Hydrogen+Cyanide

Hydrogen cyanide is weakly [|acidic] with a [|pKa] of 9.2. It partly [|ionizes] in water solution to give the [|cyanide] anion, CN–. A [|solution] of hydrogen [|cyanide] in [|water] is called hydrocyanic acid. The [|salts] of hydrogen cyanide are known as cyanides. HCN has a faint, bitter, [|almond]-like [|odor] that only some people are able to [|detect] owing to a [|genetic] [|trait].The [|volatile] compound has been used as inhalation [|rodenticide] and human poison. Cyanide ions interfere with iron-containing respiratory enzymes. HCN is produced on an industrial scale and is a highly valuable precursor to many chemical compounds ranging from [|polymers] to pharmaceuticals.
 * Hydrogen cyanide** (with the historical common name of **Prussic acid**) is a [|chemical compound] with [|chemical formula] HCN. It is a [|colorless], extremely [|poisonous] liquid that [|boils] slightly above [|room temperature] at 26 °C (79 °F). Hydrogen cyanide is a linear molecule, with a [|triple bond] between carbon and nitrogen. A minor [|tautomer] of HCN is HNC, [|hydrogen isocyanide].

Hydrogen cyanide forms in at least limited amounts from many combinations of hydrogen, carbon, and ammonia. Hydrogen cyanide is currently produced in great quantities by several processes, as well as being a recovered waste product from the manufacture of [|acrylonitrile] .In the year 2000, 732,552 tons were produced in the US. The most important process is the [|Andrussow oxidation] invented by [|Leonid Andrussow] at [|IG Farben] in which [|methane] and [|ammonia] react in the presence of [|oxygen] at about 1200 °C over a [|platinum] catalyst: 2 CH4 + 2 NH3 + 3 O2 → 2 HCN + 6 H2O The energy needed for the reaction is provided by the partial oxidation of methane and ammonia. Of lesser importance is the [|Degussa] process ( [|BMA process] ) in which no oxygen is added and the energy must be transferred indirectly through the reactor wall: CH4 + NH3 → HCN + 3H2 This reaction is akin to [|steam reforming], the reaction of [|methane] and water to give [|carbon monoxide] and [|hydrogen]. In the Shawinigan Process, [|hydrocarbons], e.g. [|propane] , are reacted with ammonia: C3H8 + 3 NH3 → 3 HCN + 7 H2 When heated strongly, [|formamide] decomposes to hydrogen cyanide and water vapor: CH(O)NH2 → HCN + H2O In the laboratory, small amounts of HCN are produced by the addition of acids to cyanide salts of [|alkali metals] : H+ + NaCN → HCN + Na+ This reaction is sometimes the basis of accidental poisonings because the acid converts a nonvolatile cyanide salt into the gaseous HCN.