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1
Subject: Chains and Rings
Code: 2812
Session: January
Year: 2003
Final Mark Scheme
25/1/2003
MAXIMUM MARK
Mike Smith
Page 1
60
24/02/2003
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3
1.
(a)(i) B
[1]
(ii)
C
[1]
(iii)
B
[1]
(iv)
A
[1]
(b)
equation
C4H9Br + NH3 → C4H9NH2
name:
1-aminobutane/(n-)butylamine/butan-1-amine
solvent
ethanol/alcohol
(c) (i) lone pair (of electrons) donor
(ii)
and
[1]
+ HBr
(or C4H9NH3+Br-)
[1]
[1]
[1]
[1]
oo
o
o
o
xH
O
oo
(iii)
C
If diagram shows a total of 8 electrons
[1]
and has a negative charge.
[1]
only award if the diagram shows 8 electrons
unambiguous identification of organic product:
2-methylpropan-1-ol,
(CH3)2CHCH2OH
H
CH3
H C C
H H
[1]
H
C H
OH
[Total : 12]
Mike Smith
Page 3
24/02/2003
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4
2. (a)(i)
same molecular formula -different structure
[2]
same formula -different structure only scores 1 mark
(ii)
H H Br
H Br H
H C C C Br
H C C C Br
H
H H H
Br
C C C Br
H
H
3
[1]
(iii)
Br
Br
C C C H
C C C H
H
H
2
1
Br H H
H Br H
4
5
[1]
[1]
1,1-dibromopropene
[1]
(b)
(i)
H3C
H3C
H
C C
C C
[1]
Br
cis
Br
Br
Br
[1]
H
trans
(ii)
bond angle = 120o ± 4o
[1]
(iii)
Each C in the C=C is not bonded to two different atoms/groups/
or equivalent.
[1]
Must be 1,3-dibromopropene.
[1]
(iv)
[Total : 11]
Mike Smith
Page 4
24/02/2003
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5
3.
(a)
(i)
H
[1]
(ii)
G
[1]
(iii)
van der Waals/ instantaneous or temporary induced dipoles
[1]
(b)
(i)
contains a single/unpaired/lone electron/ not free electron
[1]
(ii)
Br2 → 2 Br•
[1]
(iii)
Homolysis/ homolytic fission/homolytic cleavage
[1]
(iv)
Br• + C5H12 → •C5H11 + HBr
[1]
•C5H11 + Br2 → C5H11Br
[1]
(c)
+ Br•
I
isomer G,
1
[1]
II
isomer H,
3
[1]
III
isomer I,
4
[1]
[Total : 11]
Mike Smith
Page 5
24/02/2003
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6
4. (a)
(i)
C10H20O
[1]
(ii)
alcohol/ OH/ hydroxy(l)
[1]
secondary
[1]
(b)
or
or
and
1 mark for each alkene
[2]
(c)
O
O
or
or
O C CH3
OOCCH3
or
or
O2CCH3
OCOCH3
O
or full structural formula showing all the atoms
1 mark is available for the ester group showing CH3 bonded via COO to a ring
2 marks for structure as shown
[2]
[Total : 7]
Mike Smith
Page 6
24/02/2003
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7
5. (a) (i)
electrophilic
[1]
addition
[1]
(ii)
intermediate
1 mark
H2C
CH2
H2C CH2
+
Cl
Clδ +
Cl δ−
curly arrow
must be from
the pi-bond
1mark
4 marking points:
(c)
(i)
look for 2 Cl +
backbone of 4 C’s
curly arrow
to show hetrolysis
of the Cl-Cl bond
1 mark
Cl
ClH2C
CH2Cl
curly arrow
1mark
dipoles
or 1 mark
curly arrow from double bond to Cl2,
curly arrow showing movement of electrons in the Cl-Cl bond or the
dipole in the Cl-Cl,
Intermediate carbocation/carbonium ion,
Curly arrow from Cl- to intermediate.
[4]
H Cl H Cl
[1]
C C C C
H H H H
(ii)
H2C +CH2
Cl
“must show end-bonds”
general problems:
non-biodegradable/ not broken down by bacteria/ do not decompose
[1]
when burnt toxic fumes are produced
[1]
[1]
specific problem of PVC:
also produce HCl/ Cl free radicals when burnt
(ii)
removal of toxic products or HCl formed during combustion by gas scrubbers/ by
dissolving in a spray of alkali/ recycling/feedstock recycling/use energy from
combustion for domestic heating/ manufacture biodegradable polymers . [1]
[Total : 10]
Mike Smith
Page 7
24/02/2003
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8
6.
3 marks for equations,
2 marks for correctly explaining (in words) each of the 3 processes.
1 mark for correctly explaining (in words) 2 of the processes.
Cracking.
equation for long chain alkane into shorter chain alkane + alkene.
[1]
[1]
Isomerisation
equation for straight chain alkane converted into a branched chain alkane
equation could be in the form of:
or
into
anyone of
or
or
Reforming
to show straight chain into ring (& must be balanced with appropriate number of H2.) [1]
+ 4H2
+ 3H2
into
either of
+ 2H2
+ H2
(All three processes require) the use of heat and/or a catalyst
Importance of the products:
•
•
•
•
•
(Allow once)
max of 3 marks.
[1]
[3]
more volatile/lower boiling points
used in fuels because they burn better/smoother/more efficiently/more efficient fuel
additive to petrol
reduce knocking/pinking/increase octane number or rating
alkenes can form polymers/PVC (see Q5)/alcohols etc
1 mark for quality of written communication to be awarded for clear presentation and
SPAG.
[1]
[Total :8]
Mike Smith
Page 8
24/02/2003