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High resolution 13 C NMR spectroscopy. IV —stereochemical assignments in butenedioic acids and 3‐pentene‐2‐ones
Author(s) -
Braun S.
Publication year - 1978
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.1270110406
Subject(s) - vicinal , chemistry , steric effects , coupling constant , stereochemistry , chemical shift , double bond , pentene , nuclear magnetic resonance spectroscopy , cis–trans isomerism , medicinal chemistry , computational chemistry , organic chemistry , physics , catalysis , particle physics
Vicinal 13 C, H coupling constants 3 J (CO, H) for butenedioic acids and 3 J (CH 3 , H) for 3‐pentene‐2‐ones have been determined and are correlated with the configuration of the corresponding CC double bond. For both types the relationship 3 J (CH) trans > 3 J (CH) cis holds; in the case of the CH 3 , H couplings, however, the 3 J (CH 3 , H) trans values are reduced because of steric reasons, so that configurational assignments seem possible only when both isomers are present. Additionally, the coupling constants 3 J (CO C H 3 , H ) and the chemical shifts δ CO C H 3have been evaluated for the pentenones and it is shown that these parameters give information about the predominating conformation of α, β‐unsaturated methyl ketones.