Abstract
Although meta-substituents on diphenyl ethers block attack at the para-position in the reaction with phosphorus trichloride and aluminium chloride, in some cases phosphorylation occurs in the even sterically more shielded ortho-position, leading to mixtures of isomeric phenoxaphosphinic acids. This effect and the obtained ratios of isomers can be explained by different substituent directive effects in a two step reaction mechanism.