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 ΔGf0 (kJ/mol), standard molar enthalpy change of molecular formation ΔHf0 (kJ/mol) and standard molar entropy of molecule S0 (J/mol·K). From these thermodynamics parameters the vibrational modes can be calculated using TG= ΔGf0/S0 and TH= ΔHf0/S0 (in K) as ‘apparent’ temperatures. After equation of thermal energy kTG and kTH (where k is Boltzmann constant) to energy of electromagnetic quanta hfG and hfH (where f is frequency in Hz), it can calculate the wavenumbers (in cm -1) of vibrational modes as: kTG/ch and kTH/ch (where c is the speed of light and h is the Planck constant).