Conformational analysis of 2,5‐diaryl‐4‐methyl‐2,4‐dihydro‐3H‐1,2,4‐triazol‐3‐ones: Multinuclear NMR and DFT calculations

Abstract

Conformational exploration of five 2,5‐diaryl‐4‐methyl‐2,4‐dihydro‐3H‐1,2,4‐triazol‐3‐ones has been carried out based on a combination of their NMR chemical shifts determined in CDCl3 and the scrutiny of their computed relative energies and absolute shieldings calculated at the DFT/GIAO/B3LYP/6–311++G(d,p) level. The very flat potential energy curves corresponding to the three relevant single bond rotations were explored by calculating the energy of the rotational barriers and comparing the experimental chemical shifts with those theoretically calculated in each rotamer by statistical analysis.

Nuclear Magnetic Resonance

“…68 As revealed by Gerothanassis, 69 revision of structure of geometric isomers of conjugated linolenic acids, hexadecatrienyl pheromones, and model triene-containing compounds was achieved as a result of close symbiosis between experimental and theoretical NMR approaches. Claramunt et al 70 reported on multinuclear NMR and DFT calculations supporting the conformational analysis of 2,5-diaryl-4-methyl-2,4-dihydro-3H-1,2,4-triazol-3-ones. The loliolide molecule and its isomers were studied theoretically and their nuclear shieldings were predicted.…”

Addition reaction of azoles to acetone‐d6: NMR and computational studies

“…The absolute chemical shieldings have been calculated for the gas phase, while the chemical shifts correspond to values determined in the solution. The chemical shifts taking into account solvent effects were not calculated because if the absolute chemical shieldings were calculated with a general solvent model like the polarizable continuum model (PCM, THF, MeOH, and H 2 O) 18 the results do not improve and in most cases get worse 19 …”