Propene condensed structure

The question of the fate of the "Strecker" aldehydes requires an answer. By converting the amino acid phenylalanine to yield aroma compounds, phenyl acetaldehyde is liberated. Because of its phenyl ring it is a good detector compound. We were able to establish some of its reaction products. For example, we have identified, among others, phenylethylpyrazine, phenylfuran, phenylethylpyrrole and phenylpyri-dine. We assume that aldol condensations are responsible for the formation of these compounds. Figure 5 illustrates our assumption.We have identified several compounds the structures of which make probable an aldol condensation (3-(2 -furyl)-2-phenyl-2-propenal, phenyl hydroxyketones) likely. This assumption is supported by the identification of pyrazines with up to 5 carbon atom side chains in other experiments. 

In a series of papers Gross et provide experimental evidence that ionization of cyclopropane in the gas phase results in the formation of a trimethylene cation radical (2) isomerization of cold 2 to ionized propene (3) can be ruled out. The authors, moreover, stress that the structural changes of ionized cyclopropane in both the gas phase and in condensed phase are entirely analogous. 

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