Solvent effects on kinetics of an heteroatomic nucleophilic substitution reaction in ionic liquid and molecular solvents mixtures

• Published in: Russian Journal of Physical Chemistry A 2013-12, Vol.87 (12), p.1969-1975
• Main Authors: Salari, Hadi, Pedervand, Mohsen, Sadeghzadeh-Darabi, Faramarz, Gholami, Mohammad Reza
• Format: Article
• Language: English
• Subjects: Chemical Kinetics and Catalysis; Chemistry; Chemistry and Materials Science; Physical Chemistry
• ISSN: 0036-0244; 1531-863X
• DOI: 10.1134/S0036024413120297

Rate constants, k A , for the aromatic nucleophilic substitution reaction of 2-chloro-3,5-dinitropyridine with aniline were determined in different compositions of 2-propanol mixed with hexane, benzene, and 2-methylpropan-2-ol and 1-ethyl-3-methylimidazolium ethylsulfate ([Emim][EtSO 4 ]) with dimethyl sulfoxide at 25°C. The obtained rate constants of the reaction in pure solvents are in the following order: 2-methylpropan-2-ol > dimethyl sulfoxide > 2-propanol > hexane > benzene > [Emim][EtSO 4 ]. Molecularmicroscopic solvent parameters corresponding to the selected binary mixtures were utilized to study the kinetics of a nucleophilic substitution reaction in order to investigate and compare the effects of the solvents on a chemical process. The influence of solvent parameters including normalized polarity ( E T N ), dipolarity/polarizability (π*), hydrogen bond donor acidity (α), and hydrogen bond acceptor basicity (β) on the second-order rate constants were investigated and multiple linear regressions gave much better results with regard to single parameter regressions. The dipolarity/polarizability of media has a positive effect in all mixtures regarding zwitterionic character of the reaction intermediate and the hydrogen bond acceptor basicity of the solvent by stabilizing of activated complex increases the reaction rate.