ANSWER MODEL PSPM DK204 KMKt SET 7

ANSWER SCHEME MODEL PSPM DK024 KMKt- SET 7

1. (a) i. Define functional group

Funtional group is an atom or group of atom in an organic molecule that determine 1M
the chemical properties of a compound 5M

ii. Identify(circle) and name all the functional groups that present in the following

molecule:

halogen

HH H H H Cl O
H C C C O C C C C OH carboxyl

C=C double HH H
bond alkoxy Aromatic ring

(b) For each of the following compounds, draw its isomeric pair that represents a chain,

positional and functional group isomerism;

i. H3C CH2 CH2 CH2 OH

Positional Isomerism HO

H3C CH2 CH2 CH2 OH and H3C CH2 CH CH3

Chain Isomerism and H3C
H3C CH2 CH2 CH2 OH H3C CH CH2 OH

Funtional Group Isomerism H3C CH2 O CH2 CH3 3M

zH3C CH2 CH2 CH2 OH and
ii. O

H3C CH2 CH2 CH

Positional Isomerism
no isomer

Chain Isomerism and H3C O
O H3C CH CH

H3C CH2 CH2 CH

Funtional Group Isomerism

O and O CH3 2M
H3C CH2 CH2 CH H3C CH2 C

(b) Name the type of reaction for the following equations:

+i.
H3C CH2CH2 CH2Br KOH/ethanol H3C CH2 CH CH2 HBr

Elimination CH2 CH3 + HCN OH 1M
ii. O H3C C CH2 CH3 1M
1M
H3C C CN
1M
Nucleophilic addition @ addition CH2 Cl 1M

iii. H3C CH3 + Cl2/uv H3C CH3
H3C C CH2
Free radical substitution
Cl Cl
iv. CH3
Br
+H3C C CH2 Cl2 CH2Cl2

Electrophilic addition @ addition

v.
+ Br2 FeBr3

Eoectrophilic substitution @ substitution
(c) Draw all possible isomer of C7H7Br contain a aromatic ring

Br Br Br 4M
CH3 H3C 21M
Total H2C
CH3 Br

2. (a) Draw the structural formula for 1-chloro-4-ethyl-2-propylcyclopentane 1M
(b) Cl
CH2CH2 CH3 1M
1M
H3C CH2 1M
Which has higher boiling point; hexane or 2-methylpentane? Explain. 1M
Hexane
Hexane is a linear chain alkane, 2-methylpentane is a branched chain alkane 1M
Hexane larger molecular size/surface area than 2-methylpentane 1M
Hexane has stronger van der Waals forces than 2-methylpentane 1M

(c) Reaction of ethane with liquid bromine in the presence of sunlight is as follows : 1M
CH3CH3 + Br2 sunlight CH3CH2Br + HBr

CH2Cl2

(i) Name the type of reaction.

Free radical substitution

(ii) State the observation made.

Reddish brown colour of bromine decolourised

(iii) Write the reaction mechanism for the propagation step and state the type of
cleavage involved.

H Br H

H3C C H H3C C + HBr
H H

H Br Br H
H3C C Br + Br
H3C C
H H

Homolytic cleavage 1M
TOTAL 8M

3. (a) i. Name the following compounds according to IUPAC nomenclature. 1M
5-ethyl-3,6-dimethyl-2-heptene

ii. Draw the structural formulae of 3-ethyl-1-methylcyclopentene 1M
CH3

CH2 CH3

(b) The reaction scheme below is the reactions of 3-methyl-2-pentene
A

conc H2SO4

H2, Pt CH3 HBr
H2O2
B H3C CH C CH2 CH3 E

HCl Br2 , CH2Cl2

C (major) D

(i) Draw the structural formula of A, B, C, D and E

H3C CH CH3 OR CH3 1M
A OH CH CH2 CH3 H3C CH2 C CH2 CH3 1M
1M
CH3 OH 1M

B H3C CH2 CH CH2 CH3
CH3

H3C CH C CH2 CH3
C H Cl

CH3

H3C CH C CH2 CH3
D Br Br

CH3 1M
H3C CH C CH2 CH3
E Br H 1M
(ii) Name the type of reaction for the formation of C. 1M
1M
Electrophilic addition

(iii) State the rule used to determine structure C.
Markovnikov’s rule

(iv) State the rule used to determine the formation of 3-methyl-2-pentene
Saytzeff’s rule

(c) Cyclohexane and cyclohexene are different in the number of hydrogen atoms and
type of bonds. One’s (1) of chemical test to differentiate both compounds is Baeyer’s
test using in cold condition. Write the equations and state the observations involved.

+ KMnO4 OH 1M

cold + MnO2

OH

Observation: purple colour of KMnO4 decolourised and brown precipitate (MnO2) is formed. 1M

+ KMnO4 OH- 1M

no observable change 1M
14M
cold

Observation: purple colour of KMnO4 remains unchanged.

TOTAL

4. (a) Draw the structural formulae of three (3) different classes of alcohols with molecular
formula of C4H10O.
1M+1M
H3C 1M+1M
H3C CH2 CH2 CH2 OH 10 or H3C CH CH2 OH

H o

H3C CH2 C CH3 2

OH

H3C 1M+1M

H3C C CH3 0
OH
3

(b) Explain why alcohol has higher boiling point than alkane with the same molecular
weight.
•Alcohols have higher boiling point than alkanes because alcohols contain hydroxyl 1M
group(-OH)
•Intermolecular forces between alcohols molecules are hydrogen bond and between 1M
molecules alkane are only week Van der Waals forces @
•H-bonding stronger forces than van der Waals forces Bp

(c) Write the equations when 2-methyl-1-propanol reacts with.

(i) Na

(ii) K2Cr2O7/H+, heat

(iii) con. H2SO4, heat

H3C H3C

H3C CH CH2 OH + Na -+ 1M

H3C CH CH2 O Na

H3C H+ H3C O
heat H3C CH C
+H3C CH CH2 OH K2Cr2O7 OH 1M

H3C conc H2SO4 H3C CH2 1M
H3C CH CH2 OH  H3C C 11M
TOTAL

5. (a) (i)Complete the following table.

CARBONYL COMMON NAME IUPAC NAME
STRUCTURE
W methanal
A: HCHO acetone X
Y ethanal
B: CH3COCH3 benzaldehyde Z

C: CH3CHO
O
CH

D:

E: Acetophenone 1-phenylethanone
W = formaldehyde
X = propanone 1M
Y = acetaldehyde 1M
Z = benzenecarbaldehyde 1M
1M
O

C CH3

E= 1M

(ii) State which carbonyl structure(s) of A to E that gives a positive Tollens’ 1M
test. Explain. 1M
A, C, D,
Aldehyde, contains CHO , carbonyl that can be oxidized by oxidizing agent

(b) Based on reaction scheme below.

(i) Suggest reagent x. 1M

x : PCC, CH2Cl2 1M
(ii) Draw the structures of P and Q. 1M

P : CH3CH2COOH 1M
Q: CH3CH2CH(OH)(CN)

(iii) Name the type of reaction for the formation of Q.
Nucleophilic addition
(d) From reaction scheme below;

(i)Draw the structural formulae of R, S and T. 1M
O 1M
C CH3

R
O
C O-Na+

S

HO 1M
H3C C H

T 1M
(ii) Give reagent y 15M
2,4-dinitrophenylhydrazine @ 2,4-DNPH
TOTAL

6. (a) H3C O O
H3C CH C
OH HC OH
A B

O OO
C OH HO C C OH

D 1M
C
1M
Which of the above 1M
i. Dissolves easily in water
A, B, D
ii. Has the highest boiling point. Explain
D
Carboxylic acid with the multiple carboxylic acid group can form more hydrogen bond
(more stronger)

iii. Give the IUPAC name of A 1M
2-methybutanoic acid

(b) The molar mass organic molecules are shown as below:

Molecule Molar Mass (gmole-1)
Propanone 58
Butane 58
1-propanol 60
Methanoic acid 60

Arrange these organic molecules in order increasing boiling point. Explain your 1M
answer.
Butane < Propanone < 1-propanol < Methanoic acid

Butane lowest because ia a non polar molecule. The intermolecular force between 1M
butane is weak van Der Waal force( London force)
Propane polar molecule. The intermolecular force between propane van Der Waal 1M
force (dipole-dipole interaction force)
1-propanol and methanoic acid can form hydrogen bond between molecule but 1M
methanoic acid can form more stable hydrogen bonded dimer between molecule. 1M

(c) Based on the following reaction scheme;

NaOH H3C O Na
C P
R HO CH2 C OH

CH3

+

H3C OH H2SO4

Draw the structure of P,Q and R

H3C O 1M

HO CH2 C C O-Na+ NaOH H3C O Na H3C O 1M
CH3
HO CH2 C C OH -+ C -+ 1M
R CH3
O Na CH2 C O Na
+
CH3
P

H3C OH H2SO4

H3C O O CH3

HO CH2 C C
CH3
Q

TOTAL 12M