132 POPULAR SCIENCE MONTHLY 



had a head near the oscillation frequency 3,700. As the molecule is 

 lighter than that of ethyl aceto-acetate, we should, from previous ob- 

 servations, expect the band to be shifted farther from the red; the 

 opposite, however, is true and the only explanation that seems possible 

 is that the band is the result of a new kind of vibratory motion arising 

 between two carbonyl groups when in close proximity to each other. 

 In order to substantiate these conclusions other derivatives containing 

 two carbonyl groups were studied. But as the carbonyl group in 

 carboxyl has not all the characteristics of a true carbonyl group, atten- 

 tion was turned to the compound diacetyl, CH 3 — CO — CO — CH 3 . 

 Here the absorption band occurs at the oscillation frequency 2,400 

 (wave-length 4,170 A.U.), which is in the visible blue region of the 

 spectrum, and hence this absorption of colored rays must result in the 

 compound itself taking on the complementary color — that of yellow. 

 In the same way it can be shown that glyoxal, OHC — CHO, gives an 

 absorption band in the visible blue region, and consequently its dis- 

 tinct yellow color may be explained. Oxalic acid, HOOC'COOH, 

 however, with a hydroxyl group next to each carbonyl group and there- 

 fore analogous to pyruvic ester, gives no band in the visible spectrum, 

 and is, therefore, colorless. 



Upon the theory that a change in linking produces the absorption 

 bands, the only possible explanation would be indicated as follows : 



CH 3 — O— C— CH S CH 3 — G=C— CH 3 



U * u 



The make-and-break contact between the oxygen atoms would give 

 marked activity to these atoms. Such a process other than tautomer- 

 ism, where a wandering of a labile atom is suggested, has been named 

 by Stewart and Baly 3 " isorropesis " (equipose), and differs from the 

 former in that the head of its absorption band lies much nearer the red 

 end of the spectrum or almost in the visible violet region. With the 

 diketone known as benzil, C 6 H 5 — CO — CO — C 6 H 5 , an absorption 

 band with head at the oscillation frequency 3,900 was noticed in solu- 

 tions of small concentrations. This would seem to indicate the 

 presence of a certain amount of oscillation due to the benzol nucleus. 

 The residual affinities of the two carbonyl groups are undoubtedly fixed, 

 to some extent, by the free affinities of the benzol molecule, but even 

 so there may be present a small amount of isorropesis between the two 

 carbonyl groups. That such is really the case is demonstrated in solu- 

 tions of greater concentration by the presence of a very shallow absorp- 

 tion band with head at the oscillation frequency 2,650. Its shallow- 

 ness, however, argues for only a slight isorropesis; indeed the color of 

 benzil, which is but faintly yellow, may be made to disappear entirely 



* Chem. Soc. Trans., 89, 498, 1906. 



