A theoretical and experimental study on the effect of cationic moiety of quaternary ammonium tribromides in bromination reactions

[Display omitted] •Reaction with CTMATB has lower Gibb’s free energy than with TBATB.•Dissociation enthalpy of CTMATB was found lower than TBATB.•Both methods revealed that CTMATB have an edge over TBATB in bromination reactions. Attempt has been made to explain why different aliphatic quaternary ammonium tribromides (QATBs) show different levels of efficiency in bromination reactions. For this study, tetrabutyl ammonium tribromide (TBATB, [N(C4H9)4]Br3), and cetyl trimethyl ammonium tribromide (CTMATB, [N(CH3)3C16H33]Br3) were used as representative examples. UV–Vis Spectroscopic method was employed to measure the thermodynamic parameters of the reactions. Influence of quaternary ammonium cation on tribromide (Br3−) performance was assessed with the aid of Density Functional Theory (B3LYP/6-311++G(d,p)) by determining the dissociation energy of the QATBs, energies of pairs of their frontier orbitals, which are HOMO and LUMO and calculation of dipole moments.