Quantum chemical calculation of the interaction between unsymmetrical dimethylhydrazine and water molecules

Water content is one of the key factors affecting the quality of unsymmetrical dimethylhydrazine(1,1-Dimethylhydrazine, UDMH). In this paper, Quantum chemical calculations were employed to investigate the critical mechanisms of the long-term interaction between UDMH and water. They form weak hydrogen bonds with an energy of approximately 3.8 kcal/mol⁓4.8 kcal/mol. Under standard conditions, the Gibbs free energy barrier for hydration reaction is 20.05 kcal/mol, and Gibbs free energy change is 4.22 kcal/mol. The hydration reaction is highly likely to occur, and these findings have important implications for the management of trace water content during the storage of UDMH. • UDMH and water form a weak hydrongen bond which is easily broken and difficult to form. • UDMH tends to undergo hydration reaction with water, and the influence of trace water on UDMH cannot be ignored during long-term storage. • Increasing the purity of nitrogen gas or reducing the dew point of nitrogen gas to improve the safety and quality of long-term storage of UDMH.