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Intrinsic rotation and molecular structure
Author(s) -
Polavarapu Prasad L.,
Petrovic Ana,
Wang Feng
Publication year - 2003
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.10255
Subject(s) - chemistry , specific rotation , rotation (mathematics) , epichlorohydrin , sign (mathematics) , solvent , molecule , crystallography , computational chemistry , stereochemistry , organic chemistry , geometry , mathematical analysis , mathematics
The intrinsic rotation, limiting value of specific rotation at zero concentration, of (R)‐(–)‐epichlorohydrin was measured in four different solvents, CH 3 OH, CH 2 Cl 2 , CHCl 3 and CCl 4 . It was found that the sign of rotation in CH 3 OH, and CH 2 Cl 2 solvents is opposite to that in CCl 4 . The intrinsic rotation in CHCl 3 is close to zero. This observed pattern was explained using density functional calculations of specific rotation using very large basis sets. It was found that the g‐I and g‐II conformations of epichlorohydrin have nearly the same magnitude of specific rotation but with opposite sign. When these two conformations have equal populations, as in CHCl 3 solvent, the net rotation is close to zero. When g‐II conformation dominates, as in CCl 4 solvent, the observed sign of rotation will be opposite to that when g‐I conformation dominates, as in CH 2 Cl 2 and CH 3 OH solvents. A combination of intrinsic rotation measurement with density functional prediction of specific rotation is demonstrated to be a practical method for determining the structures of molecules. Chirality 15:S143–S149, 2003. © 2003 Wiley‐Liss, Inc.