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F-19 chemical shifts, coupling constants and conformational preferences in monosubstituted perfluoroparacyclophanes

Texto completo
Autor(es):
Ghiviriga, Ion [1] ; Zhang, Lianhao [1] ; Martinez, Henry [1] ; Contreras, Ruben H. [2, 3] ; Tormena, Claudio F. [4] ; Nodin, Laura [1] ; Dolbier, Jr., William R. [1]
Número total de Autores: 7
Afiliação do(s) autor(es):
[1] Univ Florida, Dept Chem, Gainesville, FL 32611 - USA
[2] Univ Buenos Aires, Fac Ciencias Exactas & Nat, Dept Fis, RA-1428 Buenos Aires, DF - Argentina
[3] IFIBA CONICET, RA-1428 Buenos Aires, DF - Argentina
[4] Univ Estadual Campinas, Inst Chem, Dept Organ Chem, BR-13084971 Sao Paulo - Brazil
Número total de Afiliações: 4
Tipo de documento: Artigo Científico
Fonte: Magnetic Resonance in Chemistry; v. 49, n. 3, p. 93-105, MAR 2011.
Citações Web of Science: 14
Resumo

In the process of studying the chemistry of perfluoro{[}2.2]paracyclophanes (PFPCs), a novel class of compounds, it became necessary to identify some disubstituted products. To achieve this goal, we characterize in this work some monosubstituted PFPCs, identifying their (19)F-(19)F coupling patterns, and establishing a methodology for the assignment of their (19)F chemical shifts. The pattern of coupling constants indicates a skewed geometry in which the upper deck moves towards or away from the substituent, depending on the substituent electron-donor character and size. Quantum chemical calculations, performed at the HF/6-311 + G(d,p)//B3LYP/EPR-III level of theory, confirmed the conformations inferred from coupling constants and reproduced well the values of the couplings. Transmission mechanisms for the FC term of four- and five-bond (19)F-(19)F couplings are discussed in detail. Understanding the conformational preferences of PFPCs and how they are reflected by the coupling constants facilitates the assignment of (19)F chemical shifts in monosubstituted PFPCs and the identification of the disubstituted products. Copyright (C) 2011 John Wiley \& Sons, Ltd. (AU)

Processo FAPESP: 08/06282-0 - Estudo do mecanismo de transmissão de constantes de acoplamento escalar envolvendo o átomo de flúor
Beneficiário:Roberto Rittner Neto
Linha de fomento: Auxílio à Pesquisa - Regular
Processo FAPESP: 06/03980-2 - Interacoes de orbitais e seus efeitos nas constantes de acoplamento escalar em rmn: estudo experimental e teorico.
Beneficiário:Claudio Francisco Tormena
Linha de fomento: Auxílio à Pesquisa - Regular