Deuteration kinetics of N‐methylacetamide by means of a stopped‐flow multi‐detector Raman spectrophotometry

Abstract

AbstractN‐methylacetamide dissolved in 1H2O was rapidly mixed with 2H2O by the use of a stopped‐flow device, and Raman spectra of the mixed solution were observed at various times in the course of the deuteration reaction by the use of a multi‐detector system. With continuous wave excitation (Ar+ laser), the time‐resolution reached by our present setup was about 50 ms. The molecular association of N‐methylacetamide in H2O was found to cause a low‐frequency shift of the amide III Raman band at 1317 cm−1 by 9 cm−1. The effect of this association upon the deuteration rate, however, was not found to be appreciable. At 25°C, the rate constants were determined to be 0.067, 0.14, 0.20, 0.41, and 0.63 s−1 at pH = 6.43, 6.87, 7.15, 7.39, and 7.43, respectively.