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Application of the topological analysis of 13C chemical shifts to the elucidation of the electronic and steric features of polyoxygenated benzenes with different substituents. Simulation of the 13C NMR spectra

✍ Scribed by Valentina I. Dostovalova; Lev A. Fedorov

Publisher
John Wiley and Sons
Year
1992
Tongue
English
Weight
700 KB
Volume
30
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

A novel topological method was developed for the analysis of ^13^C chemical shifts in polyoxygenated benzenes, C~6~H~6‐n~(OY)~n~, where Y = H, Me and Ph. Carbon chemical shifts were described with individual and collective increments for oxygen itself and for oxygen substituents. The oxygens themselves have only one two‐particle increment (1,4‐dioxy interaction) in addition to the individual positional increments (ipso, ortho, meta, para). The 1,2‐dioxy interaction exerts no influence on any ring carbon chemical shifts, and thus the 1,2‐di‐ortho‐subgraphs were connected with the steric properties of the oxygen substituents. The results are in agreement with molecular mechanics calculations and NMR data in the solid state. Hydrogen bonding with specific solvents deshielded the ipso and ortho carbons by about 1.5 ppm. This predictive set completely described the ^13^C NMR spectra of all the polyoxygenated benzenes studied within the experimental accuracy (RRMS = 0.6 ppm). The incremental scheme will be predictive and useful for PC programming.

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