Synthesis and characterization of two new molten acid salts: Safe and greener alternatives to sulfuric acid for the hydrolytic conversion of 1,1,1,3-tetrachloro-3-phenylpropane to cinnamic acid

• Main Authors: Zaharani, Lia, Gorjian, Hayedeh, Johan, Mohd Rafie, Khaligh, Nader Ghaffari
• Format: Article
• Published: Elsevier 2021
• Subjects: Q Science (General)
• Online Access: http://eprints.um.edu.my/26077/; https://doi.org/10.1016/j.molstruc.2021.130977

Available online Two new acid salts were synthesized, and their chemical structures were characterized by various spectra data analyses. Although 1H NMR did not show acid proton of [HSO4]−, the FTIR spectra of molten acid salts act as key support to approve of their chemical structures. The structure elucidation of the molten acid salts demonstrated the existence of 4,4ʹ-trimethylene-N,Nʹ-dipiperidinium dication with sulfate and hydrogen sulfate anion(s). Thus, sulfuric acid can act as a diprotic or monoprotic Brönsted acid when it is treated by a secondary amine regarding the initial mole ratio of sulfuric acid and amine. Also, the catalytic activity of these molten acid salts was investigated for the hydrolytic conversion of (1,3,3,3-tetrachloropropyl)benzene to cinnamic acid. The desired product was obtained in 88 ± 2.0% yield under optimal conditions. The molten acid salts were high recyclable and their chemical structure and catalytic efficiency showed no significant change even after the 5th run. Furthermore, TMDP-SA (1:1) showed a much weaker corrosive property compared with TMDP-SA (1:2) and SA (98%), and the surface of stainless steel was intact even after 24 h. This fact and the acidity of two molten acid salts also confirm the proposed chemical structures. © 2021 Elsevier B.V.