Theoretical study of Gibbs free energy and NMR chemical shifts, of the effect of methyl substituents on the isomers of (E)-1-(α,Ꞵ-Dimethylbenzyliden)-2,2-diphenylhydrazine
| Autor: | JUAN CARLOS RAMÍREZ-GARCÍA, RICARDO VÁZQUEZ-RAMÍREZ, MARÍA EUGENIA PATIÑO, CARLA AGUIRRE-CABRERA, VLADIMIR CARRANZA, CARMEN MÁRIA GONZÁLEZ ÁLVAREZ |
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| Jazyk: | angličtina |
| Rok vydání: | 2023 |
| Předmět: | |
| Zdroj: | Anais da Academia Brasileira de Ciências, Vol 95, Iss suppl 1 (2023) |
| Druh dokumentu: | article |
| ISSN: | 1678-2690 0001-3765 |
| DOI: | 10.1590/0001-3765202320220766 |
| Popis: | Abstract A theoretical analysis of free Gibbs Energy and NMR 1H 13C chemical shifts of the effect of introduce methyl groups on diphenyl rings, to produce different isomers of (E)-1-(α,Ꞵ-dimethylbenzylidene)-2,2-diphenylhydrazine, is presented. IR vibrational frequencies, Mulliken charges, molecular electrostatic potential (MEP), Gibbs free energy (G) and 1H- and 13C-NMR chemical shifts were obtained by theoretical calculations. In this analysis it was found that the position of the methyl group affects the values of the 1H- and 13C-NMR chemical shifts and the ∆G and ∆H thermodynamic properties of formation and reaction, these properties vary with the same trend, for the isomers studied. Gibbs free energy calculations show that the theoretical (E)-1-(3,4-Dimethylbenzylidene)-2,2-diphenylhydrazine isomer is the most stable, which explains the success of the experimental synthesis of this compound among the other isomers. For this molecule, the C of the HC=N group is the most nucleophilic and the H is the least acidic. The 1H-NMR chemical shifts of protons show a strong correlation with the C=N distance. It was also observed that methyl affects the ν(C=N) frequencies, the C=N distance increases when the inductive effect of the methyl groups is in the structure. |
| Databáze: | Directory of Open Access Journals |
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