Nitriles

Suffix:    -nitrile or -onitrile

Prefix:    cyano-

Nitriles contain a carbon - nitrogen triple bond (R-CºN or R-CN). They are indirectly related to amides (by the loss of H₂O from a primary amide), and react chemically similar to carboxylic acids and their derivatives.  It should be noted that H-CºN is not truly a nitrile and is named hydrogen cyanide.

When a nitrile group is the highest priority functional group present in the molecule, it is named as an alkanenitrile (alkenenitrile, alkynenitrile, ...). Since the -CºN must occur at the end of a chain of carbon atoms, the carbon of the nitrile will be carbon 1 in the numbering scheme. Other functional groups are located by this numbering scheme. Since the nitrile group is always at carbon number 1, there is no need to indicate its' location.

Examples naming simple nitriles:

Compound Name	Line Drawing	3D Model
ethanenitrile
propanenitrile
butanenitrile
2-methylpropanenitrile
cyclobutyronitrile *
pentanedinitrile **

* note: the -yl is changed to a -yro.
** note: numbers are not needed as the nitriles must be at the ends of the chain.

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Examples naming more complex nitriles:

Compound Name	Line Drawing
4,4-dimethylpentanenitrile
2,4-pentadienenitrile
4-amino-3-hydroxy-2-methylhexanenitrile
4-chloro-2-cyclohexenenitrile
2-mercapto-4-oxo-6-heptynenitrile

Physical properties Boiling points The small nitriles are liquids at room temperature. nitrile boiling point (°C) CH3CN 82 CH3CH2CN 97 CH3CH2CH2CN 116 - 118
These boiling points are very high for the size of the molecules - similar to what you would expect if they were capable of forming hydrogen bonds. However, they don't form hydrogen bonds - they don't have a hydrogen atom directly attached to an electronegative element. They are just very polar molecules. The nitrogen is very electronegative and the electrons in the triple bond are very easily pulled towards the nitrogen end of the bond. Nitriles therefore have strong permanent dipole-dipole attractions as well as van der Waals dispersion forces between their molecules.
Solubility in water Ethanenitrile is completely soluble in water, and the solubility then falls as chain length increases. nitrile solubility at 20°C CH3CN miscible CH3CH2CN 10 g per 100 cm3 of water CH3CH2CH2CN 3 g per 100 cm3 of water The reason for the solubility is that although nitriles can't hydrogen bond with themselves, they can hydrogen bond with water molecules. One of the slightly positive hydrogen atoms in a water molecule is attracted to the lone pair on the nitrogen atom in a nitrile and a hydrogen bond is formed. There will also, of course, be dispersion forces and dipole-dipole attractions between the nitrile and water molecules. Forming these attractions releases energy. This helps to supply the energy needed to separate water molecule from water molecule and nitrile molecule from nitrile molecule before they can mix together. As chain lengths increase, the hydrocarbon parts of the nitrile molecules start to get in the way. By forcing themselves between water molecules, they break the relatively strong hydrogen bonds between water molecules without replacing them by anything as good. This makes the process energetically less profitable, and so solubility decreases.