Benzylic coupling constants in toluene derivatives by J doubling in the frequency domain and DFT calculations

• Published in: Magnetic resonance in chemistry 2009-05, Vol.47 (5), p.437-442
• Main Authors: Pérez-Hernández, Nury, Álvarez-Cisneros, Celina, Cerda-García-Rojas, Carlos M., Morales-Ríos, Martha S., Joseph-Nathan, Pedro
• Format: Article
• Language: English
• Subjects: Algorithms; Benzylic coupling constants; Data Interpretation, Statistical; DFT calculations; Magnetic Resonance Spectroscopy; modified J doubling method; Molecular Conformation; substituted toluenes; Toluene - analogs & derivatives; Toluene - chemistry
• ISSN: 0749-1581; 1097-458X
• DOI: 10.1002/mrc.2411

The recently modified J doubling in the frequency domain method (MJDFDM) allowed the determination of 4, 5, 6J 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. Copyright © 2009 John Wiley & Sons, Ltd. The modified J doubling in the frequency domain method (MJDFDM) allowed the determination of 4, 5, 6J H, CH 3 in toluene, a series of 4‐mono‐ and 3,5‐disubstituted toluene derivatives, as well as in 4‐picoline. Density functional theory calculation of benzylic coupling constants revealed good agreement between predicted and measured values when the B3LYP/aug‐cc‐pVTZ level of theory was used.