title: Kinetics and mechanism of general acid-catalysed thiolytic cleavage of 9-anilinoacridine.
abstract: The rates of the reactions of 2-mercaptoethanol (2-ME) with 9-anilinoacridine (9-ANA) have been studied in the buffer solutions of 2-ME, hydroxylamine, phosphate and morpholine. Both ionised and non-ionised forms of 2-ME and free hydroxylamine show nucleophilic reactivity toward protonated 9-ANA. The rate constants for general acid-catalysed thiolytic cleavage of protonated 9-ANA reveal a Brønsted plot of slope (alpha) of 0.93 which indicates that probably the rate-determining step involves proton transfer in a thermodynamically unfavourable direction. A stepwise mechanism for thiolysis has been suggested. General acid catalysis could be detected for thiolysis of non-protonated 9-ANA only in the buffer solutions of phosphate and morpholine. General acid catalysis seems to be unimportant when the nucleophile is non-ionised 2-ME which is attributed to the probable occurrence of intramolecular general acid catalysis.
authors.affiliation: Department of Chemistry, Bayero University, Kano, Nigeria.
authors.forename: M N
authors.initials: MN
authors.lastname: Khan
authors.forename: A F
authors.initials: AF
authors.lastname: Kuliya-Umar
mesh_terms: D000143:Acids; D000677:Amsacrine / Q000031:analogs & derivatives* / Q000737:chemistry; D000970:Antineoplastic Agents / Q000737:chemistry*; D002384:Catalysis; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D006898:Hydroxylamines; D007700:Kinetics; D008623:Mercaptoethanol / Q000737:chemistry*; D013329:Structure-Activity Relationship; D013438:Sulfhydryl Compounds
chemical_list: D000143:Acids; D000970:Antineoplastic Agents; D006898:Hydroxylamines; D013438:Sulfhydryl Compounds; D000677:Amsacrine; C022202:9-anilinoacridine; D008623:Mercaptoethanol