Photochemical substitution of ring hydrogen of pyridinecarboxylic esters by alkyl groups derived from solvent alcohols occurs in several paths: 1) alkylation initiated by the excited carbonyl moiety of the ester group and 2) alkylation initiated by the excitation of the π- electonic system of the pyridine ring. In the photoreaction of methyl 3-pyridinecarboxylate in acidic methanol, three types of excited state (two triplet states for alkylation and a singlet ...
