Issue 3, 2002

General base catalysis vs. medium effects in the hydrolysis of an RNA model

Abstract

The interpretation of buffer catalysis data is always subject to a degree of uncertainty, because changing the concentration of the catalyst necessarily changes the medium. The history of the imidazole-catalysed reactions of ribonucleotide derivatives is a classic illustration of the potential problems, which are complicated further by significant sensitivity to ionic strength and specific salt effects. Results are reported for the hydrolysis of 4-nitrophenoxymethyl uridine 3′-phosphate, which releases the chromophoric p-nitrophenolate on cleavage of the P–OCH2OAr bond. In the case of catalysis by imidazole, a bell-shaped dependence on the buffer ratio is explained in terms of a solvent effect on the background, hydroxide-catalysed reaction. Results for six other amine bases with pKa = 7 ± 1 show that, in this system, non-linear behaviour is the norm rather than the exception.

Graphical abstract: General base catalysis vs. medium effects in the hydrolysis of an RNA model

Supplementary files

Article information

Article type
Paper
Submitted
15 Oct 2001
Accepted
21 Dec 2001
First published
28 Jan 2002

J. Chem. Soc., Perkin Trans. 2, 2002, 422-427

General base catalysis vs. medium effects in the hydrolysis of an RNA model

A. J. Kirby and R. E. Marriott, J. Chem. Soc., Perkin Trans. 2, 2002, 422 DOI: 10.1039/B109325H

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