A kinetic investigation of the hydroxide-catalysed detritiation of various [16-3H]-15,16-dihydrocyclopenta[a]phenanthren-17-ones and related compounds

Abstract

The hydroxide-catalysed detritiation rate constants from the C-16 position of a series of substituted [16-³H]-15,16-dihydrocyclopenta[a]phenanthren-17-ones have been measured in a 90 : 10 (v/v) water-dioxane mixture at 25 °C. The results show that methyl group substitution brings with it, in addition to the customary deactivating effect, a marked acceleration in rate, which probably has its origin in steric strain considerations. Similar studies involving the analogous position in a number of related ketones (benz[e]indanone, indanone, and cyclopentanone) show that the rates are not simply a function of the number of additional benzene rings but depend on their position relative to the cyclopentanone system.