Chapter 8
Answers
1 a) dimethylamine
Marks
1
b) nucleophilic substitution
5
c)
2
quaternary ammonium salt
surfactant / detergent / fabric softener or
conditioner/ hair conditioner
2 a) Sn or Fe/HCl
2
Sn or Fe/H2SO4
or H2/Ni can be used as the reducing agent.
b)
AQA Chemistry A2 © Nelson Thornes Ltd 2009
Examiner’s tips
1
The curly arrow must be from the lone
pair. Marks 1 and 2 are for the curly
arrows if shown (M1 and M2).
Mark 3 is for the structure of the
intermediate.
Mark 4 is to show the removal of the
H+. You do not need to show the reagent
here.
Final mark is for the name of the
mechanism.
Do not accept dilute or conc. for these 2
acids or you cannot have HNO3
at all.
Do not accept NaBH4/ LiAlH4 or
Na/C2H5OH.
NH3+ is also acceptable.
1
Chapter 8
Answers
c)
Marks
G
Examiner’s tips
2
Do not accept the correct answers
incorrectly labelled.
5
Mark 1, Mark 2 and Mark 4 are for the
curly arrows (M1, M2 and M4).
Mark 3 is for the structure of cation.
Final mark is for the name of the
mechanism.
3
Do not accept HCN here.
Accept 4[H] instead of 2H2.
H
3 a) Nucleophilic substitution
b) Step 1:
CH3CH2CH2Br + KCN →
CH3CH2CH2CN + KBr
(or CN–)
(or Br–)
Step 2
CH3CH2CH2CN + 2H2 →
CH3CH2CH2CH2NH2
c)
i)
You can have 4[H] instead of 2H2.
There is a lone pair (on N);
2
R group increases electron density on
N / has positive inductive effect;
d) CH3CH2N(CH3)2
1
4 a) CH3CH2CH2Br
1
b) CH3CH2CN
1
AQA Chemistry A2 © Nelson Thornes Ltd 2009
Allow Cl instead of Br.
2
Chapter 8
Answers
Marks
Examiner’s tips
c) nucleophilic substitution or from
CH3CH2CH2Br gives less pure produce
because further substitution occurs
The impurity can be any one of
(CH3CH2CH2)2NH
(CH3CH2CH2)3N
(CH3CH2CH2)4N+ Br−
3
Also accept ‘have salts including NH4Br
as impurities’.
5 a) i)
1
Don’t forget to show both charges.
ii)
1
The acid part reacts with the alcohol to
form an ester.
1
Allow COO− But don’t allow O-Na
since this would look covalent.
1
Allow N protonated.
1
There are 2 N atoms which can be
protonated.
b)
AQA Chemistry A2 © Nelson Thornes Ltd 2009
3
Chapter 8
Answers
Marks
Examiner’s tips
c)
1
or
6 a) 2-aminopropanoic acid
1
b) i)
1
Do not accept –CONH− or −COHN−
since you would not be showing how
the link bonded.
ii)
1
Do not accept C3H7 but
is acceptable.
iii)
2
(nucleophilic) addition–elimination
AQA Chemistry A2 © Nelson Thornes Ltd 2009
4
Chapter 8
Answers
c)
Marks
i)
X
1
ii)
Y
1
7 Structure 1 =
2
Examiner’s tips
You cannot have a polypeptide since the
question asked for a dipeptide.
Structure 2 = either
8 a)
1
b) ionic bonding in aminoethanoic acid
AQA Chemistry A2 © Nelson Thornes Ltd 2009
1
Do not accept ‘stronger hydrogen
bonding in aminoethanoic acid.’
This can only be gained if you have
shown that there is ionic bonding in the
solid or stronger attractions than
hydrogen bonding in hydroxyethanoic
acid.
5
Chapter 8
Answers
9 a) 2-aminobutanoic acid
Marks
1
b)
1
10 a)
1
b)
1
c)
hydrogen bonding
In acid solution the amino acid acts as a
base and picks up a proton.
This must be a dipeptid and not a
polymer.
1
11 a) molecules with same structural formula
but with bonds arranged differently in
space
2
b) plane polarised light
rotated equally in opposite directions
2
AQA Chemistry A2 © Nelson Thornes Ltd 2009
Examiner’s tips
Also accept ‘atoms’ arranged differently
in space.
6