Gas-phase reaction of ClO− with CHnCl4-n (n = 0, 1, 2, 3) and CX3H (X = F, Cl and Br): Substituent effect from a comparative study

Abstract

Substituent effects on reactivity are studied using the hybrid B3LYP and BHandHLYP methods of density functional theory with the aug-cc-pVDZ basis set. The chosen testing models includes two very representative reactions in chemical research, the bimolecular nucleophilic substitution (SN2) reaction and the deprotonation reaction, in which the former is represented by ClO− + CHnCl4-n (n = 0, 1, 2, 3), and the latter is based on reactions of ClO− with CX3H (X = F, Cl, and Br). Our theoretical findings suggest that a heavier substituent X in substrate results in a higher activation energy, a slower SN2 reaction, but a faster deprotonation reaction. Those are well confirmed by some presented results from bond orders, second-order perturbative energy E(2), and activation strain model analysis. Moreover, we have further explored the reactivity difference derived from substituent effects in term of the relationships of reactive barrier with the charges transferred and the leaving-bond distance in TSs, respectively, especially the TSs in SN2 reactions. Again, the rate constants at 298–1000 K are also evaluated for the SN2 reactions presented through the transition state theory.