Pressure-induced proton NMR chemical shift of some simple hydrocarbon molecules in hexane solution. Marked low field shift of ethynyl proton resonance.

Pressure dependence of the ethynyl proton chemical shift of phenylacetylene was studied in comparison with some simple hydrocarbons. The pronounced low field displacement is interpreted taking account of a geometric feature of the ethynyl group, where the terminal hydrogen atom is exposed to a closer contact with solvent molecules.