CHEMISTRY 3.5
WORKSHEET SIX
ANSWERS
ORGANIC CHEMISTRY
Amines
1.
(a)
2.
If the nitrogen atom is bonded to three carbons it is a tertiary amine. If the
nitrogen is bonded to two carbons it is a secondary amine and if the nitrogen
is bonded to only one carbon it is a primary amine.
3.
(a)
(c)
(e)
4.
CH3CH2Cl
5.
For primary and secondary amines, the presence of the N-H bond enables the
amine molecules to hydrogen bond to water molecules. This allows them to
dissolve in water. With higher Mr this solubility decreases.
Although both primary amines and alcohols can form hydrogen bonds to
each other, the hydrogen bonding in alcohols is stronger than in amines as O
is more electronegative than N and so the boiling point is higher..
Amines are stronger bases than ammonia.
6.
7.
Ethylamine and aminoethane (b) Pentylamine and 1-aminopentane
aminomethane / methylamine (1e)
(b) dimethylamine (2e)
trimethylamine (3e)
(d) ethylmethylamine (2e)
diethylmethylamine (3e)
(f)
aminoethane / ethylamine (1e)
Alcohol/NH3
CH3CH2NH2
8.
(a)
(b)
(c)
CH3CH2NH2 + H2O  CH3CH2NH3+(aq) + OH-(aq)
(CH3CH2)2NH + H2O  (CH3CH2)2NH2+(aq) + OH-(aq)
(CH3CH2)3N + H2O  (CH3CH2)3NH+(aq) + OH-(aq)
9.
(a)
(b)
CH3CH2NH3+ + H2O  CH3CH2NH2 + H3O+
The pH of the solution in (a) will be acidic as the ethylammonium ion
acts as a weak acid donating a proton to the water molecules.
10.
(a)
(b)
(c)
(d)
CH3CH2NH2 + HCl(aq)
2(CH3CH2)2NH + H2SO4 (aq)
(CH3CH2)3N +
HNO3(aq)
2CH3NH2 +
H2SO4(aq)
11.
(a)
(b)
(c)
(d)
ethylammonium chloride
diethylammonium sulfate
triethylammonium nitrate
methylammonium sulfate
→
→
→
→
CH3CH2NH3+(aq) + Cl-(aq)
2(CH3CH2)2NH2+(aq) + SO42-(aq)
(CH3CH2)3NH+(aq) + NO3-(aq)
2CH3NH3+(aq) + SO42-(aq)