Some empirical correlations between the thermodynamic properties of hydrogen cyanide, water and acetylene molecules and their infrared spectra

Abstract

A new method for calculating vibrational modes in the infrared region of the spectrum is proposed. The method is based on the thermodynamic parameters of the molecules-standard molar Gibbs free energy change of molecular formation ΔG f 0 (kJ/mol), standard molar enthalpy change of molecular formation ΔH f 0 (kJ/mol) and standard molar entropy of molecule S 0 (J/mol·K). From these thermodynamics parameters the vibrational modes can be calculated using T G = ΔG f 0 /S 0 and T H = ΔH f 0 /S 0 (in K) as 'apparent' temperatures. After equation of thermal energy kT G and kT H (where k is Boltzmann constant) to energy of electromagnetic quanta hf G and hf H (where f is frequency in Hz), it can calculate the wavenumbers (in cm -1 ) of vibrational modes as: kT G /ch and kT H /ch (where c is the speed of light and h is the Planck constant).