This document describes Thermodynamic formulation of activated complex theory, Lindemann – Hinshelwood mechanism of unimolecular reactions. London- Eyring-Polanyi method of calculation of energy of activation. Application of activated complex theory of reaction rates. Temperature dependence of pre-exponential factor. Thermodynamic aspects of reaction rates. Unimolecular reactions and its validity Thermodynamic formulation of activated complex theory, Lindemann – Hinshelwood mechanism of unimolecular reactions. London- Eyring-Polanyi method of calculation of energy of activation. Application of activated complex theory of reaction rates. Temperature dependence of pre-exponentialfactor. Thermodynamic aspects of re