The present dissertation entitled “Theoretical study of structure, dissociation, reaction and thermochemistry of molecules of environmental and industrial interest” is submitted to fulfill the requirements for the degree of Doctor of Philosophy (Science) of Jadavpur University. The study has been done for the investigation of electronic structure, metal ligand coordination, potential energy surface of reaction and thermochemistry of molecules having environmental and industrial interest using high-level theoretical methods. This thesis contains five chapters. An introduction of the thesis is given in first chapter for understanding the environment and industrial chemistry. The second chapter describes briefly the computational science, computational chemistry and a review of the theoretical methods. Third chapter deals with the electronic structure and metal ligand coordination observed in some chelates. The fourth chapter gives a theoretical account of the study of the reaction mechanism of an interesting atmospheric reaction. The dissociation channels, thermochemistry and spectroscopy of some molecules of industrial and atmospheric interest are studied in detail in last chapter five. ; The research was carried out under supervision of Prof. Abhijit Kr. Das of the Spectroscopy division of the SPS [School of Physical Sciences]