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Type: Artigo de periódico
Title: Heavy Halogen Atom Effect on C-13 NMR Chemical Shifts in Monohalo Derivatives of Cyclohexane and Pyran. Experimental and Theoretical Study
Author: Neto, AC
Ducati, LC
Rittner, R
Tormena, CF
Contreras, RH
Frenking, G
Abstract: As a first step, a qualitative analysis of the spin-orbit operator was performed to predict the kind of organic compounds, where it could be expected that the SO/FC (spin-orbit/Fermi contact) and SO/SD (spin-orbit/spin dipolar) yield unusually small contributions to the "heavy atom effect" on C-13 SCSs (substituent chemical shifts). This analysis led to the conclusion that compounds presenting strong hyperconjugative interactions involving the sigma(star)(c-x) orbital (X = halogen) are good examples where such effects can be expected to take place. On the basis of such results, the following set of model compounds was chosen: 2-eq-halocyclohexane (2-eq), 2-ax-halocyclohexane (2-ax), and 2-ax-halopyran (3), to measure C-13 SCSs. Such experimental values, as well as those of methane and halomethanes taken from the literature, were compared to calculated values at a nonrelativistic approach using B3LYP, and at a relativistic approach with BP86 using scalar ZORA, spin-orbit ZORA, scalar PAULI, and spin-orbit PAULI. Results from relativistic calculations are in agreement with the trends predicted by the qualitative model discussed in this work.
Country: EUA
Editor: Amer Chemical Soc
Citation: Journal Of Chemical Theory And Computation. Amer Chemical Soc, v. 5, n. 9, n. 2222, n. 2228, 2009.
Rights: fechado
Identifier DOI: 10.1021/ct800520w
Date Issue: 2009
Appears in Collections:Unicamp - Artigos e Outros Documentos

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