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|Type:||Artigo de periódico|
|Title:||F-19 chemical shifts, coupling constants and conformational preferences in monosubstituted perfluoroparacyclophanes|
|Abstract:||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 F-19-F-19 coupling patterns, and establishing a methodology for the assignment of their F-19 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 F-19-F-19 couplings are discussed in detail. Understanding the conformational preferences of PFPCs and how they are reflected by the coupling constants facilitates the assignment of F-19 chemical shifts in monosubstituted PFPCs and the identification of the disubstituted products. Copyright (C) 2011 John Wiley & Sons, Ltd.|
F-19 chemical shifts
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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