title: The kinetics and mechanism of the acid-catalysed detritylation of nucleotides in non-aqueous solution.
abstract: The kinetics and mechanism of the deprotection (detritylation) of 5'-O-(4,4'-dimethoxytrityl)-2'-deoxythymidine nucleoside catalysed by dichloroacetic acid to give a 4,4'-dimethoxytrityl carbocation have been studied in toluene, dichloromethane and acetonitrile. There is little or no effect of solvent polarity on the equilibrium and rate constants. Entropies of activation are highly negative approximately -105 J K(-1) mol(-1) and similarly show little variation with solvent. Addition of small amounts of water to the reaction medium reduces the detritylation rate, presumably through its effect on the solution acidity. All observations are compatible with detritylation occurring through a concerted general acid-catalysed mechanism rather than a stepwise A1 process.
authors.affiliation: Department of Chemical and Biological Sciences, University of Huddersfield, Queensgate, Huddersfield, UK HD1 3DH.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Russell
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Laws
authors.forename: John H
authors.initials: JH
authors.lastname: Atherton
authors.forename: Michael I
authors.initials: MI
authors.lastname: Page
mesh_terms: D000143:Acids / Q000737:chemistry; D000438:Alcohols / Q000737:chemistry; D002384:Catalysis; D003999:Dichloroacetic Acid / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D019277:Entropy; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D015394:Molecular Structure; D009711:Nucleotides / Q000737:chemistry*; D012996:Solutions; D012997:Solvents / Q000737:chemistry; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D000143:Acids; D000438:Alcohols; D009711:Nucleotides; D012996:Solutions; D012997:Solvents; D014867:Water; D003999:Dichloroacetic Acid