10165-70-5Relevant academic research and scientific papers
Base-Catalyzed Reactions of Triarylmethyl Carbocations with Water
Gandler, Joseph R.
, p. 8218 - 8223 (1985)
The general base catalyzed addition of water to a series of triarylmethyl carbocations has been studied in aqueous solution with a series of substituted quinuclidines as base catalysts.Broensted β values for general base catalysis range from 0.33 for trianisylmethyl carbocation, TAM (pKR(1+)=0.82), to 0.52 for Malachite Green, MG (pKR(1+)=6.94).There is a slight tendency for the β values to decrease with decreasing carbocation stability.The rate constants for the "water"-catalyzed reactions show a large positive deviation (800-fold in the case of Malachite Green) and the rate constants for the hydroxide ion catalyzed reactions a small negative deviation from Broensted plots based on quinuclidine catalysis.These results are consistent with a concerted mechanism for the buffer-catalyzed reactions, a stepwise mechanism that proceeds through an oxonium ion intermediate for the "water"-catalyzed reactions (this mechanism corresponds to an A-1 mechanism in the microscopic reverse direction), and either a concerted or preassociation mechanism for the hydroxide ion catalyzed reactions.The positive deviation of water and the negative deviation of the hydroxide ion from the Broensted relationship are opposite the deviations that are normally observed for these species in related reactions: compared to these related reactions, the pH range where buffer catalysis is strongest is shifted to higher pH values.These results also explain why the early attempts to find general base catalysis of the addition of water to triarylmethyl carbocations with acetate buffers proved unsuccessful.
CONDITIONS FOR THE APPLICATION OF ELECTROSTATIC THEORY TO THE KINETICS OF THE REACTIONS OF CONJUGATED CARBONIUM IONS WITH ANIONS IN MIXED AQUENOUS ORGANIC SOLVENTS
Sinev, V. V.,Nikolova, T. A.
, p. 528 - 530 (2007/10/02)
On the basis of an analysis of data on the kinetics of the reaction of conjugated cations of the triarylmethane series with various anions in mixed aquenous organic solvents it was shown that the deviations from electrostatic theory observed for the kinetics of the reactions of cationic substrates with OH- anion are due to transsolvation of the reaction center and to competition from the relay mechanism of transfer of the hydroxide ion with direct nucleophilic displacement of the water from the hydrate shell of the cation.
