Nucleophilic displacements in substituted pyridine N-oxides. Part III. The light-catalysed reaction between 4-nitropyridine 1-oxide and piperidine in ethanol

Abstract

In the absence of light the reaction between 4-nitropyridine 1-oxide and piperidine in ethanol obeys strict second-order kinetics (k2= 6·23 × 10–6 l. mole–1 sec.–1 at 30°). Exposure to ultraviolet light (λ= 334 mµ) accelerates the reaction.Quantum yields varied from 0·2 to 0·5, and depended on piperidine concentration in accord with a ratedetermining displacement of the nitro-group by piperidine from an excited N-oxide species formed reversibly from the ground state.