Intermolecular effects on 1H, 13C, and 15N nuclear magnetic shielding in HCN

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Abstract
We have observed the temperature dependence of the 1H, 13C, and 15N NMR spectra in HCN in the liquid phase and also in the saturated vapor. Concentrations observed include 0.05 to 0.30 mol/l for the vapor and 21–27 mol/l for the liquid at temperatures ranging from 230 up to 380 K. The gas‐to‐liquid shifts and the chemical shift between the dimer and the monomer have been determined for 1H, 13C, and 15N nuclei. A dichotomy in the 15N shifts in nitrogen nuclear environments capable of hydrogen bonding is noted. 15N in HCN appears to be an archetype of nitrogen nuclear environment which is in the same class as pyridine and acetonitrile (and which behaves in a manner opposite to that of 15N in NH3 and saturated amines), such that the effect of intermolecular interactions is to lead to an unusual increase rather than the usual decrease in shielding observed for all other nuclei.