ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Acid-base equilibria of some 2-substituted derivatives of 7-oxo-5,5-dimethyl-4,5,6,7-tetrahydrobenzothiazole

V. Zelenská, V. Madajová, and I. Zelenský

Department of Analytical Chemistry, Faculty of Natural Sciences, Komenský University, 816 50 Bratislava

Abstract: The acid-base equil. of 2-amino-, 2-diethylamino-, 2-hydroxy- and 2-chloro-5,5-dimethyl-7-oxo-4,5,6,7-tetrahydrobenzothiazole in aq. alc. within the acidity range 1 M-H₂SO₄ to 1 M-NaOH was studied spectrophotometrically. The Cl deriv. exists in a single fundamental acid-base form across the whole pH range, but it quite rapidly and irreversibly changes in alk. medium to the 2-hydroxy deriv. In contrast to the 2-chloro and 2-hydroxy derivs., the 2-amino and 2-diethylamino derivs. are protonated in 1 M-H₂SO₄; the 2-amino deriv. is more basic by 0.65 pH units. The 2-diethylamino deriv. is inert in alk. media. The keto-enol tautomeric equil. of the 2-amino deriv. shifts in favor of the undissocd. enol form with increasing EtOH content at const. NaOH concn. The 2-hydroxy deriv. dissocs. readily (pK 7.04).

Full paper in Portable Document Format: 325a658.pdf

Chemical Papers 32 (5) 658–666 (1978)