| Abstract
| - The gas-phase elimination kinetics of the title compounds have been examined over the temperature range of 310−369 °C and pressure range of 50−130 Torr. The reactions, in seasoned vessels, are homogeneous, unimolecular, and follow a first-order rate law. The products are methanol and the corresponding methyl ketene acetal. The rate coefficients are expressed by the Arrhenius equation: for trimethyl orthoacetate, log k1 (s−1) = [(13.58 ± 0.10) − (194.7 ± 1.2) (kJ mol−1)](2.303RT)−1r = 0.9998; and for trimethyl orthobutyrate, log k1(s−1) = [(13.97 ± 0.37) − (195.3 ± 1.6) (kJ mol−1)](2.303RT)−1r = 0.9997. These reactions are believed to proceed through a polar concerted four-membered cyclic transition state type of mechanism.
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