The benzilic acid rearrangement; the function of the catalyst

Item Type text; Thesis-Reproduction (electronic)

Authors Sprovieri, Salvatore Rudolph, 1931-

Publisher The University of Arizona.

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THE BENZ1LIC ACID REARRANGEMENT

THE FUNCTION OF THE CATALYST

by

S a lv a to r e R. S p r o v ie r i

A T h esis

su b m itted to th e f a c u l t y o f the

Department o f C hem istry

in p a r t ia l f u l f i l l m e n t o f th e req u irem en ts fo r th e degree

MASTER OF SCIENCE

in th e G raduate C o lle g e , U n iv e r s ity o f A rizona

195k

Approved:D ir e c to r o f T heses

T h is .t lie sits has b een su b m itted in p a r t i a l f u l f i l l m e n t

o f req u irem en ts f o r an advanced degree a t th e U n iv e r s ity

o f A rizon a and- i s d e p o s ite d , in th e L ib ra ry to be made ' ;

a v a i la b le t o borrow ers under r u le s o f th e L ib r a r y 0

B r ie f q u o ta tio n s from t h i s t h e s i s are a llo w a b le w ith o u t

s p e c ia l p erm issio n ;, p ro v id ed th a t a c cu ra te acknow ledg­

ment o f sou rce i s made, R eq u ests f o r p e r m is s io n fo r

ex ten d ed q u o ta t io n from or r e p r o d u c tio n o f t h i s manu- •

s c r ip t i n Whole or in . part-, may be gran ted by th e head

o f th e m ajor departm ent or th e dean o f th e: Graduate.

C o lle g e when in t h e ir judgm en t:the p rop osed u se o f th e

m a te r ia l i s in th e i n t e r e s t s -of • s c h o la r s h ip 0 In a l l

o th e r in s t a n c e s , however^ p e r m iss io n must be o b ta in e d

from th e auth or 0

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The author H isjaes to iexpiPess h i s thanks to Dr0 A« Ba

K e l le y .f o r h i s c o n s i s t en t as s i s t a n c e ■a n d 'g u id an ce d u r in g ::

t h i s e n t i r e research ^

'Timm OP CONTENTS ; :

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M a te r ia ls • ' . > : . ' /V:- > • .:v 12'i

. Apparatus , ::v . 7 • ■' ' : 12

B e n z i l io a c id rearrangem ent :: r .. 12

P o ta ssiu m h yd rox id e c a t a l y s i s 13

Sodium amide .c a t a ly s i s ■ " : 13

P r e p a r a tio n o f sodium a n i l i d e l );

C a ta ly s is by sodium anilm de 13

- p r e p a r a tio n o f sodium E ^ m eth y la n ilid e 15

C a ta ly s is by sodium H -m e th y la n ilid e . I...

Ao D ecom p osition w ith w ater 15

, B.o D ecom p b sltion -with dry EC1 15

P r e p a r a tio n o f sodium ph en oxid e ■ 16

C a ta ly s is by sodium p h en oxide . ■ - 16

S uzpmui y © © 0 © © © © © © 0 © © © © © © © © © © .©. © © © © © © © © © © © © © © © © ©. © ©. © ©. © © © © © © © l,* -

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INTRODUCTION

I t has been m a in ta in ed th a t th e rearrangem ent o f b e n z i l

to b e n z i l i c a c id i s s p e c i f i c a l l y c a ta ly z e d by h yd rox id e io n ,

b u t n ot by b a se s in g e n e r a l ( 1 ) . K in e t ic s t u d ie s p ro v id e v e r y

s a t i s f a c t o r y e v id e n c e fo r th e p a r t ic ip a t io n o f h yd roxid e io n

in th e b e n z i l i c a c id rearrangem ent ( 2 ) . These s tu d ie s have

shown th a t th e r a te o f r e a c t io n i s p r o p o r t io n a l to th e con cen ­

t r a t io n o f b e n z i l and a ls o to th a t o f h yd rox id e io n , but i s

in d ep en dent o f such s tr o n g B ro n sted (or L ew is) b a se s as

phenoxide io n and o - ch lo ro p h en o x id e io n .

In th e l i g h t o f th e k in e t i c r e s u l t s th e a c c e p te d mechanism

fo r th e rearrangem ent o f b e n z i l to b e n z i l i c a c id u s in g

p o ta ssiu m h yd rox id e as the b a s ic c a t a l y s t i s i l l u s t r a t e d and

e x p la in e d by Wheland (1) as f o l lo w s :

o o ~o o - o o -

11 The p o s tu la te d in te r m e d ia te which i s presumed to undergo the a c tu a l rearrangem ent i s h ere an an ion form ed by th e a d d it io n o f a h yd rox id e io n to a m o lecu le o f b e n z i l . T h is io n d o u b t le s s r e s ­o n a te s betw een / t w o /s t r u c t u r e s

OH

-0 0 ~

- o o - o o

2

o f w hich th e seco n d , and presum ably l e s s im p ort­a n t , one has th e r e q u ir e d open s e x t e t . The fu n c ­t io n o f th e b a se in making th e rearrangem ent o c ­cur sh ou ld now be app arent; / t h e f i r s t / s t r u c tu r e , as a r e s u l t o f i t s l e s s u n fa v o ra b le d i s t r ib u t io n o f e l e c t r i c ch a rg e , must make a la r g e r c o n tr ib u ­t io n to the s t a t e o f th e n e g a t iv e io n th an th e analogou s s tr u c tu r e

makes to th a t o f th e n e u tr a l b e n z i l m o le c u le . ,«The rearrangem ent i s th e r e fo r e c a ta ly z e d s p e c i f i ­c a l l y by h yd rox id e io n , bu t n o t by b a se s in g en er­a l . T h is c o n c lu s io n shows th a t th e an ion r e s o n a t ­in g / a s showr^Z must b e an in te r m e d ia te in th e r e a c t i o n .”

A p p aren tly th e b ase i s n e c e s s a r y to n e u t r a l iz e th e p o s ­

i t i v e charge on one carbon to a llo w reson an ce o f th e o th e r

ca rb o n y l group w ith o u t v i o la t i n g th e a d ja c en t charge r u le .

However, phen oxide io n would do t h i s as w e l l as th e h yd rox id e

io n , and th e r e fo r e th e fu n c t io n o f th e base i s n o t a d e q u a te ly

e x p la in e d .

C o n sid e r a tio n o f th e s p e c i f i c c r y s t a l l i n e s tr u c tu r e o f

b e n z i l and th e r e l a t i v e p o s i t io n s o f th e groups w ith in th e

m o lecu le s u g g e s ts a m o d if ic a t io n o f Wheland* s m echanism . I t

has been found th rou gh th e v a lu e s o f th e d ip o le moments in

v a r io u s s o lv e n t s , in c lu d in g b en zen e , th a t b e n z i l may have a

skew c o n f ig u r a t io n in w hich th e two C^Hg-C=0 u n i t s l i e in

p la n e s w hich are n e a r ly m u tu a lly p e r p e n d ic u la r ( 3 ) .

O O"

between planes * 90-100°

F urtherm ore, an a n a ly s is o f th e s tr u c tu r e o f c r y s t a l l in e b en -

z i l , b ased on com p lete X -ray m easurem ents, h as e lim in a te d th e

s im p ler m o lecu la r s tr u c tu r e s and has shown th a t th e b e n z i l

m o lecu le must be o f such a skew ty p e ( I 4 - ) •

W ith t h i s e v id e n c e , and a r e c o g n it io n o f th e f a c t th a t

th e h yd rox id e io n m ight form an in t e r n a l hydrogen bond, Wheland*

mechanism can be r e w r it t e n u s in g s t r u c tu r e s in w hich hydrogen

bonding i s shown.

Through th e u se o f F is h e r -T a y lo r -H ir s c h fe ld e r atom m od els,

i t can be seen th a t th e skew s tr u c tu r e fo r b e n z i l b r in g s th e

h y d ro x y l hydrogen atom in c lo s e p r o x im ity to th e rem ain ing

carb on y l oxygen i f th e i n i t i a l com plex i s form ed by an

ap p rox im ate ly rearw ard a t ta c k on one carb on y l group to g iv e

OH"

th e u su a l t e t r ahe dr a l l y d ir e c te d bonds on th e carbon under

a t ta c k . Thus th e s tr u c tu r e r e a d i ly a llo w s fo r in t e r n a l h y­

drogen bond form at io n o'- S in ce phen oxide io n w i l l n o t cau se

the. rearrangem ent to o c c u r , i t i s p o s tu la te d th a t th e r e ­

quirem ent f o r c a t a l y s i s i s a b ase w hich can form an in t e r n ­

a l hydrogen b r id g e when added to th e ben z11 m o le c u le »■ T his

view i s su p p orted by th e r e p o r ts th a t b e n z ila m id e i s among

th e p ro d u cts i s o l a t e d from th e trea tm en t o f b e n z i l w ith a l ­

c o h o l ic ammonia ( 5 ) 3. and th a t sodium amide in to lu e n e g iv e s

"a good y ie ld " o f b e n z i l i c a c id from b e n z i l ( 6 } 0

The aim o f t h i s r e se a r c h was to t e s t th e assum p tion

th a t th e req uirem en t fo r c a t a l y s i s i s a b ase w hich can form

a n - in te r n a l hydrogen b r id g e when added to th e b e n z i l m ole­

c u le , Thus b e n z i l was t r e a te d w ith v a r io u s b a s e s i n an

a p r o t ic s o lv e n t , , and th e p rod u ct I n v e s t ig a te d f o r t h e ;p r e s ­

ence o f b e n z i l i c a c id . A ccord in g to th e p o s t u la t e d mechan­

ism o f th e r e a c t io n , a base such as sodium a n i l i d e sh ou ld

cau se rearran gem en t, w h ile sodium N -m e th y la n llid e sh ou ld n o t

5

DISCUSSION

I t was f i r s t n e c e s s a r y to d e term in e w hether th e r e ­

arrangem ent w i l l p roceed in an a p r o t ic s o lv e n t such as b en ­

zene and to e s t a b l i s h optimum c o n d it io n s fo r th e r e a c t io n

w ith sodium am ide. I t was found th a t a 97% y i e l d o f b e n z i l i c

a c id c o u ld be o b ta in e d u s in g f i n e l y powdered p o ta ss iu m hydrox­

id e in benzene a t th e r e f lu x tem p era tu re . W ith sodium amide

in r e f lu x in g b en zen e , v a r y in g th e r e a c t io n tim e gave a maximum

y i e l d o f 6l% fo r a th r e e hour r e a c t io n . E ith e r lo n g e r or

sh o r te r r e a c t io n tim es gave sm a lle r amounts o f p ro d u ct. A l l

su bseq uent r e a c t io n s u s in g sodium a n i l id e s were run at th e

c o n d it io n s w hich were found to be optimum fo r th e sodium amide

r e a c t io n . The produ ct o b ta in ed from th e rearrangem ent w ith

th e amide io n m elted a t l5 0 ° and d is s o lv e d in c o n c e n tr a te d

s u l f u r ic a c id to g iv e a deep red c o lo r a t io n , b o th c h a r a c te r ­

i s t i c o f b e n z i l i c a c id .

A p plying th e p o s tu la te d mechanism fo r t h i s rearrangem ent

to th e c a se o f th e amide:

T his mechanism im p lie s th a t th e amide o f b e n z i l i c a c id

sh ou ld be th e p ro d u ct. However, a q u a l i t a t iv e t e s t fo r

n itr o g e n on th e i s o l a t e d m a te r ia l was n e g a t iv e . The prod u ct

was o b ta in e d by e x tr a c t io n in to w a te r , th e e x c e s s rea g en t

h y d r o ly z in g to form a s t r o n g ly b a s ic s o lu t io n . The product

was p r e c ip i t a t e d by n e u t r a l iz a t io n o f th e aqueous e x tr a c t

w ith s u l f u r ic a c id . During th e s e i s o l a t i o n s t e p s i t i s p o s ­

s i b l e th a t th e amide h y d r o liz e d to th e f r e e a c id . A ttem pts

to i s o l a t e th e amide o f b e n z i l i c a c id by c a r e fu l h y d r o ly s is

and n e u t r a l iz a t io n a t low tem perature were u n s u c c e s s fu l and

r e s u l t e d o n ly in a d ecrea sed y i e l d o f th e b e n z i l i c a c id .

I f hydrogen bond fo rm a tio n i s th e c r i t e r i o n , sodium

a n i l id e sh ou ld a ls o c a ta ly z e th e rearrangem ent a cco rd in g to

th e fo l lo w in g mechanism:

The p r e d ic t io n proved to be c o r r e c t in th a t a 62$ y i e l d

o f p r o d u ct, a g a in th e a c id r a th e r than th e a n i l i d e , was ob­

ta in e d . The y i e l d o f b e n z i l i c a c id was th e same w hether

sodium a n i l id e or sodium amide was u sed .

II

The mechanism was th en a tta c k e d from th e n e g a t iv e s id e .

A c a t a l y s t , sodium N -m e th y la n il id e , was s e l e c t e d w hich

sh o u ld n ot b r in g about th e rearran gem ent, s in c e no hydrogen

atom i s a v a i la b le f o r hydrogen b on d in g ,

*<y <b Ov . k-ch ,

, > < > — * > ■ < -« ? .

However, a 1 2.% y i e l d o f b e n z i l i c a c id was i s o l a t e d .

This b e n z i l i c a c id co u ld p o s s ib ly have a r is e n during

th e h y d r o ly s is and i s o l a t i o n s t e p s , th e h yd rox id e io n form ed

by th e d eco m p o sitio n o f th e b e n z i l - b a s e com plex a c tu a l ly

c a u sin g th e rearran gem ent,

♦ “ .■> — - - « • -

S in ce a c a se was known in th e l i t e r a t u r e (2 ) in w hich

a b a se , th e p h en oxide io n , f a i l e d to g iv e b e n z i l i c a c id ,

t h i s b a se was u sed to t e s t the a p p l i c a b i l i t y o f th e i s o l a ­

t io n p roced u re .

A r e a c t io n w ith sodium p h en oxide was run a n a lo g o u s ly

to th a t w ith sodium N -m e th y la n il id e . H y d r o ly s is o f the

b e n z il-p h e n o x id e com plex and a c i d i f i c a t i o n w ith d i lu t e s u l ­

f u r ic a c id produced a c lo u d y s o lu t io n , but no f i l t e r a b l e

p r e c ip i t a t e co u ld b e o b ta in e d . I t was con clu d ed th a t no s i g ­

n i f i c a n t amount o f rearrangem ent had o ccu rred .

A nother case , has' been r e p o r te d .in w hich a b e n z i l -b a s e

com plex can be decompbsed by w ater w ith o u t rearran gem en t0

Lachraan (7 ) found th a t ;sodlum':e th d x y b e n z ll decom posed "in ­

s t a n t ly ,and q u a n t i t a t iv e ly ” ■when added to -w a ter : to g iv e b en -

z i l j sodium h y d ro x id e , and e th a h q l0 . • how ever, t h i s •o b s e r v e - ' .

t i o n was made 'w ith the' dry .cbimplex, w ith o u t e x c e s s sodium :

ethoxi:de,0;; ':/Wheh:: the; com plex was : a llo w ed to sta n d in the, s o l ­

v en t f o r ;fou r , d a y s .w ith 20% q f w a te r . p r e s e n t , an 80% y ie ld " .

o f b e n z i l l c :a c id was ;o b ta in e d , • Even in th e ab sen ce o f w a te r ,

from 2 t o . 5%- o f ■ b en zilic a c id was i s o l a t e d , e i t h e r by a t ta c k

On th e s o lv e n t , or by fo rm a tio n du rin g th e i s o l a t i o n p r o - '

; J ;The d i s p a r it y betw een th e o b s e r v a t io n s f o r M-methyl™ i -

a n ll id b : and phenoxlde. may; be .due to th e f a c t th a t ph en oxide

i s a much Weaker b a se th an th e a n i l i d e , and th u s g iv e s a

low er c o n c e n tr a t io n o f h yd rox id e io n in th e h y d r o ly s is me­

dium, Lachman8 s low y i e l d o f b e n z i l i c a c id upon deeom posi-

t i o n o f th e e th o x id e com plex may th e n be due t o o th e r f a c ­

t o r s , s in c e e th o x id e io n has a b ase s tr e n g th more n e a r ly

com parable t o th a t o f th e a n i l id e <>' Such f a c t o r s co u ld a r is e

from d if f e r e n c e s I n th e h y d r o ly s is p ro ced u re , or from th e

p r e sen ce o f e x c e s s b ase a lo n g w ith th e com plex i n th e p r e s - :

ent,.worka" .Thus, a lth o u g h th e b e n z i l -b a s e com plex' may, d e- •

compose as shoW n,to produce h yd rox id e io n , i t i s p rob ab le :

t h a t : t h e e x c e ss sodium E -m e th y la n ilid e w i l l g iv e a r e l a t i v e -

l y M gh, c o n c e n tr a t io n o f h yd rox id e io n even b e fo r e th e com­

p le x has d eco m p o sed .a p p rec ia b ly = S in ce a tw o - fo ld e x c e ss o f

b ase to b e n z i l was h s e d , th e f i n a l o o n e e n tr a t io n o f hydrox­

id e io n b e fo r e a c i d i f i c a t i o n w i l l a lso: be. tw ic e th e con cen ­

t r a t io n o f th e b e n z i l o- : ’ v ‘; : /

I f th e rearrahgem ent were ta k in g p la c e d n rln g th e i s o - . ;

l a t i o n p roced u rej th e n b e n z i l l c a c i d , . r a th e r th a n th e am ide,

w ould , o f c o u r s e , be form ed d ir e c t ly ^ F a ilu r e to o b ta in a ;• •

h i t r o geh - c e n t a ih in g pro due t w ould th e n b e 'e x p la ih e d o : '

A method o f d eco m p o sitio n o f th e b e n z i l - b a s e complex. ■ .

was th e n sou ght in w hich th e u se o f w ater was a v o id ed w h ile

a h ig h c o n c e n tr a t io n o f base was p r e se n t 0 . G-aseous h y d ro g en .

c h lo r id e - was u se d t o remove th e -b a s e b e fo r e th e e x tr a c t io n

o f w ater - s o lu b le s 'a lts a : - , ■ - ' • . .

The r e a c t io n , w ith sodium H -m eth y la n ilid e . was a g a in p e r -

• form ed, and dry hydrogen c h lo r id e was s lo w ly added to th e

. su sp e n s io n o f th e com plex t o b e n z e n e , u n t i l e x c e s s a c id wasd

. p resen to Upon e x tr a c t io n and i s o l a t i o n o f th e product:, a

10^ y i e l d o f b e n z i l l c a c id was ob ta in ed o ;

A lthpugh in t h i s ca se o n ly a sm a ll amount o f rea rra n g e ­

ment had o c c u r r e d , i t i s ■necessary to ’ 'co n sid er how th e r e -

a c t io n m ight have p roceed ed t o ; th a t e x te n t i n th e '’absence*8

o f th e p o s tu la te d c o n d it io n s f o r rearrangem ent- - 1he fo r m a -,

t i o n o f an in t e r n a l hydrogen'bohd i n th e com plex0 ' /

;' . V I t seems u n l ik e ly th a t a lO^ y i e l d o f b e n z i l l c a c id ' '■

10

c o u ld be found i f th e r ea r ra n g in g took p la c e o n ly du rin g

th e e x tr a c t io n o f a c id ic p ro d u cts in t o a sodium carb onate

s o lu t io n . However, s in c e i t was n o t known how v ig o r o u s ly

th e dry hydrogen c h lo r id e would r e a c t w ith th e sodium

N -m e th y la n ilid e and th e b e n z i l - b a s e com plex in b en zen e ,

th e a c id was added v e r y s lo w ly , o ver a p e r io d o f one hour.

The s a l t was a llo w ed to s e t t l e o u t , and th e m ix tu re s to o d

f o r s ix t e e n hours b e fo r e th e s o l i d s were removed by f i l t r a ­

t i o n . During th a t tim e o f s ta n d in g , much o f th e o r ig i n a l l y

p r e c ip i t a t e d s a l t r e d is s o lv e d . T h is in tr o d u c e s an unknown

f a c t o r in to th e p ro ced u re , fo r no r e a c t io n o f p r e c ip i t a t e d

sodium c h lo r id e or IN -me th y 1 an i 1 i n i urn c h lo r id e w ith b e n z i l

was a n t ic ip a t e d .

A fu r th e r chance fo r rearrangem ent i s th e p o s s i b i l i t y

th a t in th e d e c o m p o sit io n o f th e com plex w ith hydrogen c h lo ­

r id e an in te r m e d ia te i s form ed w hich does n o t im m ed ia te ly

decompose in to b e n z i l and b a s e .

C -C -V + HCI< K ' o .

SLOW

( * , '

h ¥+ ClttAftftANCCMCMT

. From th e form ula o f such, a p o s t u la t e d ;in te r m e d ia te I t

i s s e e n . th a t r o t a t io n about th e c e n t r a l carhon-cariDon bond

w i l l a llo w th e fo rm a tio n o f an in t e r n a l hydrogen bond ju s t

as though a h yd rox id e io n had added onto a m o lecu le , o f a

■ h e n z i l - a h i l d e r iv a t l ir e » , This rearrangem ent o f th e in t e r ­

m ed ia te com plex m ight be m in im ized by adding dry hydrogen

c h lo r id e r a p id ly to th e r e a c t io n m ix tu r e 0 ■

• • Sny one o f th e th r e e f a c t o r s j u s t d is c u s s e d - -r e a r r a n g e

ment du rin g e x tr a c t io n in t o b a s ic , so lu tio n ^ rearrangem ent

d u rin g th e unknown r e a c t io n on standing^, and rearrangem ent

b y slow' d eco m p o sitio n o f th e com plex— co u ld a cco u n t f o r th e

fo rm a tio n o f some b e n z l l i e a c id 0 iL com b in ation o f a l l o f

them c o u ld r e a so n a b ly be e x p e c te d tb give' a 10$. y i e l d o f r e

arranged m a ter ia lb : ' t ' j; .

: . SXPSRiMSUTAIi

M a te r ia ls 0 B e n z il was r e c r y s t a l l i z e d from carbon t e t r a - ' \

e t ilo ^ id s W i t ■ was , foartd to m elt sh a rp ly a t 95 o ' -

hydrous benzene was p rep ared by d ry in g o ver f r e s h ly cu t . :

sodium.o F or each o f th e f o l lo w in g exp erim en ts ,ij,00 ml 0 o f ■

so d iu m -d r ied b en zen e .was d i s t i l l e d g th e fo r e r u n o f 80=90 m l0 ' , :

and a ,r e s id u e o f 1 0 -2 0 m l0 b e in g d is c a r d e d , ' • Sodium amide y : :;

m anufactured by th e Far chan R esearch L a b o ra to r ie s , was used*

The ch lo ro b en sen ej' a n i l in e i and H-methy 1 a n i 1 in e were Eastman

Kodak' m a ter ia ls ; , .which were d i s t i l l e d im m ed ia te ly b e fo re

^ y - y ^ ■

A p p aratu so A l l r e a c t io n s » e x c e p t th o se c a ta ly s e d by h y d ro x -.

id e i o n s w ere c a r r ie d ou t in . a. 500 m l»: round-bottom ^ th r e e - :

heck f l a s k w ith ground g l a s s . j o i n t s . a H ershberg s t i r r e r ,

and a F r ie d r ic h condenser* . T h e .r e a c t io n s in v o lv in g sodium

a n i 11 d e , Sodium N -m e th y la n il id e , and sodium ph en oxid e . re-, .

I h ir e d :th e . use^ d f . a se p a r a to r y .fu n h ei! w ith; preS'sure e c ju a llz— :

in g s id e arm f o r th e p r e p a r a tio n d f .the c a ta ly s t * " ■'

B e n z l l l c acid : rea rra n g em en to The e f f e c t i v e n e s s o f a b ase i n •

: c a ta ly z in g th e b e n z l l l c a c id rearrangem ent was ' t e s te d /o n b en - .

z i l i n b en zen e 's o lu t io n in a l l c a s e s * S e v e ra l r e a c t io n s :

were perform ed w ith p o ta ss iu m h yd rox id e as th e b a s e , i n o r -

: der to dem onstrate th a t as h ig h a y i e l d co u ld be o b ta in ed ■

in . th e hydrocarbon s o lv e n t as i n th e u su a l aqueous mediumy I

A fte r s e v e r a l t r i a l s in w h ic h .v a r io u s r e a c t io n tim es .

i ie r e '• iised g " c o n d it io n s ' were e s t a b l i s h e d fo r a maximum y i e l d

o f h e m l l l c a c id w ith sodium.' am ide. as c a t a l y s t » Those p ro­

ced u res w hich gave, th e b e s t r e s u l t s are d eser ib ed o :

P ot a ssiu m /hy d ro x id e ' c a t a l y s i s , : A <>2 go p o r t io n (0»075 •

m ole) ' Of p o ta ssiu m h yd rox id e p e l l e t s was f i n e l y ground in a. •

m ortar under 100 ml* o f dry b en z e n e .* The s lu r r y was r in s e d ■ .

in t o a 500 ml* f l a s k w ith 260 ml <, o f benzene * From t h i s ■ .

m ix tu re 100 m il o f benzene, was ^ and d isc a r d e d i n :

ord er t o remoye any w ater which,, may have b een p r e s e n t in . th e

p o ta ss iu m h y d ro x id e * To th e rem ain in g p o ta ss iu m h y d ro x id e -

benzene su sp e n s io n Was' added l O ^ g » . (:0<y05 m ole) o f b e n z ilg

a n d :th e ;,mixtpre was r e f lu x e d f o r 4 h o u rs0 A la r g e amount .

o f brow nish m a te r ia l p r e c ip i ta t e d .d u r in g t h i s tim e* The m ix­

tu r e was a llo w e d to c o o l and. 100: ml* o f d i s t i l l e d w ater was

added* The aqueous la y e r w a s: S ep a ra ted , and t h e benzene .

la y e r was wushed''W ith two / $ ..of w a ter 0 ■■■ The '.

aqueous la y e r s were Gomblned and a c i d i f i e d w ith 6 m l. o f

9M s u l f u r i c , a c id s The r e s u l t in g f lo c e u le n t w h ite p r e c i p i ­

t a t e was f i l t e r e d w ith s u c t io n and washed l i b e r a l l y w ith d i s ­

t i l l e d w a ters A fte r m ost o f th e w a ter had b e e n removed th e =

p rod u ct was d r ie d to c o n sta n t w e ig h t in an oven a t 100 t o

y i e l d - l i o l g r * (97^) ° f b e n z i l i c a c i d p m0p o l 5 0 Oo

Sodium- amide c a t a l y s i s * ' A 3 = 9 g* . ( 0*10 mole.) p o r t io n o f

sodium amide w as . added; d i r e c t ly to . a 500 ml * •three-neck f l a s k

c o n ta in in g 3(30 n il0:' o f dry benzene# The amide Has f lu s h e d

l ib e r a lly ^ w ith dry n itr o g e n du rin g th e a d d itio n # Im m ediate- >

• ly a fter w a r d '1 0 o 5 g# (0o05 m ole) o f b e n z i l was added# The' :

ap p aratu s was q u ic h ly ■ aasem bleds and th e mixtur^^e was r e f lu x -

.edj w ith s t i f f i n g , f o r th r ee . hqurSo A l a y e f o f 'b r o w n ish -r e d

m a te r ia l p r e c i p i t a t e d . d u rin g t h i s tim e# The m ixtu re, was;

, hydro l y zed ,; and th e prod u ct i s o l a t e d , and d r ie d as in . th e 'ret,.#,

ac t Ibh "with . po t as slu m : hyd n oxid e,# Y ie ld 7 o0 g# ( 61%) o f

b e n z i l i c acid ,- m.p«i 1480 , A' q u a l i t a t iv e t e s t , f o r n itr o g e n

. was n e g a tiv e # ' ' : ' ■ yy/" -v ' '' : rvy: ' _. ■ - ". V:

P re p a r a tio n o f sodium a n i l i d e o In a"500 ml# th r e e -n e c k " v

f l a s k f i t t e d w ith a r e f lu x c o n d e n ser , . H ershberg s t i r r e r , and .

'dropping; fu n n e l we,fe, p ia c e d 3:00 m l; e f 'dry 'b en zen e , 9#3 g#

(9*1 m l* , 0*1 mole.) -o f' a n i l in e j and 4*6 g* (0*2 m ole) o f

f r e s h l y cu t sodium* The m ix tu re was s t i r r e d and h e a te d to

th e - .r e f lu x tem p eratu re * At t h a t p o in t a s o lu t io n o f 11 * 3 g*

(10 *2 ml * @ 0*1. m ole ) o f c h lo f obenzene i n 50 ml * / o f dry b en ­

zene w a sa d d e d over a p e r io d o f 2 h o u r s* . The m ix tu re was r e -

f lu x e d an a d d it io n a l 4 hours a n d .th e n was a llo w ed to coo l*

I t w as ob served t h a t . abbut . o n e -h a lf■ o f th e sodium had n o t

r e a c t e d , ; so ..I t was. removed by . f i l t e r i n g th e su sp e n s io n

. th fo u g h .a sm all., q u a n tity o f g la s s w o o l, v h ic h was, p ofou s

’ enough t o . a llow - th e sodium a n i l ld e to run th ro u g h , b u t t o

, r e ta in ' t h e . unreacted . sodium*, /, 1 ' : x ; y ; - y :

. C a ta ly s is by so drum a i i i l i d e .: To th e su sp e n s io n o f sodium

a n i l id e was added j?o25 g« (Oo02:5 m ole) o f h e n z l lo The m ix­

tu r e w a s 's t ir r e d ' and h ea ted a t ..the r e f lu x tem p eratu re fo r 3

hotirSs th en a llo w ed to c o o l s l i g h t l y 6. The p rod u ct was i s o ­

l a t e d as i n th e p r e v io u s exp erim en ts $ to y i e l d 3 0 6 g r . ( 62.%)

o f b e n z i l l c aoido The crude p rod u ct was r e c r y s t a l 11zed

''from d i s t i l l e d w ater and m elted sh a r p ly a t 14.9°« , ; ' ■ : .

P r e p a r a tio n o f : sodium y -» m eth y la n ilid e . The b a se was p r e - .

pared from Ei-methyl a n i l in e ( f r e e o f a n i l in e and : -H, 35 - dime t h y l ~

a n l l in e ) in th e same manner i n w h ich sodium a n i l id e was ob­

t a in e d , .. The f o llo w in g , q u a n t i t ie s Were u sed : H -m e th y la n il in e s

lOo? -go. (1 0 09, mio 0 o 1 m o le ) | sodium , h , 2. 6 C (0®2: m ole) |

ch lorob en zen ev H o 3 go (10o2: m le, O el m o le ) | and a t o t a l o f

350, mlo o f b en z e n e « The tm rea cted sodium was removed by

f i l t e r i n g th e p u rp le s lu r r y th rou gh g la s s w o o l,

.C a ta ly s is : by sodium Ef-m ethylani 11 d e , D ecom p osition w ith .■: :

w a te r o To th e su sp e n s io n o f b a se was added 5®25 g« (0 ,0 2 5

m o le ) o f benzllLg and t h i s m ix tu re was s t i r r e d and r e f lu x e d •

f o r 3 h o u rs , Upon h y d r o ly s is and i s b l a t i o n o f th e p ro d u ct,

2 01|. go (42^). o f b e n z i l l c a c id was obtained^ The crude p rod­

u c t was r e c r y s t a l l i z e d from w ater and m elte d sh a r p ly a t . '

^ o 0 . v •. : : .

B i D ecom position - W ith ' dry HClo,' To th e su sp e n s io n o f b a se

: Was added: 5<jH5 g= ’ ( 0 ,025 .m ole) Of b e n z i l , ' and::t h i s m ixtu re ':

was s t i r r e d and r e f lu x e d f o r ,,3 h o u r s , The f 1 ask was a llo w ed ..

to e o o l and dry hydrogen c h lo r id e w a s. s lo w ly in tr d d u c ed in t o

th e f l a s k above th e su r fa c e o f th e l iq u id s w h ile th e m ix tu re

Was s t i r r e d v ig o r o u s ly d v e n ;a $>'b^ibd o f one h o u r , A fter ,

s ta n d in g fo r lb h ou rs th e iu ix tu re was f i l t e r e d . The f i l ­

t r a t e was c a r e f u l ly e x tr a c te d W ith th r e e 100 m l, p o r t io n s

o f a s a tu r a te d sodium carb on ate s o lu t io n . The carb on ate

e x tr a c t s were, com bined and washed w ith th r e e 50 ml:, p o r t io n s

o f e th e r s and th en a c i d i f i e d c a r e f u l ly w ith d i l u t e • s u lfu r ic

a c id . Upon i s o l a t i o n o f th e p rod u ct 0 ,6 g , .(10 ,5% ) o f b en -

& 111c • a c id Was o b ta in e d e The prodUct :was r e c r y s t a l i i 2ed . ,,

from d i s t i l l e d w ater and m elted sh a r p ly at l h 9° » '

P r e p a r a tio n o f sodium p h en o x ld e , . The .base was prep ared by .

th e d ir e c t r e a c t io n o f sodium and p h en o l i n b e n z e n e , . The

■ fo llow in g q u a n t i t i e s were used? -phenols 9 olt- gy ( 0 ,10 m o le ) ; ■

sodiums 2 ,3 g , ( 0 ,1 m q le); and. a t o t a l o f 350 m l, o f b en zen e .

A fte r s t i r r i n g a t th e r e f lu x tem p eratu re fo r 6 hou rs th e

u n r e a c te d sodium was removed by f i l t e r i n g th e su sp e n s io n

th r o u g h ; a c le a n w ire g a u ze , y . . ' y d - - , :

C a ta ly s is ' by sodium p h eh o x id e . To th e su sp e n s io n o f b ase

was added 5<> 25 g , (0,025 m ole) o f b e n z i l and th e m ixture

was s t i r r e d and r e f lu x e d fo r 3 h o u r ss th en , h y d ro ly z ed as

u s u a l , .Upon a c i d i f i c a t i o n w ith d i lu t e , s u l f u r ic a c id th e

s o lu t io n tu r n e d c lo u d y 5, bu t no f i l t e r a b l e p r e c i p i t a t e w as

o b ta in e d . I t .was con clu d ed th a t th e rearrangem ent had

tak en p la c e o n ly to an i n s i g n i f i c a n t e x t e n t .

ji mechanism has been po s t u la t e d f o r the: benz 111 o a c id - -

rearrangem ent w h ich se e k s t o b e t t e r e x p la in th e r o le o f th e

b a se in b r in g in g about th e r e a c tio n .' e s s e n t i a l f e a tu r e

o f th e fu n c t io n o f th e b ase i s th e fprm atiori o f : - an in t e r n a l

hydrogen bond betw een th e two ca rb o n y l•g ro u p s o f b e n z i l e

P r e lim in a r y wprfc i n d ic a t e s 3 a lth o u g h n o t c o n c lu s iv e ly , th a t

th e p o s t u la t e d m echanism i s c o r fe c t» .. t t

• One advantage o f th e proposed mechanism i s th a t i t p ro ­

v id e s an e x p la n a t io n o f th e o b s e r v a t io n s , t h a t h yd rox id e io n s

amide io n , -ammonias and to a c e r ta in - extent^ th e s o lv e n t w a i­

t e r a lo n e (8 ) 5, cau se th e rearran gem en t5 w h ile e th o x id e and

ph en oxid e io n s do n o t <, From t h i s m echahlsm I t can be p r e -

d ic te d th a t any s tr o n g b ase o f t h e type: uB-r-iH w i l l s u c c e s s -

f u l l y c a ta ly z e th e p r o d u ctio n o f b e n z i l i e a d d from b e n z il*

i f th e atom B i s su ch as to a l lo w 'th e hydrpgen. atom to e n te r

in t o hydrogen bond fo rm a tio n s I t i s a ls o p o s s ib le th a t a ;

b a se o f th e typ e iB-H-H,, such as sodium ! -d ip h e n y lh y d ra -

.zlde-j w i l l a ls o p a r t i c ip a t e i n ; th e b e n z i l i e a c id rea rra n g e ­

ment 3 and more r e a d i ly th an sod iu m ■a n i l i d e ? s in c e th e hydro­

gen bonded in te r m e d ia te would c o n ta in a f i v e - s i d e d r in g

r a th e r th an th e more s t r a in e d fo u r - s id e d hydrogen bonded

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