Artigo Revisado por pares

Macroscopic and microscopic ionization constants of the thiol and amine groups in 1-methyl-4-mercaptopiperidine

1983; Elsevier BV; Volume: 30; Issue: 7 Linguagem: Inglês

10.1016/0039-9140(83)80127-1

ISSN

1873-3573

Autores

Heribert Barrera,

Tópico(s)

Molecular Sensors and Ion Detection

Resumo

The acid dissociation constants of 1-methyl-4-mercaptopiperidine (pK1 = 9.51, pK2 = 11.33), the 1,1-dimethyl-4-mercaptopiperidinium ion (pKA = 9.59) and 1-methyl-4-(methylthio)piperidine (pKB = 10.18) have been determined potentiometrically in 3M sodium perchlorate (10% methanol) medium. The ultraviolet absorption of the mercaptide ion has been used to determine the relative proton affinity of the sulphur and nitrogen functions in 1-methyl-4-mercaptopiperidine under the same conditions, and its four microscopic constants (pKa = 9.49, pKb = 10.23, pKc = 11.34, pKd = 10.60) have been calculated; pKA has also been determined spectrophotometrically. From the results obtained, it can be concluded that the thiol group is more acidic than the amine group and that the Adams relation, Ka + Kb = K1, holds very well when it is assumed that the spectrophotometric values for Ka, and Kb, can be replaced by KA and KB respectively.

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