Raman Spectra of Hydrocarbons IV. 2,5-Dimethyl-1,5-Hexadiene and 2,5-Dimethyl-2,4-Hexadiene

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Abstract
Raman frequencies, relative intensities, and depolarization factors are given for (A) 2,5-dimethyl-1,5-hexadiene and (B) 2,5-dimethyl-2,4-hexadiene. The relative intensities and depolarization factors were obtained with the aid of a Gaertner microdensitometer. The two molecules are isomers, each containing eight carbon and fourteen hydrogen atoms. (A) contains two XYC=CH2 groups and (B) contains two XXC=CHZ groups. In (B) the double bonds are conjugated, in (A) unconjugated. The results for the five olefinic frequencies are compared with data previously obtained for nine other olefins. The data for the olefinic lines of (A) are 1297(50), 1414(430)0.74, 1651(1000)0.21, 2977(580)0.28, and 3074(220)0.78, values which are in good agreement with those obtained previously for olefins containing an XYC=CH2 group. For (B) the olefinic frequencies are 1227(75)0.46, 1663(1000)0.18, 3012(vw), and 3040(vw) (vw = very weak). The conjugation thus resulted in a lowering of these frequencies of 19, 19, 0, and 10 cm−1, respectively, from the values of the corresponding frequencies of the XYC=CHZ group in dipentene.

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