Proton nuclear magnetic resonance spectra of free and hydrogen-bonded thiocyanic, cyanic, and hydrazoic acids

Abstract

The ¹H n.m.r. spectra of dilute carbon tetrachloride solutions of HNCS, HNCO, and HN₃ are reported. The NH signals occur at τ 5·05, 6·65, and 5·90, respectively. The HNCO resonance is a triplet (J 64 Hz) while those for HNCS and HN₃ are broad singlets. The chemical shifts on hydrogen bonding to a selection of Lewis bases are examined in relation to the enthalpy of association, ΔH, and the change in the N–H stretching frequency, Δv. Individual correlations for the three acids can be distinguished. These are discussed in terms of the anisotropic shieldings caused by the NXY moiety, and of the changes in these on hydrogen bonding.