Methyl substituted ethylenes spectrum

In all cases, the quantum yield of the molecular elimination of either methane or hydrogen is considered to be smaller than O.OS. Thus, the main primary processes involve either the a(C-C) or the P(C-H) bond ruptures. This observation differs from that made for ethylene, where at least 40% of the fragmentation involves the molecular elimination of hydrogen. May this behavior be linked to the differences observed in the absorption spectra At least, it may be said that well-defined absorption bands, one of which is probably Rydberg in nature, are observed in the ethylene spectrum. Conversely, the spectra of methyl substituted ethylenes are rather unstructured (1). The UV absorption spectrum of 1-butene is shown in Figure 4. We shall come back lat to diis point. 

The double bond, C=C —The double bond in ethylene and in substitution products of ethylene gives a Raman spectrum in the region 1,600 to 1,680 cm i. In ethylene the value is 1,620 cm, and on the introduction of methyl groups into the molecule the frequency increases, as shown in Table XLIV. In the di-substituted compounds the values for the cis and trans forms are different from each other and different from that in which both methyl groups are attached to the same carbon atom. This distinction may be used as a method of distinguishing between isomers. 

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