Steric environments of radicals produced by addition of tert‐butoxyl radicals to dialkyl maleates as studied by spin trapping with 2,4,6‐tri‐tert‐butyl‐1‐nitrosobenzene

Abstract

Radicals produced by the addition of tert-butoxyl radicals to maleic esters were spin-trapped with 2,4,6-tri-tert-butyl-1-nitrosobenzene (BNB). Although this does not yield polymers, the radicals resulting from the former addition were further added to maleate thus extending the chain length to a limited extent prior to the reaction with BNB. Increasing the bulkiness of the ester alkyl group and the chain length brought about considerable steric hindrance against the reaction with BNB as evidenced by an increase in the amount of N-(alkoxy)phenylaminyl radicals in the spin adduct. The steric effect was found to arise already at the stage of short chain lengths (trimers): The radical consisting of two maleate units and bearing a tert-butoxy end group seems to be less hindered than the longer homologues.