Microgels with trialkylammonio side chains function as catalysts for the alkaline hydrolysis of substituted phenyl laurate esters
✍ Scribed by D.J. Evans; A. Williams; R.J. Pryce
- Publisher
- Elsevier Science
- Year
- 1995
- Tongue
- English
- Weight
- 561 KB
- Volume
- 99
- Category
- Article
- ISSN
- 1381-1169
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✦ Synopsis
Microgels incorporating 2-(tetradecyldimethylammonio)
ethyl methacrylate bromide have been prepared by emulsion polymerisation with methyl methacrylate, 2-ethoxyethyl methacrylate and ethylene glycol dimethacrylate in the molar ratio 0.15:0.45:0.30:0.10 respectively. The microgel solubilises aryl laurate esters in aqueous solution and catalyses the alkaline hydrolysis of these esters; the variation of rate constant with microgel concentration indicates a complexation phenomenon with the 4-nitrophenyl ester. The reactivity of the microgel sol with the laurate esters is similar to that of the analogous micellar system from cetyltrimethylammonium bromide (CTAB) described by Al-Awadi and Williams (J. Org. Chem., 55 ( 1990) 2001).
The rate constant for the microgel-catalysed reaction of hydroxide ion with the substituted phenyl laurate esters obeys the Bronsted correlation: logk",":, = -0.53pK, + 4.49
The value of the Bronsted & ( -0.53) is similar to that observed for CTAB-catalysis and for uncatalysed alkaline hydrolysis; it indicates that the catalytic site of ester hydrolysis resides in an aqueous-like region of the microgel.