Chem 125 Lecture 2210/27/08
This material is for the exclusive use of Chem 125 students at Yale and
may not be copied or distributed further.
It is not readily understood without reference to notes or the wiki from the lecture.
1832
Radical Theory
Oil of Bitter
Almonds
Toward Structure With Analysis?
Oil ofBitter
Almonds
C7H6O2O2
C7H5OClCl2
Liebig & Wöhler (1832)
C7H6O
C7H5OBr
Br2
C7H5OIKI
C7H7ONNH3
C14H10O2S
PbS
So?Persistence of C7H5O Benzoyl Radical
Bz • H
Bz • OH
Bz • Cl
Bz • Br
Bz • I
Bz • NH2
Bz2 • S
Organic Dualism
A radical can be the “base” of more than just an acid!
During the 1830s compound radicals were discovered
everywhere:Liebig: Acetyl
Bunsen: Cacodyl (Me2As •)
Piria: Salicyl
Dumas: Methyl Cetyl Cinnamyl Ethylene
Ethyl (Berzelius)
e.g. Ethyl Chloride
-yl from (wood , matter)
ether from (to shine) 1700s
hence eth yl (Liebig, 1834)
Dualistic Radical Theory Survives
Two Words (+ and -)in our Nomenclature
sky
colorless liquid
meth- from (wine, spirit)
-yl from (wood, matter)
-ene Greek Feminine
Patronymic"daughter of"
from
(1840) CH3 methyl from methylene
"Daughter of wood spirits"
hence meth yl ene (Dumas, 1835)
CH3OH = CH2 + H2O
(1852) ethylene C2H4
: ethyl :: methylene : methyl: C2H5 :: CH2 : CH3
C3 C4
C3H7 PropylC3H6 Prop(yl)ene
C4H9 ButylC4H8 But(yl)ene
From C3 Propionic Acid (1847)
(protos first) (pion fat)Derivatives of acids with >C2 were like fats,
unlike C1 (formic) and C2 (acetic)
From C4 Butyric Acid (1826)
Lat. butyrum (butter)from rancid butter
Jean-Baptiste
André Dumas
(7/14/1800-1884)Post-Napoleonic
Guardian ofFrench Chemistry
Persistent Opponentof Liebig and
Berzelius
Chaired Professor:Sorbonne 1841-
École Polytechnique 1835-École de Médicine 1839-
http
://c
lend
enin
g.ku
mc.
edu
Note on the Present State of Organic Chemistry by MM. Dumas and Liebig (1837)
Sixty years have hardly passed since the ever memorable time when this same assembly heard the first discussions of the fertile chemical doctrine which we owe to the genius of Lavoisier. This short span of time has sufficed to examine fully the most delicate questions of inorganic chemistry, and anyone can easily convince himself that this branch of our knowledge possesses almost everything that it can with the methods of observation available.
…there barely remain a few cracks here and there to fill in.
MYOPIA!
(cf. Lavoisier, “in our own time”)
In a word, how with the help of the laws of inorganic chemistry can one explain and classify such varied sub-stances as one obtains from organic bodies, and which nearly always are formed only of carbon, hydrogen, and oxygen, to which elements nitrogen is sometimes joined?
This was the great and beautiful question of natural philosophy,
prin
tart
ist
Note on the Present State of Organic Chemistry by MM. Dumas and Liebig (1837)
Note on the Present State of Organic Chemistry by MM. Dumas and Liebig (1837)
a question well designed to excite the highest degree of competition among chemists; for once resolved the most beautiful triumphs were promised to science. The mysteries of plants, the mysteries of animal life would be unveiled before our eyes; we would seize the key to all the changes of matter, so sudden, so swift, so singular, that occur in animals and plants; more importantly we would find the means of duplicating them in our laboratories.
Note on the Present State of Organic Chemistry by MM. Dumas and Liebig (1837)
Well, we are not afraid to say it, and it is not an asser-tion which we make lightly: this great and beautiful ques-tion is today answered; it only remains to follow through on all the consequences which its solution entails... In fact to produce with three or four elements such varied combinations, more varied perhaps than those which make up the whole inorganic kingdom, nature has chosen a path as simple as it was unexpected; for with elements she has made compounds which behave in all their properties like elements themselves. And this, we are convinced, is the entire secret of organic chemistry.
Note on the Present State of Organic Chemistry by MM. Dumas and Liebig (1837)
Thus organic chemistry possesses its own elements, which sometimes play the role of chlorine or oxygen in inorganic chemistry and sometimes, on the contrary, play the role of metals. Cyanogen, amide, benzoyl, the radicals of ammonia, of aliphatics, of alcohol, and analogous substances, these are the true elements with which organic chemistry operates…
To discover these radicals, to study them, to characterize them, this has been our daily study for ten years.
+
Note on the Present State of Organic Chemistry by MM. Dumas and Liebig (1837)
Sometimes, none the less, our opinions have appeared to differ, and then, with each of us drawn on by the heat of our battle with nature, there arose between usdiscussions whose liveliness we both regret.
Actually when we were able to discuss questions which separated us in several friendly meetings, we soon realized that we were in agreement on the principles...
We then understood that united we could undertake a task before which either of us in isolation would have recoiled…
We will analyze every organic substance…to establish reliably what sort of radical it refers to…
Note on the Present State of Organic Chemistry by MM. Dumas and Liebig (1837)
Each of us has, in fact, opened his laboratory to all young men who were motivated by true love of science; they have seen all, understood all. We have worked under their eyes, and have had them work under ours, in such a way that we are surrounded by young rivals, who are the hope of science, and whose work will be added to ours
and mingle with ours, for it will have been conceived in the same spirit and carried out by the same methods…This is not an effort conceived for personal gain or in the interest of narrow vanity. No, and in a collaboration which is perhaps unheard of in the history of science, this is an undertaking in which we hope to interest every chemist in Europe. (unimaginative megalomania)
Trouble in Paradise
C7H5O • H C7H5O • ClCl H • Cl+ = +C7H5O • Cl+ -
H • Cl+ -
The electronic character of radicals wastroublesome for Coulombic dualism.
++C7H5O • H
?
e.g. preparation of benzoyl chloride
1840s - 1850s
Substitutionor Type or Unitary
Theory
Tuileries
Bal costumé au Palais des Tuileries. 1867
organic compounds can
"fix" chlorine gas!
Violently irritating fumes from wax
candles spoil soiréeat the Tuileries Palace (~1830)
Dumas identifies the culprit as HCl from wax that had
been bleached by Cl2.
Mus
ée d
'Ors
ay (
ww
w.h
isto
ire-
imag
e.or
g)
cough!choke!
Two ways wax could "fix" chlorine:
Cl Cl*
C
CH2
H2
+*+
Addition of Cl2 to an Alkene (HOMO/LUMO)
ClC
CCl
H2
H2
C
C
H2
H2Cl
Cl
(actually both steps at once)
Cln
••
••
••
HOMOLUMO LUMOHOMO
HOMO / LUMO
“olefiant gas” “oil of Dutch chemists” (1795)
Free-Radical Substitution of Cl for H (SOMO)• •
Two ways wax could "fix" chlorine:
H CH3Cl Clweak bond
(58 kcal/mole)
••
SOMO
H Cl
•
CH3 Cl Cl
CH3Cl
•
Cl
single-electrons
single-barbedarrows
"free-radical chain"
Cl ClC
CH2
H2
+
Addition of Cl2 to an Alkene (HOMO/LUMO)
ClC
CCl
H2
H2
C
C
H2
H2Cl
Cl
No high HOMO!“make-as-you-break”
“make-as-you-break”
Still hard to break!
Use light to promote an electron to *Cl-Cl
lots of product from one initial photolysis
1830s - 1850s
“Substitution”or “Type”
or “Unitary”Theory
C2H3O • OH C2H2ClO • OH
Photochlorination of acetic acidtransmuted the acetyl "element".
Cl H • Cl+ = +C2H3O • OH C2H2ClO • OH
More Trouble for Radicals - Dumas (1839)
Hydrogen may be substituted by anequivalent amount of halogen, oxygen, etc.
Similar Acids! C2HCl2O • OH
C2Cl3O • OH
without changing molecular type.
Four Types Recognized by 1853
H
H
H
Cl
H
HO
H
HN H
C2H5
HO
C2H5
HN H
KC2H5
C2H5
C2H5
I+ =
C2H5
C2H5
O + KI
Williamson Ether Synthesis (1850)
Butyl_BromideTwo-Word Relic
of Radical Dualism
BromobutaneOne-Word Relic
of "Unitary" Theory
Unitary (not Dualistic) Theory [Molecules are like] planetary systems held together by a force resembling gravitation, but acting in accord with much more complicated laws. Dumas (1840)
Formulae…may be used as an actual image of what we rationally suppose to be the arrangement of constituent atoms in a compound, as a orrery is an image of what we conclude to be the arrangement of our planetary system. A. W. Williamson (age 27, 1851)
A Philosopher lecturing on the Orrery Joseph Wright of Derby (1766)
A neutral anhydrous tartrate loses an atom of water at +190°; it has ceased to be a tartrate and has become another salt
Berzelius (1838)
“By reacting chlorine with ordinary ether [Dumas] pro-duced a very interesting compound which he reckoned, according to the theory of substitutions, to be an ether in which 4 atoms of chlorine replace 4 atoms of hydrogen. An element as eminently electronegative as chlorine would never be able to enter into an organic radical : this idea is contrary to the first principles of chemistry…”
first use of “R” to denote a generalized radical
“Liebig’s Annalen”
I am a far cry from sharing the ideas that M. Dumas
has linked to the so-called laws of
the substitution theory.
1840
On the Reaction of Chlorine with the Chlorides of Ethanol
and Methanol and Several Points of the Ether Theory.
On the Substitution Lawof M. Dumas.
Remarks on the Previous Paper
Can one substitute the elements that play their role in any
simple or compound substance equivalent for equivalent ?
On the Law of Substitutions andthe Theory of Types.
Justus Liebig
*) Letter to J.L.
On the Law of Substitutions andthe Theory of Types.*
YES!
On the Substitution Law and the Theory of Types
(letter to Justus Liebig) Paris, 1 March 1840
Monsieur! I am eager to communicate to you one of the most striking facts of organic chemistry. I have confirmed the substitution theory in an extremely remarkable and completely unexpected manner. Only now can one appreciate the great value of this theory and foresee the immense discoveries that it promises to reveal.
manganese acetate [MnO + C4H6O3]
[Cl2Cl2 + Cl8Cl6Cl6]
[MnCl2 + C4Cl6O3]
[Cl2Cl2 + C4Cl6O3]
[MnO + C4Cl6O3]
On the Substitution Law and the Theory of Types
(letter to Justus Liebig)
For all I know, in the decolorizing action of chlorine, hydrogen is replaced by chlorine, and the cloth, which is now being bleached in England, preserves its type accor-ding to the substitution laws.* I believe, however, that atom-for-atom substitution of carbon by chlorine is my own discovery. I hope you will take note of this in your journal and be assured of my sincerest regards, etc.
S. C. H. Windler
* I have just learned that there is already in the London shops a cloth of chlorine thread, which is very much sought after and preferred above all others for night caps, underwear, etc.
*
In 1849 Kolbe Prepared Free Methyl Radical
(electrolysis)
CH3 • CO2H CH3 CO2 H+ +
but molecular weight would showhe had its dimer H3C-CH3
(Cannizzaro, 1860)
CO
HC
O
OH
O2
CO
OHC
O
OH
Cl2H3C CH2Cl
CO
OCH3
-e-
H3C CH3-CH3•
Ironically the key reactions of both radical and type theories did involve free radicals
(SOMO not HOMO/LUMO)
CO
•
CO
OHH2C
•
End of Lecture 22Oct. 27, 2008