NMR chemical shift temperature dependence of isocyanomethane

Abstract

We have measured the temperature dependence of the 1H, 13C and 14N isotropic chemical shifts for isocyanomethane, C 2H 3NC 1, both as a neat liquid and in dilute liquid solution with ethanol/ethylene glycol. In both samples, the hydrogen chemical shielding is essentially independent of temperature; the terminal carbon atom becomes more shielded, and the nitrogen and methyl carbon atoms become less shielded with decreasing temperature. The apparent solvent-induced chemical shift changes are −0.57, −1.20, −1.24 and −2.03 ppm for 1H, 14N, 13C 2 and 13C 1, respectively, compared with the neat liquid. We discuss and compare the temperature dependencies for the nitrogen chemical shift and quadrupole coupling parameter. The nuclear spin–spin coupling parameters were measured at high and low temperatures for both samples. J NC 1 shows a definite solvent dependence, and a possible temperature dependence in the neat liquid. Any possible solvent or temperature dependencies for the other spin–spin coupling parameters are within experimental uncertainty.