6.2.1 amines Flashcards
naming amines
end in -amine e.g. propylamine
if amine is secondary and has 2 akyl groups attached to nitrogen, then each chain is named and smaller akyl group is preceded by an -N
e.g. N-methylpropylamine
- H3CH2CH2NHCH3
tertiary amine - similar rules, each alkyl side group given an N
e.g. N,N-dimethylpropylamine
- CH3CH2CH2-N-CH3
CH3
properties
primary aliphatic amines act as bases as the lone pair of electrons on nitrogen is readily available for forming a dative covalent bond with H+ and so accepts a proton
stronger bases than ammonia as akyl groups are electron releasing and push electrons towards the nitrogen atom and so make it a stronger base
NH3 + H2O > NH4+ + OH-
strength of aromatic amines
primary aromatic amines e.g. phenylamine, don’t form basic solutions as the lone pair of electrons on nitrogen delocalise with the ring of electrons in benzene ring
N is less able to accept protons
amine + acid
act as base to form ammonium salts
CH3NH2 + HCl > CH3NH3+Cl-
addition of NaOH will convert back to amine
- ionic salts will be solid crystals if water is evaporated due to strong ionic interactions
- ionic salts formed means compounds are soluble in acid
primary amine
can be formed by nucleophilic substitution reaction between haloalkanes and ammonia
reagent: excess ammonia (limits further substitution and maximises amount of primary amine formed) dissolved in ethanol
in 2nd step, second ammonia removes a proton from the intermediate (acts as a base) to form amine
reacting primary amines with haloalkanes
forms secondary amine
same nucleophilic substitution as primary amine
reacting secondary amine with haloalkanes
forms tertiary amine
same mechanism as other amine
reducing nitroarenes to aromatic amines
reagent: Sn and conc HCl
conditions: heating
mechanism: reduction
e.g. nitrobenzene + 6[H] > phenylamine + 2H2O
