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Application of NMR spectroscopy of chiral association complexes. 12 —rate determination of an intramolecular motion in a free molecule by means of dynamic NMR measurements in the presence of an auxiliary compound
Author(s) -
Küspert Reinhard,
Mannschreck Albrecht
Publication year - 1982
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.1270190103
Subject(s) - intramolecular force , extrapolation , chemistry , molecule , nuclear magnetic resonance spectroscopy , spectroscopy , reaction rate constant , crystallography , stereochemistry , computational chemistry , analytical chemistry (journal) , organic chemistry , kinetics , physics , mathematical analysis , mathematics , quantum mechanics
The rate constants of intramolecular processes can sometimes be measured only in the presence of optically active auxiliary compounds. The problem of obtaining the rate for the free molecule was solved by linear extrapolation of rate constant from the complexed to the uncomplexed molecule (LERCUM). This method is developed theoretically and checked experimentally. 2‐Bromo‐2‐methyl‐1‐(3‐bromo‐2‐methoxy‐4,5,6‐trimethylphenyl)‐1‐propanone has the advantage that rotation about its carhonyl‐to‐aryl bond can be measured both in the presence of (+)−2,2,2‐trifluoro‐1‐phenylethanol as well as in the absence of an auxiliary compound. The novel method of extrapolation is confirmed by the agreement between both results.