Naslov
Prediction of the kinetic stability of N-alkyl X- pyridinium ions in dichloromethane
(Prediction of the kinetic stability of N-alkyl-X- pyridinium ions in dichloromethane)

Autori
Matić, Mirela ; Denegri, Bernard

Izvornik
Journal of physical organic chemistry (0894-3230) 34 (2021); E4248, 9

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
DFT ; heterolysis ; nucleofugality ; pyridinium ; transition states

Sažetak
Geometries of 20 N-[4, 4´-bis (dimethylamino)benzhydryl]-X-pyridinium ions (DMABh-X-pyridinium ions) and of corresponding heterolytic transition structures have been optimized at the M06-2X/6-311+G(2d, p) level of theory in the presence of the IEFPCM model with dichloromethane as a solvent. Using the optimized geometries, free energies of activation (∆G‡model) for the model heterolysis of the DMABh-X- pyridinium ions in dichloromethane at 20°C have been obtained. A very good correlation between ΔG‡model values for the model heterolysis of five reference DMABh-X-pyridinium ions and literature ΔG‡ values for the heterolysis of the same ions in dichloromethane (r = 0.992) validates the procedure for predicting experimental reactivities of the ions (ΔG‡calc) in dichloromethane. Accordingly, the correlation has been employed to obtain predicted free energies of activation (ΔG‡calc) for heterolyses of other 15 DMABh-X- pyridinium ions in dichloromethane from corresponding ΔG‡model values. The high quality of the whole set of the predicted reactivities is confirmed by a very good correlation plot of log kcalc (obtained from ΔG‡calc) versus σ (r = 0.995). Using the previously established correlation equation log k = sf(Ef + Nf), predicted nucleofugality parameters (Nf calc), which quantitatively describe leaving group abilities, have been determined for various Xpyridines in dichloromethane, and now can be used not only for comparing leaving group abilities of X-pyridines with those of other leaving groups on the existing nucleofugality (Nf) scale but also for estimating the reactivity, that is, the kinetic stability, of diverse N-alkyl-X-pyridinium ions in dichloromethane at 20°C.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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