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Dependence of 13 C NMR methoxy substituent chemical shift values on π‐bond orders of fused aromatic compounds
Author(s) -
JosephNathan Pedro,
GarcíaMartínez Cirilo,
MoralesRíos Martha S.
Publication year - 1990
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260280406
Subject(s) - chemistry , substituent , chemical shift , correlation coefficient , aromaticity , carbon 13 nmr , computational chemistry , organic chemistry , medicinal chemistry , molecule , statistics , mathematics
The substituent chemical shift values induced by the methoxy group at the two ortho positions of aromatic compounds which include naphthalenes, quinolines, indoles, coumarins, flavones and benzofurans were linearly correlated with π‐bond orders, affording the equation Δδ ortho ( 13 C) = ‐98.68 P π + 50.38 (correlation coefficient = 0.929; root mean square error = 1.95 ppm) when 40 pairs of values are considered. Elimination of six points corresponding to ring‐junction quaternary carbons improves the correlation coefficient to 0.961 (root mean square error = 1.4 ppm) for the equation Δδ ortho ( 13 C) = ‐126.85 P π + 69.66.