The quantum chemistry study of the hydrogen sulphide photooxidation process in gas phase was performed using density functional theory at the PBE0 6-311++G(d, p) theory level. It was found new perspective reaction pathways. One of them provides a possibility of partial nitromethane regeneration accompanied by nitroso-methane and water formation from radical product of hydrogen addition to nitromethane. This radical product can be obtained in many reaction stages, including new one leading to formation of new reaction product being atomic sulphur. Analysis of thermodynamic and kinetic parameters at standart laboratory conditions (298.15 K,101325 Pa) showed a high probability for mentioned stages to be performed due to low activation energy and negative gibbs energy. Negative enthalpy causes newly found stages to be exothermic.