A dipole moment puzzle

• Published in: Canadian journal of chemistry Vol. 98; no. 10; pp. 616 - 622
• Main Authors: Barón, Máximo, Stewart, James J.P
• Format: Journal Article
• Language: English
• Published: 1840 Woodward Drive, Suite 1, Ottawa, ON K2C 0P7 NRC Research Press 01.10.2020; Canadian Science Publishing NRC Research Press
• Subjects: 1,4-disubstituted and tetrasubstituted cyclohexanes; cyclohexanes 1,4-disubsitués et tétrasubstitués; Dipole moments; dipole moments semiempirical method; intrinsic reaction coordinates energetics and dipole moments; modèles fiables de chimie computationnelle; méthode semi-empirique de calcul des moments dipolaires; NMR; Nuclear magnetic resonance; PM7; proton equivalence; Protons; reliable computation chemistry; Stewart, James J.P; énergétique des coordonnées de réaction et moments dipolaires intrinsèques; équivalence de proton
• ISSN: 0008-4042; 1480-3291
• DOI: 10.1139/cjc-2020-0020

The centrosymmetric compound trans-1,4-dibromo-1,4-dicyanocyclohexane is unusual in that, although it would be expected to have a zero dipole moment, and this has been verified in the crystal, it has also been observed to have a significantly nonzero dipole when in solution. In addition, using NMR, ring protons that were expected to be magnetically inequivalent were found to be equivalent. An answer to these two puzzles has been found by computationally modeling its behavior when unconstrained by crystal forces.