trans-2-Benzal-6-methylcyclohexanone (III) and trans-2-benzal-5-methylcyclopentanone (VII) isomerize in the presence of acid to the endocyclic unsaturated isomers 2-benzyl-6- methyl-2-cyclohexenone (II) and 2-benzyl-5-methyl-2-cyclopentenone (VI) respectively. Structure proof and chemical conversions of II are described. Isomerization of III to its cis isomer IV was accomplished by light irradiation. It is shown how to distinguish by means of ...
