The carbon material functionalized with NH₂⁺ and SO₃H groups catalyzed esterification with high activity and selectivity

Abstract

A novel carbon-based solid acid was conveniently prepared by heating a mixture of D-glucose, p-toluenesulfonic acid and diphenylammonium tosylate. Its structure was measured by XRD, FT-IR, XPS, 13 C MAS NMR and EA to illustrate that the carbon material has been functionalized with NH 2 + and SO 3 H groups and has a strong "hydrophobic effect". It can be used to catalyze the esterification reaction of carboxylic acids with equimolar amounts of sterically demanding and acid-sensitive alcohols with high reactivity (yield up to 90%) and selectivity (up to 95%) in heptane at 80°C. It could be easily recovered and reused more than ten times without loss of activity.Generally, the esterification reaction between carboxylic acids and alcohols is catalyzed with Brønsted acids such as H 2 SO 4 , p-toluenesulfonic acid, etc. 1,2 Although these catalysts show good activity for esterification reaction, too strong acidity often leads to low selectivity for some acid-sensitive alcohols, such as secondary alcohols which can be converted to alkenes in the presence of a strong acid. 3 In 2000, Tanabe et al. developed a new type of esterification catalyst diphenylammonium triflate ([Ph 2 NH 2 ] + [OTf ] − ), 4 which has a weaker acidity and can be used to catalyze esterification of carboxylic acids with equimolar amounts of secondary alcohols in high yields. Subsequently, Ishihara's group reported that bulky diarylammonium pentafluorobenzenesulfonates ([Ar 2 NH 2 ] + [O 3 SC 6 F 5 ] − ) were more efficient than [Ph 2 NH 2 ] + [OTf ] − in catalytic activity and selectivity. 3,5-7 They assumed that it is the dimeric cyclic ion pairs composed of two diarylammonium cations ([Ar 2 NH 2 ] + ) and two pentafluorobenzenesulfonate anions ([O 3 SC 6 F 5 ] − )which could form a "hydrophobic wall" to promote the esterification reactions. Also their steric hindrance could effectively suppress the dehydrative elimination of secondary alcohols to produce alkenes (Scheme 1). 6 In order to reuse these catalysts, several groups had tried to immobilize these types of ammonium salts on the polymer, but complex synthetic process and instability of the polymer at high temperatures limited their application. [7][8][9] In 2005, Hara's group found a new carbon-based solid sulfonic acid, which was prepared by incompletely carbonizing glucose at high temperatures (over 300°C) to form a carbonbased material first, and then sulfonating it with a large amount of concentrated sulfuric acid. 10 Successive research optimized this preparation method, 11-16 including using aryl sulfonic acid as the resource of sulfonic acid groups to avoid harsh reaction conditions. [17][18][19] This method is a convenient and efficient way to immobilize the sulfonic acid groups on the carbon-based material, and the recyclable catalyst showed good activity for esterification of simple carboxylic acids (such as acetic acid, oleic acid, etc.) and alcohols (such as methanol, ethanol, etc.). 20-24 Strong hydrophobic polycyclic aromatic carbon sheets formed by incomplete carbonizing of o...

Plasticized poly(3‐hydroxybutyrate) with improved melt processing and balanced properties

“…The signals suggested a TBC plasticizer. Indeed, typical 1 H chemical shift values of TBC are 0.90–0.94 ppm for CH 3 from butyl, 1.33–1.40 and 1.56–1.67 ppm for (CH 2 ) 2  from butyl, 2.77–2.90 ppm for CH 2  from citrate, and 4.07–4.22 ppm for the protons in the CH 2  bonded to oxygen. The additional chemical shifts in the NMR spectrum of the PHB granules were at the same positions: δ = 0.92 ppm (t, 9H), 1.38 ppm (m, 6H), 1.60 ppm (m, 6H), 2.80 ppm (d, 2H), 2.90 ppm (d, 2H), 4.08 ppm (t, 4H), and 4.22 ppm (t, 2H).…”

Bioactivity and structure-activity relationship of cinnamic acid esters and their derivatives as potential antifungal agents for plant protection

“…Compounds ethyl ethyl 2-fluorocinnamate ( A11 ) [ 25 ], ethyl 3-fluorocinnamate ( A12 ) [ 26 ], ethyl 4-fluorocinnamate ( A13 ) [ 27 ], ethyl 2-chlorocinnamate ( A14 ) [ 28 ], ethyl 3-chlorocinnamate ( A15 ) [ 29 ], 2-bromocinnamate ( A17 ) [ 25 ], ethyl 3-Bromocinnamate ( A18 ) [ 30 ], ethyl 2-trifluoromethylcinnamate ( A20 ) [ 25 ], ethyl 3-trifluoromethylcinnamate ( A21 ) [ 26 ], ethyl 4-trifluoromethylcinnamate ( A22 ) [ 27 ], methyl cinnamate ( B1 ) [ 25 ], n -propyl cinnamate ( B2 ) [ 31 ], n -butyl cinnamate ( B3 ) [ 31 ], t -butyl cinnamate ( B4 ) [ 32 ], n -amyl cinnamate ( B5 ) [ 33 ], n -hexyl cinnamate ( B7 ) [ 34 ], n -heptyl cinnamate ( B8 ) [ 35 ], n -octyl cinnamate ( B9 ) [ 36 ], cyclohexyl cinnamate ( B10 ) [ 32 ], benzyl cinnamate ( B11 ) [ 37 ], phenyl cinnamate ( B12 ) [ 37 ], t -butyl 2-methoxycinnamate ( C7 ) [ 38 ], t -butyl 4-methoxycinnamate ( C9 ) [ 38 ], t -butyl 4-fluorocinnamate ( C13 ) [ 39 ], t -butyl 4-bromocinnamate ( C15 ) [ 39 ], t -butyl 4-trifluoromethylcinnamate ( C17 ) [ 39 ] and t -butyl 3,4-methylenedioxy cinnamate ( C19 ) [ 40 ] were confirmed by comparison of NMR data with those in literature.…”

SO3H and NH2+ functional carbon-based solid acid catalyzed transesterification and biodiesel production

“…The catalyst showed high activity and selectivity in the catalytic ester condensation, and was recycled ten times without losing the catalytic activity. 21 In the next work, we found GDTCSA also exhibited the high activity for transesterification of different structural carboxylic methyl esters with alcohols, and it was an effective catalyst for the simultaneous esterification and transesterification of a variety of greases having 5 or 20wt% of FFA contents with methanol or isopropanol. In this report, we would describe in detail its catalytic performance for transesterification and biodiesel production.…”