Issue in Honor of Prof. Waldemar Adam ARKIVOC 2007 (viii) 273-278
Table 3. Esterification of various carboxylic acids with primary alcohols using ionic liquid 1
Entrya Acid Alcohol Yieldb of ester (%)
1 CH3CO2H CH3(CH2)3OH 97
2 CH3CO2H CH3(CH2)7OH 98
3 CH3CO2H CH3(CH2)11OH 99
4 CH3CO2H PhCH2OH 96
5 CH3(CH2)2CO2H CH3(CH2)3OH 99
6 CH3(CH2)7CO2H CH3(CH2)3OH 94
7c
CH2=CH-CO2H CH3(CH2)3OH 91
8 C6H11CO2H CH3(CH2)3OH 56
9 PhCO2H CH3(CH2)3OH 56
10 p-HO-C6H4-CO2H CH3(CH2)3OH 63
a Conditions: Acid (10 mmol), alcohol (20 mmol), ionic liquid 1 (1 g), 90oC, 4 h, under nitrogen. b Based on acid taken. cAcrylic acid (20 mmol) and 1-butanol (24 mmol) were taken. Hydroquinone (15 mg) was added as a polymerization inhibitor.
We have demonstrated application of ionic liquids derived from a simple amine for the Fischer esterification to obtain the esters in high yield without use of the organic solvents and with a convenience of the product separation from the catalyst. Our efforts are directed at screening more such ionic liquids for the Fischer esterification to further understand the structure–activity relationship in this system.
Experimental Section
General Procedures. All the chemicals were of reagent grade and used as received. Melting points were determined with Sanyo Gallenkamp MPD350 apparatus and are uncorrected. The moisture content of the ionic liquids was determined with Mettler DL-18 Karl Fischer titrator. The IR spectra were recorded on Perkin-Elmer Spectrum 1 FTIR. 1H NMR (300 MHz) spectra were recorded on Varian Mercury-300 spectrometer. Analysis of the reaction product was performed on a Schimadzu 15A gas chromatogram fitted with a flame ionization detector. A capillary column, Innovax, 60 M length and 0.32 mm ID was used. Esters were identified by gas chromatographic comparison with their authentic samples. Quantification of the product was done by application of the GC response factors generated using the authentic samples of the esters. The ionic liquids (1-3) were prepared by the literature methods.14
Triethylammonium sulfate (1).14 Colorless solid (yield 95%); mp 85-88oC (Lit.14 mp 91oC); water content 2.6%; IR (KBr, cm-1) 2959, 2923, 2670, 2489, 1470, 1425, 1398, 1227, 1057,
ISSN 1424-6376 Page 276 ©ARKAT USA, Inc.
