NMR Study of Hydrothermal Reactions of Dichloromethane with and without Alkali

Hydrothermal reactions of considerably concentrated (ca. 1 M; M = mol dm-3) dichloromethane, CH2Cl2, were investigated with and without alkali in the temperature range of 150—300 °C by using batch reactors, such as an autoclave and sealed glass tubes. 1H, 2H, and 13C NMR spectra were taken at room temperature as a function of reaction time to analyze the quenched reactants, intermediates, and products. In the presence of NaOH at 2 M, the complete dechlorination was achieved in 270 min at 250 °C and in 60 min at 300 °C. Such gaseous by-products as CO, CO2, and H2 were generated by the decomposition of the disproportionation product, HCOO-. Without alkali, CH2(OH)2 could be detected by 1H and 13C NMR as an intermediate in the hydrolysis of CH2Cl2, before such Cannizzaro products as methanol and formate ion were formed. The mechanism of the hydrothermal reactions of CH2Cl2 is discussed in terms of the hydrolysis intermediate, CH2(OH)2.