Synthesis, characterization and thermal decomposition of di-(2,4,6-trimethylanilinium) sulphate

Abstract

Di-(2,4,6-trimethylanilinium) sulphate [2,4,6-TMAS] was synthesized by reaction of 2,4,6-trimethylaniline with concentrated sulphuric acid at room temperature. The crystal structure of this salt was determined using single crystal X-ray diffraction. It crystallizes in orthorhombic space group Pna2₁, <i style="">a</i>= 7.7115(1) Å, <i style="">b</i>= 30.3746 (6) Å, <i style="">c</i>=16.9251 (3)Å , <img src='/image/spc_char/alpha.gif' border=0>=<img src='/image/spc_char/beta.gif' border=0>=<img src='/image/spc_char/gamma.gif' border=0>[°]=90°, <i style="">V</i>=3964.43 (12)A and <i style="">Z</i>=8. The structure contains 2,4,6-trimethylanilinium ions that share vertices through intermolecular H- bonds with sulphate ions and a water molecule. Notably thermal and microwave heatings of di-(2,4,6-TMA)S have afforded 3-amino-2,4,6-trimethylbenzenesulphonic acid (3-A-2,4,6-TMBSA) with release of a molecule of amine and water. It has been suggested that the proton transfer from anilinium to SO₄^2-ion is a primary and rate controlling step. Further di-(2,4,6-TMA)S and 3-A-2,4,6-TMBSA were characterized by infrared, mass spectrometry, elemental and thermogravimetric- differential scanning calorimetric (TG-DSC) analyses. The mean value for the energy of activation (83.0 kJ mol^-1) for the conversion of di-(2,4,6-TMA)S to 3-A-2,4,6-TMBSA has been determined from isothermal thermogravimetry data.