Acrolem n-Methylacroleit: 5Iesityl oxidt Phorone ~rotylidcr~eacrtori~
CH.=CHCHC, CH;z=CH(CHy)CHO 'CHj)?C=CHCOCH (CHIIJC -CHCOCH=X(CH j I CH CH - C H C H CFTCOCH H C
c
H (
,~-IonoliL
I'TI i CH
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HCOC"
.In exaniiiiatioii oi Figs. 5 aiid (ishows that the absorption spectra of these substarices are iiot much like those of oxidized linoleic acid. Special attention should be called to phorone and crotyildeneacetone. 'The former has the structure postulated by ScheiberYfor ail oxidation product of linoleic acid. Only iii alkaline solution does oxidized linoleic acid exhibit broad bands at 2700 and 3700 A. much like those of phorone but of different relative intensity. The bands of phorone and crotylideneacetorie are so iiitense that a fraction of one per ceiit. could account for all of the absorption a t 2700 A. shown by the most highly oxidized linoleic acid used in this study.
[CONTRIBUTIOX FROM
Summary 'The absorption spectra of ethyl liiiolatc, highly purified linoleic acid, and 10,12-liiioleic x i t i were studied before and after oxidation in iieutral :iiid alkaline alcoholic solutions. 2 . .lutoxidatioii of each of these compounds is >tccotiipaitied by an increase i i i the absorptioii at 27.50 A. which is not directly related t n peroxide vnluc. 3. ( kitlatioil of conjugated 1i;ioleic acid greatly reduces thc absorption at 2300 A . 4. Cool alkali has no effect upoil the absorption of the conjugated or unconjugated fresh fatty acids but produces market1 ch:mges in the oxidized products. .-I. ;ibsorption spectra of acrolein, a-methyl acroleiii, mesityl oxide, phorone, crotylideneacetone, and (3-ionone in alcohol and alkali 'are shown as examples of unsaturated conjugated carbonyl compounds. (j. The autoxidation products of linoleic acid are spectroscopically unlike those of oleic acid. I.
~ ~ I S Y E A P I : I I . I1-1, S
THE' D I V I S I O N OF PIIYSIOLOGICAL
CHEMISTRY,
bhSX.
RECEIVEDMARCH 1-1, 194-5
c % I V E R S I T Y OF MINNI.:SOTA]
Spectrophotometric Studies of the Oxidation of Fats. 111. Ultraviolet Absorption Spectra of Oxidized Octadecatrienoic Acids BY RALPHT. HOLXAN,' WALTER0. LUNDRERG~ AND GEORGE 0 . BURR
In previous investigations3s4 the changes of ultraviolet absorption spectra were followed during the courses of oxidation of fatty acids containing one or two double bonds. The present report presents the changes in spectrum induced by the oxidation of the fatty acids containing three double bonds, isolated or conjugated. Experimental The ultraviolet absorption spectra were determined using the Beckman quartz spertrophotometer. 98'; ethyl alcohol distilled over potassium hydroxide was used as solvent. After the spectra in alcoholic solutions w e n determined, 5.0 cc. of the alcoholic solutions were diluted hydroside, aiid the with 5.0 cc. of ZOi,;, aqueous potassiu~r~ spectra in alkali determined inmediately. Linolenic acid and ethyl linolenatc wcrc exposed to air in ail oven at G3", the temperature used iri an oven A h bility test! A second samplc of litiolenic acid which h a d (1) This paper is taken in part from a thesis presented by Ralph 'T. Holman to the Graduate Faculty oi t h e University oi Minnesota in partial fulfillment of the requiremeuts for t h e Ph.1). degree. June. 1944. The work was aided by grants from thewormel Research Foundation, t h e National Live Stock and Meat Board, aud t h e S a tional Dairy Council. (2) Present address: Hormel Institute, Austin, Minnesota. (3) R. T. Holman, W. 0. Lundberg, W. M ,1,auer a n d G . 0.Burr, TriIs J O U R N A L , 67, 1285 ( 1 9 4 5 ) . (4) R. T. Holman, W'. 0 1,undt)erX nnri C: 0. Hurr, %bid . 67, 13% Il045) $ 5 ) IV. 0. L u n d b r r g , I i ( 1 l l a i ~ ~ , r . ~ i
