Esterolyses of p-nitrophenyl esters catalyzed by dialkylaminopyridines attached to polyorganosiloxane |
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Authors: | Nobukatsu Nemoto Masayuki Aizawa Yukihiko Ueno Koji Ikeda Nobuo Takamiya |
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Affiliation: | (1) Department of Chemistry, School of Science and Engineering, Waseda University, 169 Tokyo, Japan;(2) Department of Imagiscience and Engineering, Faculty of Engineering, Chiba University, 260 Chiba, Japan |
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Abstract: | Summary The present study describes the preparation of polyorganosiloxanes containing dialkylaminopyridines in their side chains (POS-DAAPs) and the use of them as catalysts for esterolyses of p-nitrophenyl esters of CH3(CH2)
n
COOH (n=0–5). The POS-DAAPs (4, 5) were prepared from poly(3-chlorocarbonylpropyl)methylsiloxane] (PCCPMS, 1) and two pyridine derivatives, such as 4-(2-hydroxyethyl)methylamino]pyridine (HEMAP, 2) and 4-4-(2-hydroxyethyl)piperidino]pyridine (HEPP, 3). Pyridyl groups of POS-DAAPs 4 and 5 were partially quaternized with dimethylsulfate (6, 7) in order to carry out esterolysis in homogenious systems. The esterolyses were examined in methanol/tris(hydroxymethyl)-aminomethane-hydrochloric acid buffer solution (vol. ratio 2/1, pH of buffer solution: 7.5) and analyzed following Michaelis-Menten like kinetics. The second-order rate constants (k
2/K
m) of the esterolyses catalyzed by POSs 6 and 7 were 22–38 fold values of those catalyzed by the corresponding monomolecular catalysts 2 and 3. In addition, the effects of POSs were discussed from the kinetic, thermodynamic, and activation parameters. |
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