Organotin(IV) compounds as intramolecular transesterification catalysts inthermal depolymerization of poly(L-lactic acid) oligomer to form LL-lactide

Mono-, di-, and tetraalkyl tin(IV) compounds were evaluated for the intramo lecular transesterification reaction of the thermal depolymerization of pol y(L-lactic acid) oligomer forming lactide by gas chromatography using a bet a-cyclodextrin stationary phase capillary column. The most active catalyst was found to be monobutyltin trichloride (BuSnCl3) (8), which contains tin- halogen bonds, and the least effective was the coordinatively saturated mon oorganotin derivative, monobutyltin tris(2-ethylhexanoate) (7). Cordination of the carbonyl group in the oligomer to the tin catalysts is an important factor influencing its activity.