NMR study of hydrothermal reactions of dichloromethane with and without alkali

Article abstract of DOI:10.1246/bcsj.73.2687

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.