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Internal rotation of CH 3 groups and entropy difference between diastereoisomers: A 13 C NMR study via relaxation time measurements
Author(s) -
Brunel Y.,
Coulombeau C.,
Lavaitte S.,
Reisse J.
Publication year - 1991
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610040208
Subject(s) - chemistry , intramolecular force , intermolecular force , internal rotation , relaxation (psychology) , nuclear magnetic resonance , rotational diffusion , diastereomer , entropy (arrow of time) , entropy of activation , enthalpy , rotation (mathematics) , analytical chemistry (journal) , molecular physics , thermodynamics , molecule , stereochemistry , kinetics , reaction rate constant , organic chemistry , physics , mechanical engineering , psychology , social psychology , geometry , mathematics , engineering , quantum mechanics
Overall and internal rotation can be studied by means of relaxation time measurements on carbon‐13. Diffusion constants associated with overall rotation and internal rotation can be used to quantify the intermolecular and intramolecular motional constraints. During the course of the study, a very careful examination of monomethyl and dimethylnorbornanes was performed and the results were compared with data obtained by neutron inelastic scattering. This study led to a clear conclusion concerning the real usefulness of relaxation time measurements as a very good alternative method for the determination of entropy contributions, which are usually calculated on the basis of vibrational studies.