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NMR vs. molecular modeling. Part IV—conformational analysis of menthone and isomenthone imines

✍ Scribed by William B. Smith; Carlos A. Amezcua

Publisher
John Wiley and Sons
Year
1999
Tongue
English
Weight
170 KB
Volume
37
Category
Article
ISSN
0749-1581

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✦ Synopsis

The conformational analysis of a series of menthone and isomenthone imines was accomplished by 1HNMR spectroscopy and was compared with molecular modeling computations. The (E) menthone derivatives contain about 20% of a 2,5-diaxial chair conformer at room temperature (22È23 ¡C), whereas in the (E)-and (Z)isomenthone counterparts the major conformer has axial isopropyl and equatorial methyl groups. These peculiar conformations are a consequence of pseudo-allylic A(1,3) interactions between the isopropyl group and the nonbonded pair of electrons of the nitrogen, which dominate the axialÈaxial interactions between the alkyl chains and the protons of the ring in the isomenthone imines and are of considerable importance in the menthone derivatives.

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