Chem 125 Lecture 24 10/28/05 Projected material 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 from the lecture.

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Trouble in Paradise C 7 H 5 O HC 7 H 5 O ClClH Cl +=+ C 7 H 5 O Cl + - H Cl + - The electronic character of radicals was troublesome for Coulombic dualism. ++ C 7 H 5 O H ? e.g. preparation of benzoyl chloride

1830s s Substitution or Type or Unitary Theory

Tuileries Bal costumé au Palais des Tuileries Musée d'Orsay ( Violently irritating fumes from wax candles spoil soirée at the Tuileries Palace (~1830) Dumas identifies the culprit as HCl from bleached wax.  organic compounds can "fix" chlorine!

How could wax "fix" chlorine? Cl **  C CH2H2 H2H2 + ** n + Addition of Cl 2 to an Alkene Cl C C H2H2 H2H2 C C H2H2 H2H2 (actually both steps at once)

How could wax "fix" chlorine? Substitution of Cl for H H CH 3 Cl weak bond (58 kcal/mole) SOMO H Cl CH 3 Cl CH 3 Cl Cl single-electrons single-barbed arrows  "free-radical chain" Cl C CH2H2 H2H2 + Addition of Cl 2 to an Alkene Cl C C H2H2 H2H2 C C H2H2 H2H2

C 2 H 3 O OHC 2 H 2 ClO OH Photochlorination of acetic acid transmuted the acetyl "element". ClH Cl +=+ C 2 H 3 O OHC 2 H 2 ClO OH More Trouble for Radicals - Dumas (1839) Hydrogen may be substituted by an equivalent amount of halogen, oxygen, etc. Similar Acids! C 2 HCl 2 O OH C 2 Cl 3 O OH without changing molecular type.

Four Types Recognized by 1853 H H H Cl H H O H H NH C2H5C2H5 H O C2H5C2H5 H NH K C2H5C2H5 C2H5C2H5 C2H5C2H5 I + = C2H5C2H5 C2H5C2H5 O + KI Williamson Ether Synthesis (1850)

Butyl_Bromide Two-Word Relic of Radical Dualism Bromobutane One-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…”

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 + C 4 H 6 O 3 ] [Cl 2 Cl 2 + Cl 8 Cl 6 Cl 6 ] [MnCl 2 + C 4 Cl 6 O 3 ] [Cl 2 Cl 2 + C 4 Cl 6 O 3 ][MnO + C 4 Cl 6 O 3 ]

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. Ch. 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 ) CH 3 CO 2 HCH 3 CO 2 H + + but molecular weight would show he had its dimer H 3 C-CH 3 (Cannizzaro, 1860)

Ironically the key reactions of both radical and type theories did involve free radicals (SOMOs)

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Kirkintolloch (near Glasgow)

Archibald Scott Couper ( ) Dilettante Edinburgh/Berlin Classics, Metaphysics Logic, Moral Philosophy, Concerts 1855 Chemist Berlin 1856 Chemist Paris (Wurtz) - Salicylic Acid Fired Mental Invalid 1858

Theory and Types

p on the French Type Theory Should the principle which is therein adopted be applied to the common events of life, it will be found that it is simply absurd. Suppose that some one were to systematize the formation of letters into words that formed the contents of a book.

p on the French Type Theory Were he to begin by saying that he had discovered a certain word which would serve as a type, and from which by substitution and double decomposition all the others are to be derived, - that he by this means not only could form new words, but new books, and books almost an infinitum, - he would state certainly an empirical truth.

p on the French Type Theory At the same time, however, his method would, judged by the light of common sense, be an absurdity. But a principle which common sense brands with absurdity, is philosophically false and a scientific blunder.

p on the German Radical Theory I can only remark that it is not merely an unprofitable figure of language, but is injurious to science, inasmuch as it tends to arrest scientific inquiry by adopting the notion that these quasi elements contain some unknown and ultimate power which it is impossible to explain.

p on the German Radical Theory It stifles inquiry at the very point where an explanation is demanded, by putting the seal of elements, of ultimate powers, on bodies which are known to be anything but this. but imprudent and undiplomatic, especially from a newcomer. Absolutely true

Science demands the strict adherence to a principle in direct contradiction to this view. That first principle, without which research cannot advance a step, dare not be ignored; namely, that a whole is simply a derivative of its parts. p Look to the Elements [?]

End of Lecture 24