Study of Aromatic Nucleophilic Substitution with Amines on Nitrothiophenes in Room-Temperature Ionic Liquids: Are the Different Effects on the Behavior of para-Like and ortho-Like Isomers on Going from Conventional Solvents to Room-Temperature Ionic Liquids Related to Solvation Effects?
information concerning reagent−solvent interactions, the reaction was carried out over the temperature range 293−313 K. The reaction occurs faster in ionic liquids than in conventional solvents (methanol, benzene), a dependence of rate constants on amine concentration similar to that observed in methanol, suggesting a parallel behavior. The above reaction also was studied with 2-bromo-3-nitrothiophene, an
The kinetics of the reactions of some 2-L-5-nitro-3-X-thiophenes with primary and secondary amines in methanol at various temperatures have been studied with the aim of obtaining information about the proximity effects of 3-X ortho-like substituents. The results obtained have shown that for all the substituents considered, except for X = Br, the proximity effects of steric nature are of little relevance
The rate constants of the title reactions have been measured at various amine concentrations. The second-order kinetic constant for the amino substitution increases in a hyperbolic way as a function of the nucleophile concentration. The k3Am/k-1 ratio for each catalysed system is not a monotonic function of the X substituent. This result has been rationalized in the framework of the SB-GA (Specific Base-General Acid) mechanism of base catalysis.