SO₃H-Functionalized Ionic Liquids for Selective Alkylation of p-Cresol with tert-Butanol

Abstract

The SO3H-functionalized ionic liquids were synthesized by using pyridine and 1,4-butane or 1,3-propane sulfone as the source and characterized by NMR and time-of-flight mass spectrometry. The acidity of the ionic liquids determined by the Hammett method is almost the same as that of a conventional acid, such as H2SO4. The catalytic performance of ionic liquids for the tert-butylation of p-cresol with tert-butanol was evaluated; by using the ionic liquids as catalysts at the optimum reaction conditions, 79% of the p-cresol conversion and 92% of the selectivity to 2-tert-butyl-p-cresol can be obtained. The spent ionic liquid can be recovered and recycled. The possible mechanism for this reaction system was discussed based on the reaction results and the ab initio calculation results.

Long-chain double SO3H-functionalized Brønsted acidic ionic liquids catalyzed selective alkylation of phenol andp-cresol with tert-butanol

“…This indicated that the increase in temperature mainly cause the O-alkylated product turned into 2-TBC and further C-alkylation of 2-TBC with TBA. With the increasing of reaction time, the conversion of p-cresol and the selectivity of 2-TBC increase rapidly and reach a maximum after 6 h. Continued to increase in reaction time, the selectivity of 2,6-DTBC improves gradually, but the conversion of p-cresol almost remains constant, which agrees with the results reported in literature (16,17). The influence of amount of BAILs on the conversion of p-cresol and Green Chemistry Letters and Reviews 181 the selectivity of 2-TBC was also discussed ( Table 5).…”

“…BAILs-1 and -2 exhibited higher acidity than H 2 SO 4 and single SO 3 H-functionalized BAIL-3 (16), , and BAIL-5 (17) due to the double sulfonic acid groups on cations and two or three acidic HSO 4 − anions in their structure ( Table 1). The content of water in BAILs-1 and -2 ranges from 2.0% to 2.5% (Karl-Fischer titration).…”

“…Thus, developing environmentally benign, highly selective, and efficient alternatives is highly desirable. Recently, single SO 3 H-functionalized Brønsted acidic ionic liquids (BAILs) acting as environment friendly and recyclable catalysts have been successfully applied in selective alkylation p-cresol and phenol with TBA (16)(17)(18). These reported methods demonstrated some advantages such as high conversion and selectivity, mild reaction conditions, ionic liquids could be reused after simple treatment, and so on.…”

Catalytic and mechanistic insights into the production of ethyl levulinate from biorenewable feedstocks

“…On the contrary, catalysts having a mesoporous structure, such as polystyrene based Amberlyst-15 and Purolite 500, showed higher EL yield (>80 %) and lesser DEE formation due to greater accessibility of acid sites to FAL as compared to ethanol 101,102 , Table- Table-3 BMIm IL (Hammet Acidity = 2.5) and comparable to other conventional acids (H2SO4) 108 .…”

About the Acidity-Catalytic Activity Relationship in Ionic Liquids: Application to the Selective Isobutene Dimerization

“…ILs have also been designed to be Brønsted acids by covalently tethering an acid group on the cationic part of the ionic liquids [16,17]. Sulfonic or carboxylic acids have for example been grafted on the imidazolium cation leading to functionalized "Task-Specific-Ionic Liquids" [18,19]. …”