Aldehyde---A2-Butenal

In this reaction which may apparently be brought about in one step, though aldol is undoubtedly an intermediate product even when it is 

Other reactions support this constitution for crotonic aldehyde. 

Geranial.—Corresponding to the higher ethene alcohol geraniol (p. 167) is the aldehyde derived from it and known as geranial. It has the constitution 

This compound and a related one known as citronellal belong with geraniol in the class of terpenes and will be considered in Part II. 

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