Theoretical Models and Experimental Data for Reactions between Water and Protonated Alcohols: Substitution and Elimination Mechanisms

Unusual atmospheric pressure chemical ionization conditions for detection of organic peroxides

“…Consistent with many studies reported previously, such behavior could be induced by an elongation of the peroxide O δ+ —C bond and driven by a carbocation stabilization which will decrease the energy level of the transition state of the reaction 21–33. Prior to dissociation, this activated ion undergoes isomerization into an ion–neutral complex which evolves towards two possible a and b pathways (Scheme ) 34. This ion–dipole complex can dissociate by losing the neutral characterized by the lower gas‐phase basicity and releasing protonated species 18, 19, 35, 36.…”

Asymmetric identity SN2 transition states: Nucleophilic substitution at α-substituted carbon and silicon centers

“…Although not identical, this asynchronicity in the flipping of the groups that make op the inverting [C(CH 3 ) 2 (CH 2 X)] "umbrella" is reminiscent of the the truly stepwise Walden inversion that has been found before for anionic S N 2@P reactions at four-coordinated phosphorus [46] as well as in the case of cationic S N 2@C reactions between water and protonated t-butyl alcohol [47]. We feel that this is a fundamental aspect of nucleophilic substitution that may be encountered in many other situations involving more complex reactants, also in cases where these S N 2 reactions are competitive with alternative reaction channels, at variance with the situation in our simple model systems.…”

The Rates of SN2 Reactions and Their Relation to Molecular and Solvent Properties

“…The transition-state bond lengths given by Equation (4) with a' = 0.182 are compared in Figure 1 with the corresponding values obtained by high-level ab initio calculations for symmetrical methyl transfers, in which X = F, Cl, Br or I. [20,28] There is a good agreement between ISM and ab initio calculations. We do not assign a special meaning to the fact that the scaling factor previously employed for atom and proton transfers also works for S N 2 reactions, but it is a remarkable achievement that Equation (3) provides meaningful transition-state bond lengths for such diverse reactions with such a simple scaling factor.…”

“…Comparison between the ISM and ab initio transition-state bond lengths of symmetrical methyl exchanges in the gas phase (*) and of H À + H 2 exchange (&). The ab initio data were taken from refs [28,20,42]…”