4-(Dimethylamino)pyridinium chlorosulfonate: A new ionic liquid exhibiting chlorosulfonic acid action as monoprotic Bronsted acid and no sulfonating reagent

• Main Authors: Zaharani, Lia, Johan, Mohd Rafie, Titinchi, Salam, Khaligh, Nader Ghaffari
• Format: Article
• Published: Elsevier 2022
• Subjects: QC Physics; QD Chemistry
• Online Access: http://eprints.um.edu.my/33656/
• Institution: Universiti Malaya

Many papers considered chlorosulfonic acid as a sulfonating and sulfating agent, whereas our previous work and a few reports showed it acts as a monoprotic Bronsted acid. Therefore, in the present work, we decided to respond to this question by investigating the reaction between chlorosulfonic acid and DMAP. First, a new ionic liquid viz. 4-dimethylaminopyridinium chlorosulfonate was obtained, which its chemical structure was elucidated using different spectroscopic techniques. Another derivative, 4-dimethylaminopyridinium hydrogen sulfate, was also synthesized, which showed a similar NMR pattern. The NMR spectra analyses of reactants, the new ionic liquid, and 4-dimethylaminopyridinium hydrogen sulfate support the formation of 4-dimethylaminopyridinium chlorosulfonate. Therefore, the formation of N-sulfonic acid-4-dimethylaminopyridinium chloride or 4-dimethylaminopyridinium sulfate and the presence of an excess of chlorosulfonic acid and sulfuric acid were ruled out based on the spectroscopic results. Finally, the new ionic liquid's thermal behavior and thermal stability were investigated, and a possible mechanism was presented for its degradation based on a TGA/DTA analysis. (C) 2021 Elsevier B.V. All rights reserved.