amines

• reaction of haloalkanes with ammonia

  -nucleophilic substitution

  -nitrogen lone pair in ammonia acts and nucleophile and replaces the halogen

  -when reacted with XS hot ethanolic ammonia under pressure, primary amine is formed

  eg.

  chloroethane + ammonia --heat, ethanol--> ethylamine + NH4Cl
• reduction of nitriles

  -nitriles contain -Cn which can be reduced to -NH2

  -nitrile vapour and hydrogen gas are passed over a nickel catalyst or LiAlH4 in dry ether can be used to form 1. amine
• production of phenylamine

  step 1 - benzene undergoes nitration with conc HNO3 and conc H2SO4 at 25-60 to form nitrobenzene

  step 2 - nitrobenzene reduced with hot tin and conc HCl under reflux

  step 3 - NaOH added to form phenylamine

  step 4 - phenylamine separated from reaction mixture by steam distillation
• basic properties of amines

  -nitrogen atom in ammonia and amine can accept a proton

  -act as bases in aq solns by donating its lone pair to a H+ to form a dative bond
• strength of ammonia and amines as bases

  -strength depends on ability of lone pair on nitrogen atom to accept a proton and form a dative bond

  -more readily a proton is attracted - stronger the base
• factors affecting basicity of amines: positive inductive effect

  -some groups like alkyl groups donate electron density to N causing lone pair of electron to become more available - increasing bacisity
• factors affecting basicity of amines: delocalisation

  -presence of aromatic rings causes the lone pair of electrons on N to be delocalised into ring

  -lone pair becomes less available to form dative bond with ammonia and hence decreases the amine's basicity
• ethylamine as a base

  positive inductive effect alkyl group donates electron density to N causing lone pair to become more available

  -strongest base out of ammonia and phenylamine
• ammonia as a base

  -no electron donating groups to cause +ve inductive effect

  -no aromatic rings to cause delocalisation of N lone pair

  -weaker than ethylamine not as weak as phenylamine
• phenylamine as a base

  nitrogens lone pair becomes delocalised in benzene ring and therefore less available to form dative covalent bond with H+

  -weakest out of ethylamine and ammonia
• quaternary amine salts

  -chemical analogues to ammonium chloride NH4Cl in which hydrogens have been replaced by 4 alkyl groups

  -useful in manufacture of cleaning products

  -manufacture of conditioners for hair and fabric softeners
• quaternary amine salts as cationic surfactants

  -are chemicals that lower the surface tension between immiscible liquids that allow wetting

  -cationic due to +ve charge on N

  -hydrocarbon groups are hydrophobic and amine group is hydrophilic

  -allows molecules to cluster on surface with heads in water and tails on the surface
• cationic surfactants - conditioner or fabric softener

  -when hair or clothing is wet it can pick up -ve charges that facilitate build up of static electricity

  -conditioner or softener is attracted to wet surfaces due to +ve charge on surfactant

  -forms coating on hair or clothing giving a smooth coating preventing build up of static