20 June 2023

The influence of superbasic conditions and solvent effects on NMR spectra and structural parameters of acetylene in solution

Acetylene is a key industrial building block with a reach functionalization chemistry under strong basis (i.e., so called, superbasic) conditions in solution. In spite of significance of such acetylene transformations, mechanistic understanding of liquid-phase processes at molecular level under superbasic conditions remains a challenge. In the present study, a detailed comparative analysis of several factors influencing acetylene in solution was performed using NMR spectroscopy. Solvent effects, deuterium isotope effects, and temperature effects were estimated on experimental JCH spin-spin coupling constants and the chemical shift difference of ??C, and their possible outcome on acetylene bond length were assessed. Acetylene was studied under superbasic conditions in DMSO/KOH mixtures, and chemical exchange processes were observed, manifesting themselves as a coalescence of JCH. Possible exchange reactions are validated by quantum chemical calculations. The studied phenomenon may shed light on the mechanism of acetylene activation under superbasic conditions and contribute to understanding functionalization chemistry in the liquid phase.

Reference: J. Mol. Liq., 2023, 122381.

DOI: 10.1016/j.molliq.2023.122381