INVESTIGATION ON THE THERMOCHEMISTRY, MOLECULAR SPECTROSCOPY AND STRUCTURAL PARAMETERS OF PYRROLE AND ITS ISOMERS: A QUANTUM CHEMISTRY APPROACH

Abstract

The isomers of C4H5N consisting of eleven members (2-vinyl-2H-azirene, Isocyanocyclopropane, Ally isocyanide, N-vinylethyleneimine, Cyanocyclopropane, 2H-pyrrole, 3H-pyrrole, Ally cyanide, 2-cyanopropene, 2-butenenitrile, Pyrrole) have been studied computationally using the Gaussian-4 (G4) compound model with the Gaussian 09 suite of programs. Quantum chemical parameters such as standard enthalpy of formation, vibrational frequencies, rotational constants, bond distance and angle, and dipole moment were obtained and compared with experimental values (where available). Pyrrole was predicted to be the most stable among the C4H5N isomers with the least standard enthalpy of formation of 24.1kcal/mol. The calculated bond distances and angles for pyrrole were observed to be in excellent agreement with the measured experimental values. Also, the calculated rotational constants (A= 9.1392127, B=9.0066121, C=4.5362140) and dipole moment (1.8628D) for pyrrole were accurately predicted when compared to the experimentally determined values. Thus, the high accuracy obtained from this quantum chemical calculation indicates that other isomers of C4H5N with no experimental values are well predicted with the Gaussian-4G4 compound model.