Gas-Phase Pyrolysis Kinetics of 2-Substituted-2-Propyl Acetates. Effect of Substituents on the α-Carbon of Tertiary Acetates

Article abstract of DOI:10.1021/j100438a003

Three 2-substituted-2-propyl acetates undergo a homogeneous, first-order, unimolecular elimination in the gas phase at temperatures from 230 to 340 deg C and pressures from 56 to 210 mmHg.The rate constants are expressible by the Arrhenius equation: for 2,3,3-trimethyl-2-butyl acetate, log k (s^-1) = (14.40 +/- 0.49) - (171.5 +/- 4.6) kJ mol^-1 (2.303RT)^-1; for α-acetoxyisobutyronitrile, log k (s^-1) = (14.45 +/- 0.82) - (198.7 +/- 8.8) kJ mol^-1 (2.303RT)^-1; for methyl α-acetoxyisobutyrate, log k (s^-1) = (12.53 +/- 0.32) - (176.1 +/- 3.6) kJ mol^-1 (2.303RT)^-1.The Taft correlation for the pyrolyses of tertiary esters with substituents on the α-carbon is projected and discussed.Many of these substituents enhance the elimination by steric accelaration.