On the Nucleophilic Reactivity of 4,6-Dichloro-5-nitrobenzofuroxan with Some Aliphatic and Aromatic Amines: Selective Nucleophilic Substitution

The reaction rates for the nucleophilic aromatic substitution of 4,6-dichloro-5-nitrobenzofuroxan 1 with eight aliphatic amines (characterized by very different basicities/nucleophilicities) and three anilines have been measured in both methanol and toluene. The obtained rates have been related to the basicity (pK_aH in water and K_b in benzene) or nucleophilicity (N Mayr constants) of the tested amines. The whole of the obtained kinetic data has furnished useful information on the high nucleophilic reactivity of benzofuroxan derivatives, which has been related essentially to two factors: the high electron-drawing ability/power of the condensed furoxan ring and the low aromatic character of the benzofuroxan system.

Theoretical estimation of kinetic parameters for nucleophilic substitution reactions in solution: an application of a solution translational entropy model

The kinetic parameters, such as activation entropy, activation enthalpy, activation free-energy, and reaction rate constant, for a series of nucleophilic substitution (SN) reactions in solution, are investigated using both a solution-phase translational entropy model and an ideal gas-phase translational entropy model. The results obtained from the solution translational entropy model are in excellent agreement with the experimental values, while the overestimation of activation free-energy from the ideal gas-phase translational entropy model is as large as 6.9 kcal mol(-1). For some of the reactions studied, such as and in methanol, and and in aqueous solution, the explicit + implicit model, namely, a cluster-continuum type model, should be employed to account for the strong solvent-solute interactions. In addition, the explicit + implicit models have also been applied to the DMSO-H2O mixtures, which would open up a door to investigate the reactions in a mixed solvent using density functional theory (DFT) methods.