We prepared α-substituted carboxylic acids and ethyl esters and studied the effects of these compounds on the growth of lettuce seedlings. Compounds with shorter alkyl chains inhibited growth more than those with longer alkyl chains. α-Phenoxybutyric acid or its ethyl ester at 1 ppm caused as much inhibition as the corresponding unsubstituted acid and its ester at 1000 ppm. An electron-attracting Cl group introduced into the α-phenoxy group caused stronger inhibition than the electron-donating H or CH3 groups. α-Phenoxypropionic acid, α-(2, 4-dichlorophenoxy)-butyric acid, α-(2, 4-dichlorophenoxy) valeric acid, and their ethyl esters might be useful as herbicides and α-(2, 4-dimethylphenoxy) stearic acid and α-phenoxystearic acid might be useful as growth-promoting substances.
