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

Kinetics of the substitution reactions of chromium(III) complexes. II. Aquation of dibromotetra-aquochromium(III) and bromopenta-aquochromium(III) ions

V. Holba, M. Dillinger, and G. Čunderlíková

Komenský University, Bratislava

Abstract: cf. CA 62, 1118d. Kinetics of the aquation of [CrBr₂(H₂O)₄]⁺ and of [CrBr(H₂O)₅]²⁺ in relation to pH were studied. There are 2 reactions, (A) [CrBr₂(H₂O)₄]⁺ + H₂O →k [CrBr(H₂O)₅]²⁺ + Br^- and (B) [CrBr(H₂O)₅]²⁺ + H₂O →k [Cr(H₂O)₆]³⁺ + Br^-. The liberated Br- were detd. by potentiometric titration with 0.01N AgNO₃ and measured by a spectrophotometric method. In (A) the pH range was 1.0-2.0, temp. 15°, and the kinetic const. was k[min.-1] = 1.60 × 10^-2 + 5.39 × 10^-4/[H+]. In (B) the pH range was 1.80-3.13, temp. 25° and the kinetic const. was k[min.-1] = 1.20 × 10^-2 + 5.61 × 10^-5/[H+]. It is evident from these equations that the conjugated base reacts more rapidly than the original complex ion and that it contributes to the total reaction rate.

Full paper in Portable Document Format: 1811a823.pdf (in Slovak)

Chemical Papers 18 (11) 823–829 (1964)