Kinetics and mechanism of general acid-catalysed thiolytic cleavage of 9-anilinoacridine

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. Th...

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Bibliographic Details
Published in:Bioorganic & medicinal chemistry 1995-07, Vol.3 (7), p.881-890
Main Authors: Khan, M.Niyaz, Kuliya-Umar, A.F.
Format: Article
Language:English
Subjects:
Acids
Amsacrine - analogs & derivatives
Amsacrine - chemistry
Antineoplastic Agents - chemistry
Catalysis
Hydrogen-Ion Concentration
Hydrolysis
Hydroxylamines
Kinetics
Mercaptoethanol - chemistry
Structure-Activity Relationship
Sulfhydryl Compounds
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Summary: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 (α) 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. Graphic
ISSN:0968-0896
1464-3391
DOI:10.1016/0968-0896(95)00074-Q