Carboxylation of Toluene by CO2 Generating p-Toluic Acid: A Kinetic Look

A kinetic study involving stoichiometry, order of reaction, rate constants (k), and rate laws has been performed on carboxylation of toluene by CO, generating p-toluic acid by two routes: (a) Friedel-Crafts reaction, C6H5-CH3 + CO2 + Al2Cl6 -> CH3-C6H4-COOAl2Cl5 + HCl and (b) Friedel-Crafts reaction with incubation method involving two steps, CO2 + Al2Cl6 -> CO2:Al2Cl6 and CO2:Al2Cl6 + C6H5-CH3 CH3-C6H4-COOAl2Cl5 + HCl. The adduct OCO:Al2Cl6 was estimated by monitoring the peak at 1662 cm(-1) in the FTIR spectra. The k values for the Friedel-Crafts reaction was found to be 2.28 X 10(-9) mol(-2) h(-1), which is much lower than that for the reactions involved in the incubation method, viz., 5.4 x 10(-5) and 1.9 X 10(-3) mol(-1) h(-1), respectively. Delta E, Delta G, Delta S, Delta H, and the Arrhenius constant (A) have been calculated for the above reactions. Comparison shows that the incubation method is faster than the Friedel-Crafts reaction. However, both the reactions follow first order kinetics with respect to each of the reactants.