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Proton magnetic resonance study of rotational isomerism in vinylcycloalkanes
Author(s) -
De Maré George R.,
Lapaille Serge
Publication year - 1980
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270130116
Subject(s) - conformational isomerism , vicinal , chemistry , proton , coupling constant , proton magnetic resonance , molecule , solvent , nuclear magnetic resonance , ring (chemistry) , crystallography , proton spin crisis , resonance (particle physics) , atomic physics , physics , organic chemistry , nuclear physics , particle physics
The vicinal coupling constant, J (12), between the vinyl CH and the ring CH protons in vinylcyclohexane was calculated from a ‘partial molecule’ six‐spin system. The 100 and 270 MHz results are in good agreement; those at 60 MHz were, however, still inaccurate in this approximation. J (12) increases with increasing solvent polarity and decreasing temperature. The energy difference between the s‐ trans and gauche conformers in both C 2 Cl 4 and perdeuterioacetone solvents is 879 ± 167 J mol −1 (210±40 cal mole −1 ). The s‐ trans conformer is the most stable, in contrast to the isoelectronic cyclohexylcarboxyaldehyde where the gauche rotamers are lower in energy.