102096-25-3Relevant articles and documents
Kinetics and Mechanism of the Lewis Acid-catalyzed Addition of Alcohols to Ketenes in Diethyl Ether Solution
Poon, Nai L.,Satchell, Derek P. N.
, p. 1551 - 1554 (2007/10/02)
A kinetic study is reported of the addition of alcohols to dimethyl- and diphenyl-ketene in diethyl ether solution at 25 deg in the presence of HgCl2, ZnCl2, SbCl3, and Bun2SnCl2.Except for HgCl2, which forms insoluble complexes with the reactants, the metal halides catalyse the addition to dimethylketene.The catalysed addition involves the reaction of metal halide-alcohol adducts with the ketene.In general, the stronger the adduct as a Broensted acid, The faster is the addition of the alcohol to the ketene, although C-O, as well as C-H, bond formation is propably significant kinetically.A cyclic transition state is suggested.For diphenylketene, strongly acidic adducts transfer alcohol to the ketene so slowly that inhibition of alcoholysis is observed.Inhibition arises because the spontaneous alcoholysis is reduced as free alcohol is removed as unreactive adduct.However, weak-metal halide acids probably lead to catalysis.It is concluded (a) that the different behaviour of the two ketenes in these reactions is in keeping with their behaviour observed when they react with carboxylic acids in ether, and (b) that metal halide-catalysed alcoholysis of ketenes is generally similar to that observed with aryl isocyanates, except that tin-based catalysts are relatively more effective with isocyanates.
