Experimentally determined barriers to O-acyl group topomerization in mixed anhydrides composed of β-disubstituted carboxylic acids and cyclic thiohydroxamic acid N-hydroxy-4- methylthiazole-2 (3H)-thione were located in the range of ΔG‡ 320= 68±8kJmol− 1 (DNMR). According to modeling studies, the underlying exchange process is proposed to occur via rotation about the N, O bond for torsional movement of the O-acyl group past the ...