Ordering of p-n-alkylbenzoic acids (nBAC) having four, five, and six alkyl chain carbon atoms – a computational analysis



A computational analysis of ordering in p-n-alkylbenzoic acids, having 4 (4BAC), 5 (5BAC), and 6 (6BAC) alkyl chain carbon atoms, has been carried out based on quantum mechanics and intermolecular forces. The evaluation of atomic charge and dipole moment at each atomic centre has been carried out through an all-valance electron (CNDO/2) method. The modified Rayleigh-Schrodinger perturbation theory along with multicentered-multipole expansion method has been employed to evaluate long-range intermolecular interactions while a ‘6-exp’ potential function has been assumed for short-range interactions. The total interaction energy values obtained through these computations were used to calculate the probability of each configuration at room temperature, nematic-isotropic transition temperature and above transition temperature using the Maxwell-Boltzmann formula. A comparative picture of molecular parameters like total energy, binding energy and total dipole moment has been given. A model has been developed to describe the nematogenicity of these acids in terms of their relative order with molecular parameter introduced in this article.