Kinetics of the Unimolecular Elimination of Chlorobutanones in the Gas Phase

Article abstract of DOI:10.1021/j150626a037

The gas-phase unimolecular elimination of 3-chloro-3-methyl-2-butanone has been investigated, in a static system and seasoned vessel, over the temperature range of 340-395 deg C and the pressure range of 60-190 torr.The reaction is homogeneous and unimolecular, follows a first-order rate law, and is invariable in the presence of cyclohexane, a radical-chain inhibitor.The products are isopropenyl methyl ketone and hydrogen chloride.The rate coefficients are given by the Arrhenius equation log k₁ (s^-1) = (12.56+/-0.31)-(190.8+/-3.7) kJ mol^-1 (2.303RT)^-1.When primary, secondary, and tertiary chlorobutanones are compared the presence of acetyl at the C_β-Cl bond causes a significant rate enhancement due to the -M effect.However, if this substituent is at the C_α-Cl bond , deactivation in rate of elimination of these compounds is observed.The present work could well provide a general view on the effect of the acetyl substituent at the C_α-Cl and C_β-Cl bonds in the molecular elimination of haloketones in the gas phase.