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Type: Artigo de periódico
Title: Lone-pair orientation effect of an alpha-oxygen atom on (1)J(CC) NMR spin-spin coupling constants in o-substituted phenols. Experimental and DFT study
Author: Taurian, OE
Contreras, RH
De Kowalewski, DG
Perez, JE
Tormena, CF
Abstract: The well-known N lone-pair orientation effect on (1)J(CC) spin-spin coupling constants (SSCCs) in oximes and their derivatives was used to study how negative hyperconjugative interactions of type LP1(O) -> sigma* CC depend on ortho interactions involving the OH group. This study demanded the following analyses: (i) a qualitative estimation of how (1)J(CC) SSCCs are affected by hyperconjugative interactions, ( ii) a study of similar stereochemical effects to those in oximes, but in (1)J(C1C2) and (1)J(C1C6) in a series of 2-substituted phenols, and ( iii) a quantitative estimation, with the natural bond order approach, of some key electron delocalization interactions. A few unexpected results are quoted. LP1(O) -> sigma* cc interactions are affected by proximity interactions as follows: ( a) they are enhanced by hydrogen bonds transferring charge into the (O-H)* antibonding orbital; (b) they are enhanced by proximity interactions of type LP1(O)center dot center dot center dot H-C; (c) they are inhibited by interactions of type LP(O-1)center dot center dot center dot H-O. Consequences of these observations are discussed.
Country: EUA
Editor: Amer Chemical Soc
Rights: fechado
Identifier DOI: 10.1021/ct7000396
Date Issue: 2007
Appears in Collections:Unicamp - Artigos e Outros Documentos

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