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19 F chemical shifts, coupling constants and conformational preferences in monosubstituted perfluoroparacyclophanes
Author(s) -
Ghiviriga Ion,
Zhang Lianhao,
Martinez Henry,
Contreras Rubén H.,
Tormena Cláudio F.,
Nodin Laura,
Dolbier William R.
Publication year - 2011
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.2713
Subject(s) - chemistry , coupling constant , chemical shift , computational chemistry , coupling (piping) , stereochemistry , quantum mechanics , physics , mechanical engineering , engineering
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 © 2011 John Wiley & Sons, Ltd.