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NMR Studies of Solvent Effect on Internal Rotation in Some Non‐Symmetrical 1,2‐Disubstituted Ethanes
Author(s) -
Chen LiShu,
Lin WeiChuwan
Publication year - 1973
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.197300013
Subject(s) - conformational isomerism , chemistry , dielectric , solvent , solvent effects , computational chemistry , crystallography , molecule , organic chemistry , materials science , optoelectronics
The A 2 B 2 system of PMR spectra of 3‐bromopropionic acid, 3‐chloropropionic acid, 3‐bromopropionitrile, and 3‐chloropropionitrile exhibit appreciable solvent effect at room temperature. NMR spectroscopic parameters of A 2 B 2 spectrum as well as physical parameters related to internal rotation, i. e . the highest energy barrier and the energy difference between rotamers, were determined for these compounds in the medium of various solvents. It was found that in the case of 3‐bromopropionic acid, the trans rotamer is more stable than the gauche rotamers, and the energy difference decreases with increasing dielectric constant of solvent. While in the case of 3‐bromopropionitrile, the gauche rotamers were found to be more stable than the trans rotamer and the energy difference increases with increasing dielectric constant of solvent. In the remaining two compounds, 3‐chloropropionic acid and 3‐chloropropionitrile, both trans and gauche rotamers are equally stable in a solvent of low dielectric constant, however in a solvent of higher dielectric constant, the gauche rotamers become more stable than the trans rotamer and the energy difference becomes more pronounced with increasing dielectric constant of solvent.