Protonation<unk>  is basic. The pKa of hydrogen<unk>  is 9.21. Thus, addition of acid to solutions of<unk>  salts releases hydrogen<unk> . Hydrolysis<unk>  is unstable in water, but the reaction is slow until about 170 °C. It undergoes hydrolysis to give ammonia and formate, which are far less toxic than<unk> : :CN− + 2H2O → HCO2− + NH3<unk>  hydrolase is an enzyme that catalyze this reaction. Alkylation Because of the<unk>  anion's high nucleophilicity, cyano groups are readily introduced into organic molecules by displacement of a halide group (e.g., the chloride on methyl chloride). In general, organic<unk> s are called nitriles. In organic synthesis,<unk>  is a C-1 synthon; i.e., it can be used to lengthen a carbon chain by one, while retaining the ability to be functionalized. :RX +<unk> − → RCN + X− Redox The<unk>  ion is a reductant and is oxidized by strong oxidizing agents such as molecular chlorine (Cl2), hypochlorite (ClO−), and hydrogen peroxide (H2O2). These oxidizers are used to destroy<unk> s in effluents from gold mining. Metal complexation The<unk>  anion reacts with transition metals to form M-CN bonds. This reaction is the basis of<unk> 's toxicity. The high affinities of metals for this anion can be attributed to its negative charge, compactness, and ability to engage in π-bonding. Among the most important<unk>  coordination compounds are the potassium ferrocyanide and the pigment Prussian blue, which are both essentially nontoxic due to the tight binding of the<unk> s to a central iron atom. Prussian blue was first accidentally made around 1706, by heating substances containing iron and carbon and nitrogen, and other<unk> s made subsequently (and named after it). Among its many uses, Prussian blue gives the blue color to blueprints, bluing, and cyanotypes.
Cyanide
Lewisite
Bromide
Hydrogen fluoride
Carbonated water
Carbon monoxide
Isothiocyanate
Metaldehyde