Electron spin resonance and CNDO/2 study of the radicals produced during fast electron irradiation of substances containing nitrogen. Part 3.—Piperidine

Abstract

The fast-electron irradiation of piperidine in a matrix of adamantane, thiourea or molecular sieve results in the formation of only one identifiable radical species, piperidin-2-yl. The most stable conformer of this radical is the boat form but, except at low temperatures, it undergoes rapid inversion which exchanges the axial and equatorial hydrogens of the methylene groups adjacent to the N atom and the radical C atom. The inversion gives rise to a distinct alternating line width effect for each methylene group, from which activation energies of 35.5 ± 5 kJ mol^–1 and 22 ± 5 kJ mol^–1 can be derived for the processes.

CNDO/2 calculations predict hyperfine splittings for the boat form in very good agreement with those observed.