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  • Title: Benzylic coupling constants in toluene derivatives by J doubling in the frequency domain and DFT calculations.
    Author: Pérez-Hernández N, Alvarez-Cisneros C, Cerda-García-Rojas CM, Morales-Ríos MS, Joseph-Nathan P.
    Journal: Magn Reson Chem; 2009 May; 47(5):437-42. PubMed ID: 19229891.
    Abstract:
    The recently modified J doubling in the frequency domain method (MJDFDM) allowed the determination of (4, 5, 6)J(H, CH(3) ) in toluene, a series of 4-mono- and 3,5-disubstituted toluene derivatives, as well as in 4-picoline. The methyl and aromatic signals were subjected to successive deconvolution processes, which at the end led to singlet signals and afforded the corresponding coupling constant values with a high degree of accuracy. Density functional theory calculation of benzylic coupling constants by addition of the Fermi contact, the spin-dipole, the diamagnetic spin-orbit, and the paramagnetic spin-orbit terms revealed good agreement between predicted and measured values when the B3LYP/aug-cc-pVTZ level of theory was used. Evaluation of the substituent effect over the coupling constant was made for all studied compounds and some limitations of the methodology were evidenced.
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