New insights in the hydrolysis mechanism of carbon disulfide (CS2): a density functional study

Density functional theory (DFT) is used to look into the two-step hydrolysis mechanism of CS2. Through optimizing the structure of reactants, intermediates, transition states, and products, it can be seen that the first step of CS2 is that CS2 reacts with H2O first to form COS intermediate and the second step is COS intermediate reacts with H2O to form H2S and CO2. Hydrogen migration is crucial to the mechanism of CS2 hydrolysis. In the reaction's first step, the rate-determining step in both the single C = S path and the double C = S path possesses a higher barrier of 199.9 kJ/mol; however, the 127.9 kJ/mol barrier in the double C = S path is lower than the 142.8 kJ/mol in the single C = S path. So the double C = S path is better. Similarly, the order of the barriers for the three paths in the second reaction is C = S path < C = S path and C = O path < C = O path. So the C = S path is better. Apart from this, to further explore the reaction of CS2 hydrolysis, the natural bond orbital (NBO) analysis of the transition states was carried out. Besides, to further clarify which reaction path is better, the hydrolysis kinetics of CS2 was analyzed. It was sought out that the hydrolysis of CS2 was an exothermic reaction, and the increment in temperature was adverse to the reaction. During the hydrolysis of CS2, the five reaction paths are parallel and competitive. Our results might contrite to provide a novel method to study the catalytic hydrolysis of CS2.