Naslov
DFT‐PCM Study on Solvolytic Behaviour of N‐alkyl‐X‐ pyridinium Ions

Autori
Matić, Mirela ; Denegri, Bernard

Izvornik
ChemistrySelect (2365-6549) 6 (2021), 9; 2410-2423

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

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

Sažetak
Using the M06-2X method and IEFPCM for ethanol, geometries of various N-benzhydryl-X-pyridinium ions and corresponding heterolytic transition structures have been optimized to calculate free energies of activation (ΔG ‡model) for the model heterolysis of the ions at 25 °C. Very good correlations between ΔG ‡model values and corresponding measured ΔG ‡ values have made it possible to estimate reliable reactivities of N- (4, 4'-dimethoxybenzhydryl)-X-pyridinium ions in protic solvents as well as nucleofugality parameters (Nf calc) for 18 X-substituted pyridines. Computational results further reveal that geometric progression along the heterolytic reaction coordinate is synchronized with ionic charge transfer. A Leffler–Hammond coefficient of 0.65 (× 100%) corresponds to both the amount of the ionic charge transferred from the X-pyridine moiety to the alkyl electrofuge (65-67%) and the extent of geometric progression (64%) on proceeding from the ionic substrate to TS in the thermoneutral heterolysis. Consequently, exergonic heterolyses of very reactive N-alkyl-X-pyridinium ions proceed through the geometrically late transition states.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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