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13 C‐ and 1 H‐NMR Shielding Effects in Aliphatic gauche/trans Fragments
Author(s) -
Schneider HansJörg,
Buchheit Ulrich,
Hoppen Volker,
Schmidt Günther
Publication year - 1989
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19891220219
Subject(s) - chemistry , steric effects , cyclohexanes , electromagnetic shielding , shielding effect , substituent , anisotropy , bicyclic molecule , stereochemistry , crystallography , organic chemistry , physics , layer (electronics) , quantum mechanics
On the basis of improved calculation models, of new NMR measurements with bicyclo[2.2.1]heptyl and cyclohexyl compounds, and of literature data it is shown that classical mechanisms of sterically induced charge polarizations, of linear electric field, and of anisotropy effects can account for many substituent‐induced shielding (SIS) differences. The rǒle of steric distortions on α‐and β‐SIS is discussed; bond angle variations generated by a methyl group introduction at C‐α and subsequent hybridization changes are correlated with Cα‐Me SIS values as well as with the eq/ax shielding in cyclohexanes.