Thermodynamic nitration rates of aromatic compounds. Part 2. Linear description of rate profiles for the nitration of aromatic compounds in the range 40–98 wt% sulphuric acid

Abstract

New studies of nitration in sulphuric acid have been made at high acidities (80–98 wt% H₂SO₄) where at 90 wt% a maximum occurs in the observed rate constant for aromatic compounds. A new treatment of experimental data is reported which takes into account the effective concentration of solutes and changes in the f_Arf_NO2+/f ratio with acidity, using the M_c function. Compounds nitrating at low and high acidity are tested, and representative examples of the results obtained are given. Experimental evidence points to two significant findings in this study. The variation in the observed rate constants below and above 90 wt% H₂SO₄ is related to ionization of nitric acid to give NO₂⁺ ions. The new procedure applied to the kinetic data allows us to obtain a linear description of rate profiles for substrates reacting as free bases in the range 40–98 wt% H₂SO₄.