engleski

Nucleofugalities of neutral leaving groups in 80% aqueous acetonitrile

Nucleofugalites of tetrahydrothiofene, dimethylsulfide and pyridine in 80 % aq. acetonitrile have been derived from the SN1 solvolysis rate constants of the corresponding X, Y-benzhydryl derivates (1-10) by applying the LFER equation: log k = sf (Ef + Nf), in which: k is a first-order rate constant for SN1 reaction, sf (slope of the log k/Ef correlation line) and Nf (nucleofugality ; negative intercept on the abscissa) are nucleofuge specific parameters, and Ef is the electofugality parameter. [1] It has been found that the changes of the Nf parameters of neutral leaving groups [2–4] with the solvent composition are in an opposite direction compared to those obtained for anionic leaving groups, [5, 6] i.e. Nf values decrease as the polarity (water content) of the solvent increases. Although, acetonitrile constitutes a polar aprotic solvent and good cation solvatator that has the ability to solvate charged substrates more effeiciently than polar protic solvents in the reactant ground state, relative differences in Nf values of neutral leaving groups are similar as in protic aqueous solvents.

nucleofugality ; neutral leaving groups ; acetonitrile ; LFER equatioon

nije evidentirano