Trifluoroperacetic acid is one of the strongest reagents used for Baeyer–Villiger oxidations, as a consequence of its high acidity relative to similar peracids and peroxides. This reaction converts ketones to either straight-chain esters or lactones, and is named for Adolf von Baeyer and Victor Villiger, who first reported it 1899. The reaction is believed to proceed via a Criegee intermediate and demonstrates good regioselectivity and chemoselectivity for the position of oxygen atom insertion, along with retention of stereochemistry at the adjacent position, as can be seen in the following example. The disodium phosphate () is added as a pH buffer to prevent the highly acidic trifluoroacetic acid byproduct from causing hydrolysis or transesterification of the ester product.