The substituent effect in the fragmentation of phenylcyclohexanols

All the main fragmentation pathways undergone by trans-4- and trans-2-p-substituted phenylcyclohexanols have been studied, and the ionic abundances have been correlated with the σ constants. This analysis shows that electron withdrawing substituents, increasing the fraction of molecular ions having sufficient energy to decompose, favour all fragmentations. However, along with this ‘non-specific’ substituent effect, there is a ‘specific’ effect, in the opposite sense, increasing the formation of the [M—59]⁺ and [M—85]⁺ ions with increasing electron releasing power of the substituents. The loss of water, although it is almost exclusively a 1,4 elimination in the case of trans phenyl cyclohexanols, is not specifically influenced by the substituents.