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Proton and carbon‐13 nuclear magnetic resonance studies of substituted pyrimidines. V 13 C, 1 H coupling contsants for some methyl‐ and aminopyrimidines
Author(s) -
Riand Jacques,
Che MarieThérèse
Publication year - 1981
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.1270150105
Subject(s) - coupling constant , ring (chemistry) , chemistry , substituent , proton , spectral line , chemical shift , coupling (piping) , resonance (particle physics) , carbon 13 , computational chemistry , crystallography , stereochemistry , atomic physics , physics , organic chemistry , materials science , particle physics , nuclear physics , quantum mechanics , metallurgy
J ( 13 C 1 H) coupling constants for some methyl‐ and aminopyrimidines have been determined by 13 C NMR. Both the one‐bond and long‐bond and long‐range coupling constants follow general trends which can be summarized in a few simple rules. In particular, the 3 J (C‐i,H) coupling constants between a ring carbon C‐i and the ring protons are larger than the 2 J (C‐i,H) coupling constants. The opposite is observed for the couplings between the ring carbons and the methyl protons: 3 J (C,Me). These general rules are very useful for the assignment of resonances in complex 13 C spectra of pyrimidines and seem to be valid for other 6‐membered aromatic nitrogen heterocycles. Furthermore, the additivity of substituent effects on 1 J (CH) for monosubstituted pyrimidines allows the estimation of 1 J (CH) for polysubstituted pyrimidines with a very good accuracy.