Effect of solvents on regioselectivity of anisole nitration

Department of Chemical Engineering, University of Calcutta, 92, Acharya Prafulla Chandra Road,

Kolkata-700 009, India

E-mail : chhaya_samanta@rediffmail.com, parameswar_de@rediffmail.com, praycuce@rediffmail.com

Fax : 91-33-23519755

Manuscript received online 25 October 2013, accepted 13 February 2014

Nitration of anisole dissolved in different solvents with 70% (w/v) nitric acid was studied. Solvents were observed to strongly influence positional selectivity and rate of nitration. The ortho/para ratio remained virtually constant (~1.2) in nonpolar solvents, but varied considerably with polar solvents. It appeared to have a linear correlation with the ratio of solubility of water in solvent to dielectric constant. Conversion also seemed to be linearly correlated with inverse of solubility of water. Reactions were found to occur in both organic and aqueous phases. In general, better conversions and yields were obtained in nonpolar solvents. The order of preference is : n-heptane > cyclohexane > n-hexane > carbon tetrachloride. The process is also environment friendly.