hours, p-Nltrophenetole, 2,3 g, was ©btained by the
same treatment as ab©ve, m.p. 58-60 (46.3^ yield).
DNB-KBH-II. Fifteen grams ©f potassium b©r©hydrlde
was suspended in 100 ml of N,N*-dimethylanillne under mechan
ical stirring. To this suspension, a solution of 5 g of
p-dinitrobenzene in the same s©lvent was added. The color
©f p-dinitr©benzene s©lution was dark red; the c©l©ratlon
51
resulted as s©©n as the s©lute was disselved in the selvent.
The mixture was stirred at 90-100 f©r 43 h©urs. After c©©l-
ing to ro©m temperature, 150 ml ©f ^% hydr©chloric acid was
added dr©pwise.
The mixture was made alkaline and steam distilled t©
rem©ve dimethylaniline and unreacted p-dinitr©benzene. The
s©lld residue of steam distillation was filtered off amd
washed with water thor©ughly t© rem©ve any contaminating
inorganic material. The solid was dark in col©r, weighing
1.69 g. It was washed pertionwise with 70 ml ©f b©lllng ben
zene. The residue ©f benzene washing was brewn c©l©red p©w-
der, weighing 0,12 g, which burned sl©wly with©ut residue.
It did n©t have melting peint but charred ab©ve 220°.
Tw© different f©rms of solid crystallized out from the
benzene washing after it had been cooled: (A) an orange
powder, weighing O.2327 g amd (B) red needles, weighing
0,732 g. Repeated crystallization of the tw© separated s©lids
revealed that b©th had tw© different s©lld f©rms, red needles
and copper leaflets, depending on the conditi©ns ©f crystal-
llzati©n. B©th s©lids had a melting point of 215-217°. Their
mixture showed no melting point depression. Analysis (43)
showed them to be 4,4'-dinitroazobenzene (38.8^ yield).
Found: C, 53-35; H, 3.17; N, 20.35^. Calcd. for C^2%^4^2- ^' 53.07; H, 2,96; N, 20.58$ .
52
Reduction with Lithium B©r©hydride
The lithium bor©hydride, which was a micr©crystalline
p©wder, was a pr©duct ©f Metal Hydrides, Inccrporated (l8).
NN-LBH-I. Lithium b©r©hydride, I.06 g (0.046 m©le),
was refluxed with 50 ml ©f anhydr©us ether f©r 30 minutes.
1-Nltr©naphthalene, 8.46 g (0.049 m©le), in 100 ml ether was
added and the mixture was heated t© gentle reflux f©r 40 h©urs.
At the end of refluxing, the mixture was a cloudy, deep yellow.
The mixture was c©©led amd 100 ml of ice-water was added; it
changed int© a clear ©range s©luti©n up©n the additien ©f the
water, A gummy ©range material separated ©ut up©n acidiflca-
tl©n with hydr©chl©ric acid. The mixture was thus separated
int© three parts: (A) acid aque©us s©luti©n, (B) ether
extract of the above gummy precipitate, (C) benzene s©luti©n
which c©ntained substances inscluble in ether.
The acidic s©luti©n (A) was c©ncentrated on a steam
bath and then steaim distilled after making alkaline. The
usual treatment gave 0.42 g (0.48 ^ yield) ©f 1-naphthylaunine
hydrochloride. The free amine ©btained subsequently melted
at 47-49°.
The ether s©luti©n (B) was evaperated t© dryness. The
residue appeared as a red ©11 smelling ©f naphthalene. H©w-
ever further treatment with charcoal and repeated recrystal
lizatlon yielded only 1-nitronaphthalene O.06 g, m.p. 56-58°.
The tar obtained after evaporation of the benzene so-
53
lution (C) gave a trace ©f 1-nitronaphthalene contaminated
with red oil. After the removal of 1-nitronaphthalene, the
red oil smelled of naphthalene. However n© naphthalene c©uld
be crystallized ©ut fr©m the red ©11.
NN-LBH-II. The tetrahydrefuran used in this and the
f©ll©wing experiments was ©btained fr©m Dlstillati©n Pr©ducts
Industries (39). It was placed ©ver selid s©dium hydr©xide,
redistilled and stored over s©dium metal.
l-Nltronaphthalene, 8,25 g (0,045 mole), in 30 ml
tetrahydrofuran was added to the s©lutl©n ©f 1,43 g (0.066
mole) of lithium bor©hydride in 40ml ©f tetrahydrofuran.
The mixture was stirred at r©©m temperature f©r ©ne h©ur and
50 ml ©f water was added t© the ©range-red mixture. A few
milliliters of this orange-red mixture was taken and acidi
fied; the mixture changed into dark gray at ©nee. Therefere
n© acid was added t© the mixture. The flask centents were
evap©rated under reduced pressure at r©©m temperature. A red
oily layer separated from aqueous layer after the tetrahydro
furan was evaporated. It was extracted with benzene until
benzene was no longer col©red. The benzene extract was dried
over anhydrous sodium sulfate,
•Rie residual aqueous portion was c©©led in am ice bath
and acidified with hydr©chl©ric acid, A light yellcw am©r-
phous solid (A) precipitated out. This was filtered and wash
ed with ice-cold water. After being kept inside a vacuum
desiccator overnight, the solid chamged into dark tar smelling
54
of 1-nitronapIithalene. The tar was diss©lved in benzene and
passed thr©ugh an alumina c©lumn ©f 1 cm diameter and 25 cm
length. The first p©rtion ©f benzene elutien was red c©l©red
which was followed by a dark soluti©n. The red s©luti©n,
after evaporation gave a red solid which smelled of naphtha
lene. However, by the subsequent recrystallizatlon fr©m
aqueous-alcohol, ©nly 0,32 g ©f l-nltr©naphthalene was re
covered, m,p, 55-58°,
The benzene soluti©n, after rem©val ©f s©dium sulfate,
was passed thr©ugh am alumina c©lumn, 2 cm in diameter and
30 cm in length. The benzene eluted, red s©luti©n gave ©nly
a red solid which smelled ©f 1-naphthylamlne after evap©ra-
tion. It was washed with acid and the acid solutl©n was c©m-
bined with the original acidic s©luti©n (B) remaining after
the filtratl©n ©f (A). The brewnish residue, after acid
washings, gave only tar by sublimation.
The acidic soluti©n (B) was made alkaline and steam
distilled. Prom the distillate, 1.10 g (12.9^ yield) ©f
1-naphthylamine hydr©chl©ride was ©btained. The free amine
obtained by neutralization melted at 47-49 .
The ethamolic washing ©f the column after elution gave
only a tar-like substance after evap©ratl©n. 1-Nitr©naphtha
lene, 0.07 g, was c©llected fr©m sublimati©n ©f the tar.
The total recovery of 1-nitronaphthalene was O.39 g (^,1%),
NN-LBH-III. 1-Nltronaphthalene, 17.3 g (O.l mole),
in 35 ml of tetrahydrofuran was added to 35 ml of a tetra-
55
hydrofuran s©lutl©n of 1,77 g (0.08I mole) of lithium boro
hydrlde immersed in an ice bath. After 3,5 hours ©f stir
ring at r©©m temperature, the red mixture was ceoled to -50°,
amd 150 g of dry ice powder was added under stirring. The
mixture was kept at ro©m temperature ©vernight. Water was
added and the tetrahydrefuran was evaperated ©ff at r©©m
temperature under reduced pressure. After the mixture was
free fr©m the tetrahydr©furan, it was extracted with ether.
The ether extract (A) was washed with 10^ hydr©chl©ric acid
(B).
Four grams of white crystalline pr©duct separated fr©m
the aque©us portion after chilling. This was proved to be
inorganic lithium salt by flame test and qualitative analysis.
The filtrate, after removal ©f the salt, was acidified with
c©ncentrated hydr©chl©ric acid. A light yellcw s©lid was
precipitated ©ut. This was similar to (A) in NN-LBH-II, and
decomposed into dark tar in a vacuum desiccator. This tar,
weighing 0,5 g, dissolved in sodium hydroxide giving a faint
smell of ammonia. No precipitate appeared on acidification
after treatment with charcoal. The filtrate from the light
yellow solid was extracted with ether (C) and the aqueous
portion was discarded,
A dark tar, weighing O.O8 g, having a phenolic smell
remained after evap©rati©n ©f the ether extract (C), N©
solid obtained after the treatment with charcoal in ethanol.
56
The acid washing (B) was made alkaline and steaim dis
tilled. Further treatment of distillate gave 2,03 6 (11.3^
yield) of 1-naphthylamine hydr©chl©ride, The free amine
liberated by s©dium hydroxide melted at 46-48°,
The dark tar which was ©btained fr©m the evap©ration
of the ether extract (A) gave 4,24 g (2h.6% recovery) ©f 1-
nitronaphthalene, m,p. 56,5-58°.
Reduction with Diborane
NN-DB-I. Sodium bor©hydride, 2,22 g (O.O56 m©le),
in 100 ml of diglyme was added dropwise t© 11,1 g (0,078
m©le) of boron trifluorlde etherate in an hour. The diborane
thus fonned was swept with a current of dry nitrogen into
5 g (0,029 mole) of 1-nitronaphthalene in I50 ml of tetra
hydrofuran in another flask. As no color change was observed,
m©re diborane^ liberated fr©m 6.66 g (0,17 m©le) ©f s©dlum
bor©hydride and 30 g (0,24 m©le) of bor©n triflu©ride ether
ate was bubbled int© the solution of 1-nitronaphthalene,
Acetone was used to trap the diborane issuing from the re
action flask. When all of the sodium b©r©hydride had been
added and gas evoluti©n had ceased, ethan©l was added t© the
tetraUtiydrofviran s©luti©n, Vig©rous ev©lution ©f gas was ob
served. The solution was evaporated on a steam bath until a
precipitate appeared. The mixture was then cooled and fil
tered. The solid was washed with dilute hydrochl©ric acid.
The dark purplish solid weighed 5.84 g. By sublimation.
57
4.64 g (935 ) of 1-nltronaphthalene was recovered, m.p. 58-/- o
6o .
NN-DB-II. NN-DB-I was repeated with the addition of
one graim ©f zinc dust t© the s©luti©n ©f l-nitr©naphthalene
The same treatment gave 4.97 g (99.4 ^ reccvery) of 1-nitronaphthalene, m.p. 58.5-60 ,
Preparation ©f Naphthyl Lithium and lis Reaction with Nitr©us Oxide
NL-NO-I. Thirty-five milliliters ©f anhydrous ether
was placed in a 250 ml three-neck flask equipped with a me
chanical stirrer, a reflux condenser, amd a dropping funnel
and gas inlet amd outlet tubes. The flask was flushed with
dry nitrogen. Lithium shavings, 1,50 g (p, 2l6 mole), was
added at once and the mixture was stirred, l-Brom©naphtha-
lene, 20.7 g (O.l m©le), in 35 ml ©f anhydr©us ether was
added dropwise in 2,5 hours. The col©r ©f mixture changed
into dark purple. At the end of reacti©n 50 ml ©f anhydr©us
ether was added and the flask was Immersed in ice-s©dium
chloride mixture.
Nitrous oxide gas was bubbled slowly through the solu
tion for one hour. The c©l©r of the mixture became darker.
Twenty milliliters of methanol followed by 80 ml of water
was added. The ether was evaporated at r©©m temperature.
The mixture smelled strongly of naphthalene. The alkaline
solutl©n was decanted amd the residual dark gummy substance
58
was washed with dilute s©dlum hydroxide amd water. After
suspending in dilute sulfuric acid, it was steam distilled.
Crude naphthalene, 4.9 g (38.3^ yield) was obtained; m.p.
80-82° after recrystallizatlon from ethanol.
The residue from steam distillation was a pitch-like
black substance which weighed 10,68 g. Sublimation under
reduced pressure yielded n© azonaphthalene but a little red
oil smelling of naphthalene.
NL-NO-II. 2-Naphthyl lithium was prepared as in NL-
NO-I using 6.5 g (0,94 mole) of lithium and 8 g (0.039 mole)
of 2-bromonaphthalene.
Nitrous oxide was passed through the solution of 2-
naphthyl lithium for 4 hours while the flask was immersed
in ice-sodium chloride mixture and one hour at ro©m tempera
ture. Twenty milliliters ©f methanel foll©wed by 80 ml of
water was added and the mixture was stirred for two hours
until no more gas evolved. The organic layer was separated
amd washed with porti©ns ©f water (A).
The ©rganic s©luti©n was evap©rated t© dryness after
washing with dilute sulfuric acid amd water. The residue
was sublimed at 80-90°, Naphthalene, weighing 1,52 g (30.7^
yield), was obtained, m.p, 78-80 .
The sublimation was continued in vacuo and the tem
perature was raised to I6O-I7O , A red substance, weighing
1,16 g, was obtained. By the treatment with charcoal and
recrystallizatlon from benzene, colorless flakes with faint
59
blue fluorescence was ©btained, m.p. 184-186.5° {23,6% yield)
The melting p©int ©f 2,2»-dinaphthyl is 187-188° (48),
The basic s©luti©n (A) was acidified with dilute sul
furic acid and the precipitate which smelled phen©l-like was
filtered, Dec©l©rizati©n and recrystallizaticn fr©m aque©us-
alcohol gave 26,8 mg ©f 2-naphth©l, m,p, 120-122°, The melt
ing p©int ©f 2-naphth©l is 123° (^9).
Infra-Red Abs©rpti©n Spectrum ©f the C©mp©und (A)> DNB-KBH-I
Infra-red abs©rpti©n spectrum was ©btained ©n a Perkin-
Elmer Single Beam Infrared Spectrcmeter with D©uble Pass
Itonochrometer, Model 112, using a pressed tablet ©f 400 mg
potassium bromide mixed with ©ne milligram ©f the sample.
Table IV indicates the peaks, their relative intensity and
structural assignment (49) (50) ©f the spectrum reproduced
in Figure 1.
60
TABLE IV
INFRA-RED ABSORPTION SPECTRUM OF THE COMPOUND (A), DNB-KBH-I
Wave length (microns) Assignment
5.2 (w 6.22(m 6 .3 ( s 6.57(m 6.65(m 6.86(m 7.08(m 7.17(m 7.^6(m 7 .66(s 7.91(w 8.04(m 8.30(s 8,50(w 8.60(w 8 ,79(s 8,85(s 9 . 1 l ( s 9.6l(m 9 .98(s
10,30 10.42 10.89(m 11.03{m 11.64(s 12.9l(ni 13.17(w
w w
a ,b a ,b a a ,b a ,b a ,b
b a a ,b
b a a ,b
a ,b a ,b a ,b
a
a ,b
b
a
C- ' C stretching, phenyl ring vibration, N-H deformati©n. conjugated phenyl ring vibration, NO2 stretching, phenyl ring vibration, N»N stretching. N=N stretching. C-H bending. NO2 stretching. -C-N= bending, not assigned, not assigned, C-H rocking. C-H r©eking, C-H r©cking. -C-N« vibrati©n, C-H wagging. C-H r©eking. C-H r©cking. C-H bending. C-H def©rmati©n. C^^^ stretching. -C-N« vibratl©n. C-H wagging, p-substituted ring vibrati©n, p-substituted ring twisting, substituted ring twisting.
a. Peaks in the spectrum of 4-phenylazo-4»-(p-nitro-phenylaz©)-az©benzene (50),
b. Peaks in the spectrum ©f 4-phenylaz©-4»-(p-amin© phenylaz©)-az©benzene (50).
61
FIGURE I. INFRA-RED SPECTRUM OF THE COMPOUND (A), DNB-KBH-I
COMPOUND (A), DNB-KBH-I
BACKGROUND
62
Discussi©n ©f Results
At the ©utset ©f the research pr©Ject described in
the thesis, the aim was t© use metal hydride cemplexes f©r
the reductive ccupling ©f 1-nitr©naphthalene.
The result ©f Br©wn and Nystr©m (3), the reductive
c©upling ©f nitrobenzene to az©benzene with lithium aluminum
hydride, was c©nflrmed. With l-nltr©naphthalene, the pr©-
ducts were mainly an intractable dark brewn s©lid with a
small am©unt ©f 1-naphthylamine; and, ©ccasi©nally an ex
tremely small ameunt ©f l,l*-az©naphthalene. If the f©rma-
ti©n ©f 1-naphthylamine f©ll©wed the same stepwise c©urse
thr©ugh nltr©s©-, hydr©xylamln©-, az©xy-, az©- aind hydraz©
c©mpound as sh©wn in the electrelytic reductien ©f nitr©ben-
zene in an alkaline medium (l), l,l*-az©naphthalene should
be reduced to 1-naphthylamine with lithium aluminum hydride.
The bright red c©l©rati©n ©bserved during the c©urse ©f m©st
©f the reducti©ns and its subsequent changing int© dark
br©wn was th©ught t© be an indicati©n ©f the f©rmatl©n ©f
the az© c©mp©und as an intermediate which was transf©rmed
int© tar ©r the amine by the further treatment. Repeated
experiments with l,l*-az©naphthalene sh©wed this supp©siti©n
t© be false.
While l-nltr©naphthalene was scarcely reductlvely
ccupled to form the azonaphthalene, a substituted nltronaph
thalene, 5-br©m©-l-nitr©naphthalene was reductlvely coupled
63
to give what is believed t© be a mixture of 5,5•-dibrom©-
1,1'-azonaphthalene and 5,5»-dlbr©m©-l,l'-az©xynaphthalene.
•niis result was in accordance with the results of Wacker (8).
With sodium-, potassium- aind lithium b©r©hydrlde, n©
azo compound was isolated. Nevertheless the bright-red col©r-
ati©n was always ©bserved in the ceurse ©f reduction. In all
of the experiments with b©r©hydrides a small am©unt ©f naph
thalene was formed. With lithium aluminiam hydride, naphtha
lene was isolated only from the inverse addition method while
its existence was detected in other cases only by ©d©r. The
course of the hydrogenolysis is not clear. The naphthalene
could not have been formed from first-formed naphthylamine,
since experiments with 1-naphthylamine led only to the re
covery of the naphthylamine. The fact that the light colored
amorph©us s©lid is©lated fr©m the acidic decompositi©n mix
ture of the lithium b©r©hydride reductions changed into a
dark tar smelling of naphthalene might be an indication that
naphthalene was derived from the decomp©8ition of a metal
hydride organo-complex. Such a c©mplex, if present, did not
have a naphthyl lithium bond, since no naphthoic acid was
isolated from NN-LBH-III in which dry-ice powder was added
to the reaction mixture. It is possible that attack of the
reducing agents at the pelar C-N bond leads to the formatl©n
©f naphthalene, whereas attack which occurs more frequently
at the polar N-0 bond leads to the formation ©f az©- or
aminonaphthalene. There has been no direct evidence for this
64
speculation, however. The nitro group hydrogen©lyzed was,
perhaps, reduced t© amm©nia as the od©r ©f amm©nia was de
tected in NN-LBH-III, when the tar derived fr©m the am©rphous
light col©red solid was treated with sodium hydroxide.
The identity of the yellow comp©und ©btained in small
yield in NN-NBH-I is net kn©wn yet. It was m©st likely f©rmed
by the effect ©f high temperature which was accidentally at
tained by the additi©n ©f s©lid l-nitr©naphthalene t© the
b©rohydride suspensien.
In c©ntrast with an early established fact that the
nitr© group is resistant to attack by potassiiim b©rohydride,
nitr©benzene was reduced to azoxybenzene in 60-70$ yield ©n
pr©l©nged heating in alcoh©lic s©lutl©n.
Pr©m the fact that nitrcbenzene was reduced with b©th
s©dium and p©tassium b©r©hydride t© az©xybenzene (21) and
p-dinitr©benzene was reduced with sedium b©r©hydrlde to p,p'-
diaminoazoxybenzene (DNB-NBH), a simple azoxy c©mp©und was
expected t© be fermed from the reduction of p-dinitrobenzene
with potassium borohydrlde. However, the main product, the
compound (A) ©f DNB-KBH-I, appeared t© be a high molecular
weight compound; it did not have a melting point and was ex
tremely insoluble in solvents. Because it gave p-phenylene-
diamine on reduction, it was believed t© be a p©lyaz© c©m-
pound. The compoiind C24^ig-^7^2 ^^^^ ^^® structure
65
0 — ^ — 0 ^ —
and the c©mp©und Cgi^H^^N^O^, with the structure
have compositl©ns agreeing with the analysis ©f the c©mp©und
(A). Nevertheless the similarities in c©mp©siti©n are n©t
c©nclusive evidence. In particular, the tw© az©xy groups
are rather arbitrary. The infra-red spectrum ©f the c©mp©und
(A) resembles that ©f the 4-phenylaz©-4'-(p-nitr©phenylaz©)-
azebenzene, rep©rted by Uen© (50), H©wever there are seme
peaks in the spectrum ©f (A) which are net in the latter,
and Uene's spectrum has seme peaks, 6.4, 7,0, 7.3* 7.6, 9,37,
10.03, and 12,76 mlcrens, which are missing fr©m the former.
The spectrum of the c©mp©und (A) als© has s©me resemblance
to that of the 4-phenylaz©-4»-(p-aminophenylaz©)-azobenzene
(50), However, of the two peaks assigned for amino group in
the latter, 6.22 microns for N-H deformati©n and 7.85 micr©ns
f©r C-N stretching ©f C-NHg b©nd, ©nly the 6.22 mlcrens ap
pears in the former. Also, 6.22 microns peak is not unique
for N-H b©nd. These facts lead to the obscuration of the
existence ©f amin© group in the c©mp©und (A),
66
The extent ©f reductive ceupling ©f p-dinitr©benzene
depends ©n the nature ©f the selvents and the temperature.
With N,N-dimethylaniline as the selvent, the reductive c©up-
ling ©f p-dinitr©benzene with petassium b©r©hydride yielded
n© c©mp©xjind resembling the cempound (A) ©f DNB-KBH-I, but
4,4'-dinitr©az©benzene.
Besides the c©mp©und (A), p-nitr©phenet©le was als©
f©rmed in the reductien ©f p-dinitr©benzene with petassium
borohydrlde in ethanol. However, this formation was proved
to be nucleephllic substituticn by the ethexy group as the
same comp©und was als© ©btained in the absence ©f the reduc
ing agent. The reactien apparently ©ccurred as described
by Antener (33).
As reperted with nitrebenzene (29), the nitr© gr©up
in l-nitr©naphthalene was resistant t© the action of diborane
at ro©m temperature,
nie results ©f the reactlen between nitreus ©xide and
naphthyl lithium differed fr©m the result given previeusly
(30). N© azonaphthalene was isolated but dinaphthyl was ob
tained in addition to naphthalene.
CHAPTER IV
CONCLUSION
1, 1,1'-Azonaphthalene was obtained in 5.3^ yield
from the reduction of 1-nitronaphthalene with only lithium
aliiminum hydride. With b©r©hydrides n© az ©naphthalene was
iselated,
2, Up t© 205 1-naphthylamine was always ©btained fr©m
the reaction of 1-nitronaphthalene with all the hydride com
plexes. The naphthylamine is not f©rmed fr©m first-f©rmed
az©naphthalene.
3, Some hydrogenelytic cleavage ©f the nitr© gr©up
in l-nitr©naphthalene ©ccurred with every hydride cemplex,
4, Nitrebenzene was reduced with petassium b©r©hydride
to give azoxybenzene in 6l% yield.
5, The product from p-dinitrobenzene depends on the
reducing agent, solvent and temperature. 4,4»-Diamin©az©xy-
benzene, 4,4'-dinitr©az©benzene and a compound resembling a
poly azo comp©und were fermed in different cases. p-Nltro-
phenetele, a substitutien product, was also Isolated when
ethanol was used as the solvent.
67
68
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n
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70
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(42) Private c©mmunicati©n, Mr. R. L, Snell.
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