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Tin complexes (BuSnCl3 and Bu2SnCl2) were investigated as catalysts for the methanolysis of soybean oil and the esterification of oleic acid with methanol under several reaction conditions. From this study, it is possible to determine that BuSnCl3 was the most active catalyst for both reactions. Studies using 1H NMR confirm this trend, and the reactions attained yields of 89 and 6% by transesterification, and 100 and 82% by esterification when BuSnCl3 and Bu2SnCl2 were used as catalysts, respectively. The results obtained by 119Sn NMR show that during transesterification or esterification, no significant change in the substituents on Sn was detected for either catalyst, and consequently, both catalysts should act as net Lewis acids. Furthermore, computational studies have rationalized the higher activity exhibited by BuSnCl3 in comparison with Bu2SnCl2 because no HCl release occurred through the protonolysis of the chloro-substituent, as shown by 119Sn NMR studies. |
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