| Abstract: | The hydrolysis kinetics of CICN have been reinvestigated from pH 0.0–10.5 and from 18–40°C. In the pH range from 1–5, the hydrolysis rate is invariant and the activation parameters (ΔH? = 84 kJ mol?1 and ΔS? = ?84 J mol?1 K?1) are consistent with water attack. In basic solution the rate is first order each in CICN and OH? concentrations with parameters ΔH? and ΔS? equal to 82 kJ mol?1 and + 54 J mol?1 K?1, respectively. The rate constants with 20 other donors have been measured. Nitrogen nucleophiles are more reactive than oxygen donors, and an alpha-effect is seen. The constants follow a pattern indicative of attack at carbon. Cyanate in its acid form reacts with nucleophiles. Further points on the cyanate rate–pH profile have been obtained. A chromate-catalyzed hydrolysis can contribute between pH 5–10. Some studies were made of the reaction of cyanate with hydrogen peroxide. Free energy correlations are presented. |
