o-nitrobenzyl photochemistry: Solution vs solid state behavior.

The efficiency of various 2-nitrobenzyl groups in the photogeneration of carboxylic acids from nitrobenzyl esters has been determined, and the solution vs. solid polymer matrix photochemistry is compared. Generally, the quantum yield for photoreaction is lower in the solid state, probably due to decreased conformational mobility. The substitution that affords the largest increase in quantum yield (phi) is at the alpha-carbon atom. The value of phi for alpha-methyl-2-nitrobenzyl trimethylacetate in solution is 0.65 vs 0.13 for the parent 2-nitrobenzyl ester.