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*Revision Materials* 1 Atomic Structure 2 Atoms, molecules and stoichiometry 3 Chemical Bonding 4 States of matter 5 Chemical energetics 6 Electrochemistry 7 Equilibria 8 Reaction kinetics 9 The Periodic Table, chemical periodicity 10 Group 2 11 Group 17 12 Nitrogen and sulfur 13 Organic 14 Hydrocarbons 15 Halogen compounds 16 Hydroxy compounds 17 Carbonyl compounds 18 Carboxylic acids and derivatives 19 Nitrogen compounds 20 Polymerisation 21 Organic synthesis 22 Analytical techniques 23 Chemical energetics 24 Electrochemistry 25 Equilibria 26 Reaction kinetics 27 Group 2 28 Chemistry of transition elements 29 Organic 30 Hydrocarbons 31 Halogen compounds 32 Hydroxy compounds 33 Carboxylic acids and derivatives 34 Nitrogen compounds 35 Polymerisation 36 Organic synthesis 37 Analytical techniques

19 Nitrogen compounds

19.1 Primary amines 19.2 Nitriles and hydroxynitriles

Nitriles and Hydroxynitriles

Specification Reference Organic Chemistry, Nitrogen compounds 19.2

Quick Notes

  • Nitriles contain a CN functional group
    • Can be made by reacting a halogenoalkane with KCN in ethanol, heated.
  • Hydroxynitriles contain an OH and CN group bonded to the same carbon
    • Can be made by reacting aldehydes or ketones with HCN, using KCN as catalyst and heating.
  • Nitriles hydrolyse with dilute acid or alkali (followed by acidification) to form a carboxylic acid.

Full Notes

Nitriles and hydroxynitriles and their reactions have been outlined in more detail here.
This page is just what you need to know for CIE A-level Chemistry :)

Formation of Nitriles

Nitriles can be made by reacting a halogenoalkane with KCN in ethanol.

CIE A-Level Chemistry reaction scheme showing halogenoalkane reacting with KCN in ethanol under reflux to form a nitrile.

Reaction:
Halogenoalkane + KCN → Nitrile + KX

Reagents: Potassium cyanide (KCN) in ethanol
Conditions: Heat under reflux

The cyanide ion (CN−) acts as a nucleophile, replacing the halogen atom in a nucleophilic substitution. This increases the carbon chain by one carbon atom.

Example CH3CH2Br + KCN → CH3CH2CN + KBr

Photo of Matt
Matt’s exam tip

The forming of nitriles from halogenoalkanes is a really useful and important reaction for organic exam questions! This is because it enables the length of carbon chain to be increased. If the carbon chain in a molecule has got larger in a reaction - this should be the first reaction you think of and check.

Formation of Hydroxynitriles

Hydroxynitriles can be made by reacting aldehydes or ketones with HCN.

CIE A-Level Chemistry reaction scheme showing aldehyde or ketone reacting with HCN (generated from KCN and acid) to form a hydroxynitrile.

Reaction:
Aldehyde or ketone + HCN → Hydroxynitrile

Reagents: HCN (generated in situ from KCN and dilute acid)
Conditions: Heat gently

This reaction adds CN− and H+ across the C=O group to give an extra C–C bond. This is a nucleophilic addition reaction.

Notes: HCN is generated in situ by reacting KCN with H2SO4 because pure HCN is too toxic and volatile to handle safely. The KCN supplies CN− ions, while H2SO4 provides H+ ions. This combination produces the same product — a hydroxynitrile — without needing to use HCN directly.

Example CH3CHO + HCN → CH3CH(OH)CN (2-hydroxypropanenitrile)

CH3COCH3 + HCN → CH3C(OH)(CN)CH3

Hydrolysis of Nitriles to Carboxylic Acids

Nitriles can by hydrolysed to form carboxylic acids.

CIE A-Level Chemistry reaction scheme showing nitrile hydrolysed under dilute acid or alkali to form a carboxylic acid.

Reaction:
R–CN + 2H2O + HCl → R–COOH + NH4Cl
(or with alkali: R–CN + NaOH + H2O → R–COO− + NH3, then acidify to form R–COOH)

Reagents:
Dilute HCl or NaOH, followed by acidification

Conditions:
Heat under reflux

Summary