A theoretical study of the kinetics and mechanism of the cyclization of citronellal in the gas phase was performed using density functional theory methods at the B3LYP level of theory with 6-311G, 6-311G*, 6-31G**, 6-311G**, 6-311+G and 6-311++G basis sets at 298.15 K, 433.15 K, and 473.15 K. Equilibrium molecular geometries and harmonic vibrational frequencies of the reactant, transition state and products were calculated. Rate constants and activation thermodynamic parameters were calculated and showed a fairly good agreement with experimental results. The effect of solvent polarity on the reaction was studied. These calculations indicated that the reaction proceeds through an asynchronous concerted mechanism.
