A nitrile is an organic cyanide. Both cyanides and nitriles have the general formula RCN with a triple bond between the carbon and nitrogen (R-CN). The compound commonly called cyanide is actually hydrogen cyanide, HCN. When this compound is dissolved in water, an acidic solution of hydrogen cyanide, also known as prussic acid, is produced. Cyanides are the salts of hydrogen cyanide. All of the inorganic cyanides have inorganic groups such as a metal attached to the CN group. The nitriles have an organic group attached to the CN group. This gives rise to compounds such as methyl cyanide. The nitriles were formerly known as the alkyl cyanides.
The industrial preparation of most cyanides starts with the addition of potassium carbonate to carbon and ammonia gas (Beilby's process) to produce potassium cyanide. The potassium cyanide is then reacted with silver nitrate to give silver cyanide as a precipitate. The silver cyanide is then reacted with the chloride of the desired end product. This yields the appropriate cyanide and silver chloride.
Nitriles are formed by heating amides with phosphorous pentoxide or by treating organic halogen compounds with sodium cyanide. Nitriles can be decomposed by acids or alkalis to give the corresponding carboxylic acid or they can be reduced to give primary amines. Nitriles are solvents for a large range of metal complexes and salts. They are also used as intermediates in a number of processes.
All nitriles and cyanides are poisonous, with the cyanides being the more potent form. They act by paralyzing the respiratory center of the brain. Cyanides and nitriles are sweet smelling (the smell is very reminiscent of almonds), colorless liquids that dissolve in water. Water solubility decreases with increasing molecular weight. Nitriles are also soluble in organic solvents.
As well as the -CN structure of cyanides/nitriles a form also exists which can be expressed as -NC. This form is an isocyanide/isonitrile. The properties of the isocyanides/isonitriles are very similar to the properties of the cyanides/nitriles, but there is a slight rearrangement of the distribution of the electrons within the compound and this has a minor effect on some reactions.Hydrolysis of a cyanide gives an amide (or a carboxylic acid if the reaction is carried to completion), and this reaction can be carried out by boiling the cyanide under reflux with acids or alkalis. Hydrolysis of an isocyanide is catalyzed by acid but not by alkali and the result is an amine. The differences are caused by the fact that the R group is attached to the nitrogen (RNC) in isocyanides but to the carbon (RCN) in cyanides. Some chemicals, such as hydrogen cyanide, exist in both forms in equilibrium. The rate of conversion is very rapid and it is not possible to isolate the two forms. This is an example of isomerism.
Cyanides and nitriles are commercially used in the synthesis of artificial fibers and as powerful fumigants.
Cyanides and nitriles have the same functional group, -CN; cyanides are the inorganic form and nitriles are the organic form. All are poisonous with the inorganic form being the more toxic.
This is the complete article, containing 508 words
(approx. 2 pages at 300 words per page).
