91787-13-2Relevant academic research and scientific papers
Kinetics and Mechanisms of Nucleophilic Displacements whit Heterocycles as Leaving Groups. Part 15. Dependence of Mechanism of Solvolysis of Pyridinium Cations on Solvent Character: Evidence from Rates,p* Values, and Product Analysis
Katritzky, Alan R.,Lopez-Rodriguez, Maria L.,Marquet, Jorge
, p. 349 - 354 (2007/10/02)
p* Values are reported for solvolyses of a series of 1-(s-alkyl)pyridinium cations in 2,2,2-trifluoroethanol or 1,1,1,3,3,3-hexafluoropropan-2-ol as solvents in the absence of nucleophiles.The corresponding reactions with pyridine, piperidine, or morpholine as nucleophile in chloroform, acetonitrile, 2,2,2-trifluoroethanol, or 1,1,1,3,3,3-hexafluoropropan-2-ol are kinetically first-order (independent of nucleophile concentration);these allow p* to be calculated. p* Values correlate with solvent ET values except for pentanol and acetic acid, in which cases they are smaller than expected.Product analysis discloses rearrangement products (derived by hydride shifts) only for solvolysis in non-nucleophilic solvents (trifluoroacetic acid and 1,1,1,3,3,3-hexafluoropropan-2-ol) in the absence of added nucleophilic solvents.The results are interpreted in terms of (a) solvent-assisted solvolysis in nucleophilic solvents, (b) SN1 cleavage of the C-N bond in the rate-determining step both for the unimolecular reactions in the presence of external nucleophiles, and for solvolysis in 2,2,2-trifluoroethanol, and (c) rate-determining ion-molecule pair dissociation for solvolysis in trifluoroacetic acid or 1,1,1,3,3,3-hexafluoropropan-2-ol.
