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Principal component analysis in studies of substituent‐induced chemical shifts of 1,4‐disubstituted benzenes
Author(s) -
Canto Eduardo L.,
Tasic Ljubica,
Bruns Roy E.,
Rittner Roberto
Publication year - 2001
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.849
Subject(s) - substituent , chemistry , chemical shift , benzene , principal component analysis , halogen , stereochemistry , medicinal chemistry , computational chemistry , crystallography , organic chemistry , alkyl , artificial intelligence , computer science
Chemometric analyses of 1,4‐disubstituted benzene aromatic carbon atom NMR chemical shifts, bearing 14 substituents (X) within a complete series involving the same substituents as fixed groups (Y), are reported. The substituent effects of (i) strong electron donors (NMe 2 , NH 2 and OMe), (ii) halogens (F, Cl and Br), (iii) electron acceptors (CF 3 , CN and NO 2 ), (iv) acceptors of the carbonyl type [C(O)OEt, C(O)Me and CHO] and (v) neutral groups (H and Me) were studied using principal component analysis (PCA). The charge alterations (Δ q ) induced by introducing a substituent X at C‐1 were also analyzed by the means of PCA of data obtained from theoretical calculations (AM1 method). The correlations among the substituent chemical shifts (SCS) and among the charge alterations (Δ q ) and the dependence of SCS on charge alterations were analyzed by regression analyses applied to the scores of the first principal components (PC1) obtained in the PCA of the SCS and Δ q values. Copyright © 2001 John Wiley & Sons, Ltd.