SPM CHEMISTRY : Chapter 2 hydrocarbon

Alkanes
1. General Formula : CnH2n+2 (number of atoms, n = 1,2,3......)
2. They are saturated hydrocarbons;
each carbon atom is bonded to four other atoms by
single covalent bonds.
3. The members of the family, ending with name ―ane‖.
Number of
carbon
atoms
(n)
Name
Molecular formula
CnH2n+2
Molar
mass
(g mol-1
)
Physical
state at
room
temperatu
re
1 Methane C1H2x1+2 = CH4 16 Gas
2 Ethane C2H2x2+2 = C2H6 30 Gas
3 Propane C3H2x3+2 = C3H8 44 Gas
4 Butane C4H2x4+2 = C4H10 58 Gas
5 Pentane C5H2x5+2 = C5H12 72 Liquid
6 Hexane C6H2x6+2 = C6H14 86 Liquid
7 Heptane C7H2x7+2 = C7H16 100 Liquid
8 Octane C8H2x8+2 = C8H18 114 Liquid
9 Nonane C9H2x9+2 = C9H20 128 Liquid
10 Decane C10H2x10+2 = C10H22 142 Liquid
Consecutive members different in molar mass is 14 g mol-1
Bright Minds 016-6412016 Thuran
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4. Structural formulae of alkanes
Name No. of
isomers
Structural formulae and Name
Methane
CH4
0
Ethane,
C2H6
0
Propane,
C3H8
0
Butane,
C4H10
2 H H H H
│ │ │ │
H ─ C ─ C ─ C ─ C ─ H
│ │ │ │
H H H H
n-butane
H H H
│ │ │
H ─ C ─ C ─ C ─ H
│ │ │
H H H
H
│
H ─ C ─ H
│
H
H H
│ │
H ─ C ─ C ─ H
│ │
H H
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Pentane,
C5H12
3
2 - methyl propane
H H H
│ │ │
H ─ C ─── C ─── C ─ H
│ │ │
H H─C─H H
│
H
H H H H H
│ │ │ │ │
H ─ C ─ C ─ C ─ C ─ C ─ H
│ │ │ │ │
H H H H H
n-pentane
H H H H
│ │ │ │
H ─ C ─── C ─── C ─ C ─ H
│ │ │ │
H H─C─H H H
│
H
2-methyl butane
1 2 3 4
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Hexane,
C6H14
5
H
│
H H ─ C ─ H H
│ │ │
H ─ C ─── C ─── C ─ H
│ │ │
H H─C─H H
│
H
2,2-dimetyl propane
H H H H H H
│ │ │ │ │ │
H ─ C ─ C ─ C ─ C ─ C ─ C ─ H
│ │ │ │ │ │
H H H H H H
n-hexane
H H H H H
│ │ │ │ │
H ─ C ─── C ─── C ─ C ─ C ─ H
│ │ │ │ │
H H─C─H H H H
│
H
2 - methyl pentane
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H
│
H H ─ C ─ H H H
│ │ │ │
H ─ C ─── C ─── C ─ C ─ H
│ │ │ │
H H─C─H H H
│
H
2,2 - dimethyl butane
2,3 - dimethyl butane
H H H H H
│ │ │ │ │
H ─ C ─ C ─── C ─── C ─ C ─ H
│ │ │ │ │
H H H─C─H H H
│
H
3 - methyl pentane
H
│
H H H ─C─H H
│ │ │ │
H ─ C ─── C ─── C ─── C ─ H
│ │ │ │
H H─C─H H H
│
H
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Physical Properties
Physical properties of alkanes
i. cannot conduct electrity
ii. less dense than water
iii. dissolve in organic solvents, insoluble in water
iv. low melting and boiling points
Conclusion:
- molecule held together by weak intermolecular forces
- properties of covalent compound
- gradually steady increase as the number of carbon in alkane
increases
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6. Steps to name branched alkanes;
i. determined and named the long chains
ii. determined and named the branch chain
CH3 : methyl
C2H5 OR CH2CH3 : ethyl
C3H7 OR CH2CH2CH3 : prophyl
iii. give number to the carbon atoms in long chain, which started
from the nearest branched
iv. The number for carbon atom which branched emerged from,
must put before/infront the alkyl
v. Named the branched first, followed by the named of long chains
The word ― di, tri‖ is used if the branched chains is more than one
Chemical Properties
Pg 38
Reactivity of alkanes
1. Not reactive/unreactive because saturated hydrocarbon
2. Did not decolourized purple solution of acidified potassium
manganate(VII)
3. Did not decolourized reddish brown solution of bromin water
4. Neutral.
Combustion of alkanes
1. In the presence of sufficient oxygen, alkanes burns to form
carbon dioxide and water. – complete combustion
Chemical equation:
i. CH4 + O2  CO2 + H2O
CH4 + 2O2  CO2 + 2H2O
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ii. C2H6 + 7/2 O2  2CO2 + 3H2O
iii. C4H10 + 13/2 O2  4CO2 + 5H2O
iv. C6H14 + 19/2 O2  6CO2 + 7H2O
Answers
i. CH4 + 2O2  CO2 + 2H2O
ii. C2H6 + 7 O2  2CO2 + 3H2O
2
2 x C2H6 + 2 x 7 O2  2x 2CO2 + 2x 3H2O
2
2C2H6 + 7 O2  4CO2 + 6H2O
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iii. C4H10 + 13/2 O2  4CO2 + 5H2O
iv. C6H14 + 19/2 O2  6CO2 + 7H2O
2. If there is insufficient oxygen, carbon monoxide or carbon
may be formed – incomplete combustion
i. CH4 + 3/2 O2  CO + 2H2O
2CH4 + 3 O2  2CO + 4H2O
ii. CH4 + O2  C + 2H2O
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Halogenation
1. The reaction is between alkane dan chlorine.
2. Takes place under sunlight/ultra violet light.
3. Carbon-hydrogen bonds broken and new carbon-halogen bonds
are formed. One or more hydrogen atoms in alkanes molecule may be
subtituted by halogen.
4. Halogenation is substitution reaction.
Chlorination of methane
First stage;
Second stage;
H H
│ |
H ─ C ─ H +Cl-Cl → H — C — Cl + HCl
│ |
H H monochloromethane
H Cl
│ |
H ─ C ─ Cl + Cl2 → H — C — Cl + HCl
│ |
H H dichloromethane
Third stage ;
Fourth stage;
Cl Cl
│ |
H ─ C ─ Cl + Cl2 → H — C — Cl + HCl
│ |
H Cl trichloromethane
Cl Cl
│ |
H ─ C ─ Cl + Cl2 → Cl — C — Cl + HCl
│ |
Cl Cl tetrachloromethane
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Alkenes
1. General formulae : CnH2n
[ no alkene corresponding to n = 1 as CH2 is not exist]
2. Alkenes is unsaturated hydrocarbon because the presence of the
double bond.
3. Name of each members end with “ene”.
No. of
carbon atom
Name
Molecular
formulae
Molar mass /
g mol-1
Physical
state at room
condition
1 None
2 Ethene C2H4 28 Gas
3 Propene C3H6 42 Gas
4 Butene C4H8 56 Gas
ethenes
Alkenes containing at least one carbon-carbon
double bond
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5 Pentene C5H10 70 Liquid
6 Liquid
7 Liquid
8 Liquid
9 Liquid
10 Liquid
WHEN THE NUMBER OF CARBON IN HYDROCARBON
INCREASES/GREATER/HIGHER, THE SIZE OF HC
MOLECULE IS BIGGER.
THUS, THE INTERMOLECULAR FORCES/Van der Waals
FORCES IS STRONGER.
THUS, MORE ENERGY IS NEEDED TO OVERCOME THE
FORCES.
4. Structure formula for few members of alkenes
Name Number
of isomer
Structure formula and name
Ethene
C2H4
0
H H
│ │
C ═ C
│ │
H H
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Propene
C3H6
0
H H
│ │
C ═ C ─ C ─ H
│ │ │
H H H
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Butene,
C4H8
3
H H
│ │
H ─ C ─ C ═ C ─ C ─ H
│ │ │ │
H H H H
H H
│ │
C ═══ C ─── C ─ H
│ │ │
H H─C─H H
│
H
but -2- ene
2-methyl propene
H H H
│ │ │
C ═ C ─ C ─ C ─ H
│ │ │ │
H H H H
but -1- ene
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Pentene,
C5H10
5
H H H
│ │ │
C ═══ C ─── C ─ C ─ H
│ │ │ │
H H─C─H H H
│
H
2-methylbut -1- ene
H H H
│ │ │
H ─ C ─ C ─ C ═ C ─ C ─ H
│ │ │ │ │
H H H H H
H H H H
│ │ │ │
C ═ C ─ C ─ C ─ C ─ H
│ │ │ │ │
H H H H H
pent -1- ene
pent -2- ene
H H H H
│ │ │ │
C ═ C ─── C ─── C ─ H
│ │ │
H H─C─H H
│
H
3-methyl but -1- ene
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Hexene,
C6H12
12
H H H
│ │ │
H─ C ─── C ═══ C ─C ─ H
│ │ │
H H─C─H H
│
H
2-methyl but -2- ene
H H H H H
│ │ │ │ │
C ═ C ─ C ─ C ─ C ─ C ─ H
│ │ │ │ │ │
H H H H H H
H H H H
│ │ │ │
H ─ C ─ C ═ C ─ C ─ C ─ C ─ H
│ │ │ │ │ │
H H H H H H
H H H H
│ │ │ │
H ─ C ─ C ─ C ═ C ─ C ─ C ─ H
│ │ │ │ │ │
H H H H H H
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H H H H
│ │ │ │
C ═══ C ─── C ─ C ─ C ─ H
│ │ │ │ │
H H─C─H H H H
│
H
H H H H
│ │ │ │
C ═ C ─── C ─── C ─ C ─ H
│ │ │ │ │
H H H─C─H H H
│
H
H H H H
│ │ │ │
C ═ C ─ C ─── C ─── C ─ H
│ │ │ │ │
H H H H─C─H H
│
H
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H H H H
│ │ │ │
H ─ C ─── C ═══ C ─ C ─ C ─ H
│ │ │ │
H H─C─H H H
│
H
H H H
│ │ │
H ─ C ─ C ═══ C ─── C ─ C ─ H
│ │ │ │ │
H H H─C─H H H
│
H
H H H
│ │ │
H─C ─ C ═ C ─── C ─── C ─ H
│ │ │ │ │
H H H H─C─H H
│
H
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H
│
H H─C─H H
│ │ │
C ═══ C ─── C ─── C ─ H
│ │ │ │
H H─C─H H H
│
H
H
│
H H─C─H H
│ │ │
H─ C ─── C ═══ C ─── C ─ H
│ │ │
H H─C─H H
│
H
H
│
H H─C─H H
│ │ │
C ═══ C ─── C ─── C ─ H
│ │ │ │
H H H─C─H H
│
H
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Can you named the molecules?
Steps to name branched alkenes;
i. determined and named the long chains that has double
covalent bond
ii. numbered the carbon atom from the nearest end to double
covalent bond
iii. determined and named the branch chain
CH3 : methyl
C2H5 or CH2CH3 : ethyl
C3H7 or CH2CH2CH3 : prophyl
iii. give number to branched chain
iv. The number for carbon atom which branched emerged
from, must put before/infront the alkyl
v. The word “ di, tri” is used if the branched chains is more
than one
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Physical Properties
Physical properties of alkenes (similar to alkanes)
i. cannot conduct electrity
ii. less dense than water
iii. obeys “ like dissolve like”;
 dissolve in organic solvents
 insoluble in water
iv. low melting and boiling points, gradually steady increase
as the number of carbon in alkene increases
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Chemical Properties
Reactivity of alkenes
1. Alkenes is more reactive because the presence of double
covalent bond, (unsaturated hydrocarbon)
2. Alkenes decolourized purple solution of acidified potassium
manganate(VII)
3. Alkenes decolourized reddish brown solution of bromin water
4. Neutral.
Combustion of alkenes
.
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Addition Reaction (5.2)
The carbon-carbon double bond is converted into
two single bonds
H H H H
   
C = C + X  Y  X  C  C  Y
   
H H H H
Alkenes Molecule Alkanes
(Unsaturated) (Saturated)
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1. Addition of hydrogen
Mixture of alkenes gas/vapour and hydrogen gas, is passed
through platinum or nickel at 180 o
C. The process is known as
catalytic Hydrogenation.
Catalyst: platinum or nickel
H H H H
  Ni/Pt  
C = C + H2  H C  C H
  180o
C  
H H H H
Ethene Hydrogen Ethane
Chemical equation: C2H4 + H2  C2H6
Example use of this process:
Manufacture of margarine is through hydrogenation
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2. Addition of halogens
The process is known as halogenation
H H H H
   
C = C + Br  Br  Br  C  C  Br
   
H H H H
Ethenes Bromine 1,2-dibromoethanes
(unsaturated) (saturated)
Chemical equation: C2H4 + Br2  C2H4Br2
[HW-notes book]
Q1: Write a chemical equation reaction between but-1-ene with
bromine water. Show the structural formula as well.
[HW-exercises book]
Q2: Halogenation process is best used to differentiate between
alkanes and alkenes. Explain how it can be done?
[notes: refer to SAB]
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3. Addition of hydrogen halides
i. Alkenes reacts with hydrogen halide in room condition.
Hydrogen halide molecules is added to double bond in alkenes,
to produce halogenoalkane.
ii. When hydrogen chloride gas is passed through into ethenes,
monochloroethanes is produced.
H H H H
   
C = C + H─Cl  H C  C Cl
   
H H H H
Ethenes Hydrogen chloride Monochloroethanes
Chemical equation: C2H4 + HCl → C2H5Cl
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4. Addition of acidified potassium manganate(VII)
1. When alkenes is mixed with acidified potassium manganate(VII),
its purple colour is decolourised.
2. This is because addition process occurred, a group of
hydroxyl (--OH) is added to the molecules of alkenes to form a
molecule of –diol (type of alcohol) which is saturated and
colourless.
   
C = C + H2O   C  C 
   
OH OH
Alkenes alkanes-diol compound
[O]
[from acidified KMnO4]
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Example;
H H H H
   
C = C + H2O + [O]  H  C  C H
   
H H OH OH
Ethene Ethane-1,2-diol
Q: Use propene as example.
H H H H H
    │
H— C —C = C + H2O + [O]  H  C−C  C H
│   │  
H H H H OH OH
Propene, C3H6 Propane-1,2-diol
C3H6 + H2O + [O]  C3H8O2
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5. Steam
(Hydration process)
1. Alkenes react with steam to produce equivalent alcohol
at the temperature of 300 o
C and in the pressure of 60
atmosphere.
2. Reactions catalyst by concentrated phosphoric acid, H3PO4.
3. This method is one of the industrial preparation to produce
alcohol.
H H H H
   
C = C + H─OH  H C  C  H
   
H H H OH
Ethene Steam Ethanol
C2H4 + H2O → C2H5OH @ C2H6O
Q: Use but-1-ene
C4H8 + H2O  C4H9OH / C4H10O
300 o
C, 60 atm
H3PO4
300 o
C, 60 atm
H3PO4
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Polymerization
5.3
Polymer :Large molecules made up from many identical
repeating sub-units called monomers, which joined
together by covalent bond.
Polymerization is a process of repeated linking
when a monomers are joined into chains
Reaction to form a polymer from alkene monomers is called an
addition polymerisation
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Homologous Series
Characteristic of Homologous Series
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1
Comparing properties of Alkanes and Alkenes
Similarities:
Properties Alkanes & Alkenes
Solubility in water No
Solubility in organic
solvent
Yes
Conductivity No
Boiling and melting
point
Low
Molecular formula
Each member of homologous differs from
the next/successive member by a unit
−CH2−
Molecular mass
Each member of homologous differs from
the next/successive member of 14 unit
Differences:
Properties Alkanes Alkenes
Reaction with oxygen,
O2 gas
It burned with less
sooty yellow flame
It burned with a
more sooty yellow
flame
Reaction with bromine,
Br2 water
The reddish-brown
colour of bromine
water remains
unchanged
The reddish-
brown colour of
bromine water
decolourised
Reaction with acidified
potassium
manganate(VII),
KMnO4 solution
The purple colour of
acidified potassium
manganate(VII)
solutions remained
unchanged
The purple colour
of acidified
potassium
manganate(VII)
solutions was
decolourised
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2
ESSAY;
HOW TO DIFFERENTIATE THE ALKANE and
ALKENE IN THE BOTTLES?
Solutions: i. Procedure
ii. Observations
iii. Inference
[8marks]
Sample answer
Aim: To investigate the liquid in bottle A and B
Test tube A Test tube B
Dropper
Test tube
BA
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3
Procedure;
1. The apparatus shown above is prepared.
2. 2-5 cm3
bromine water is measured with measuring
cylinder 5ml and poured into a test tube.
3. A few drops of liquid from bottle A is put/added with
dropper into the test tube, and shake.
4. Obsevation is recorded.
5. The experiments is repeated by replace the liquid from
bottle A with bottle B.
Observation:
Test Tube Observation Inference
Liquid
in bottle A
The reddish-brown
colour of bromine water
remains unchanged
Contains alkane
Liquid
in bottle B
The reddish-brown
colour of bromine water
decolourised
Contains alkene
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1
ALCOHOL
The Alcohol Family
1. One of member of homologous series which contain carbon,
hydrogen and oxygen.
2. General formula for alcohol is CnH2n+1OH. [n=1,2,3..]
3. Alcohol contains the hydroxyl group, -OH as their functional
group. [notes: not hydroxide ion, OH-
, alcohol not is alkaly ]
4. Alcohol is neutral compound.
5. Alcohol are named by replacing -e for alkane with –ol.
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2
6. Structural formula and molecule for few alcohol.
n Name Mr
Molekul
Formula
Structural formula
1 Methanol
12+3+
16+1
= 32
CH3OH
@
CH4O
H
|
H— C — OH
|
H
2
Ethanol
very
important
12x2 +
5 +16
+ 1 =
46
C2H5OH
@
C2H6O
H H
| |
H— C — C — OH
| |
H H
3
Propan-1-
ol
60 C3H7OH
H H H
| | |
H — C— C — C — OH
| | |
H H H
4
Butan-1-
ol
74 C4H9OH
5
Pentan-1-
ol
88 C5H11OH
6
Hexan-1-
ol
102 C6H13OH
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3
Q: Give names for this alcohol.
OH

CH3  CH2  CH  CH2  CH2  CH3
Formula: C6H13OH
Name : HEXAN-3-OL
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4
Naming Alcohol
1. Find the longest continous carbon chain containing –OH.
2. Number the carbon beginning at the end nearer to the – OH,
write the number in front of the ending –ol.
3. Locate the alkyl group (branch chain), give number to the
carbon and named the alkyl group. Put the number in front of
the group.
 CH3 : methyl
 C2H5 atau CH2CH3 : ethyl
 C3H7 atau CH2CH2CH3 : propyl
4. Complete the name for the alcohol
(ii)
OH

CH3  CH2  C  CH2  CH2  CH3
|
CH3
Formula: C7H15OH
Name : 3-methyl hexan-3-ol
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5
(iii)
OH

CH3  CH2  CH  CH  CH2  CH3
|
CH3
Formula : C7H15OH
Name : 4-methyl hexan-3-ol
(iii)
OH

CH3  CH  CH  CH  CH2  CH2
| | |
CH3 CH3 CH3
Formula : C9H19OH
Name : 2, 4 – dimethyl heptan-3-ol
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6
(iv)
C2H5 OH
 
CH3  CH2  CH  CH2  CH  CH2 ─ CH3
Formula : C9H19OH
Name : 5-ethyl heptan-3-ol
Physical Properties
1. Liquid at room temperature. (pg. 62) [ no gas]
2. Simple alcohol are very soluble in water, infinite solubility.
Methanol, ethanol dan propan-1-ol is miscible in all proportions
(terlarut campur dengan air dalam semua kadaran).
The rest of the alcohol less soluble or insoluble.
Isomerism
Similar to alkenes, isomerism in alcohol results from the
branching of the carbon chain and the different location of the
hydroxyl group.
You only have to know the isomerism in propanol dan butanol.
Q : Draw 2 isomers for propanol and 4 isomers for butanol,
and dan named the isomers.
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7
Propanol
Butanol
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8
Propanol
H H H
│ │ │
H ─ C ─ C ─ C ─ OH
│ │ │
H H H
H H H
│ │ │
H ─ C ─ C ─ C ─ H
│ │ │
H OH H
Molecular formula: C3H7OH
Name: Propan-1-ol
Name: Propan-2-ol
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9
Butanol
Name: Butan-1-ol
Name: Butan-2-ol
H H H H
│ │ │ │
H ─ C ─ C ─ C ─ C ─ OH
│ │ │ │
H H H H
H H H H
│ │ │ │
H ─ C ─ C ─ C ─ C ─ H
│ │ │ │
H H OH H
H H H
│ │ │
H ─ C ─── C ─── C ─ OH
│ │ │
H H─C─H H
│
H
Name: 2-methylpropan-1-ol
H OH H
│ │ │
H ─ C ─── C ─── C ─ H
│ │ │
H H─C─H H
│
H
Name: 2-methylpropan-2-ol
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10
ETHANOL
1. Preparation of ethanol.
i. Laboratory preparation (fermentation)
ii. Industrial production (hydration process)
Making Ethanol Fermentation
1. Two stages;
i. Fermentation
ii. Purification
- through fractional distillation at 78 o
C
( boiling point of ETHANOL)
Fermentation of Glucose
1. Yeast is added to sugar or starch.
2. Anaerobic process ( takes place in the absence of oxygen).
3. Yeast releases enzymes. These enzymes break down the
sugars/starch into glucose, C6H12O6.
4. Zymase slowly decomposes the glucose to form ethanol and
carbon dioxide.
Zymase @ C2H5OH @ C2H6O
C6H12O6 (aq)  2CH3CH2OH (l) + 2CO2 (g)
30 o
C
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When the concentration of ethanol reach 15%, the yeast dies.
Q: How to produce pure alcohol?
A: Purified the ethanol through fractional distillation.
Purification of Ethanol
1. Ethanol produced from the fermentation process is impure,
because its mix with the glucose solution.
Q : Draw labeled diagram to carry out the purification of ethanol
through fractional distillation process.
Delivery tube
Lime water
Beaker
Glucose + yeast
Conical flask
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Q: Why the solution/filtrate in rounded conical must heated at
78o
C.
A: The boiling point of ethanol is 78 o
C.
Q: Ethanol produced may still contains of some water.
What should be done to be sure that ethanol is 100% pure?
A: Anhydrous calcium oxide or anhydrous calcium chloride is
add/put into the ethanol.
●
○
XXXXXXXXXXXXXXX
Thermometer
Fractioning
collum
Liebig
condenser
Water in
Water out
Product from
fermentation Porcelain
chips
Retort stand
with clamp
Distillate
(Ethanol)
Bunsen
burner
Rounded
conical
Water
Wire
gauge
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Q: What is the function of;
- thermometer
- porcelain chips
- Liebig condenser
A: thermometer is used to ensure that temperature is always
at 78 o
C.
B: Porcelain chips is used to avoid the solution jumped/
effervesence (breaking bubbles)
C: To cooled the ethanol vapour to become liquid.
Q: Named the process in Liebig condenser.
A: Condensation
Q: What is the properties of ethanol
A: Properties;
- colourless
- volatile
- good organic solvent
- miscible with water
- highly flammable
- antiseptic
- chemically reactive
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Q: What is the uses of ethanol
A: Uses;
- As a solvent in perfumes/cosmetics
- As a thinner in varnish, ink
- As a cleaner for compact disc.
- As a fuel for transport
- As a raw material for the manufacture of vinegar,
- As a raw material to make industrial product such as
antiseptic and cough syrup.
Industrial production of ethanol
Ethene is mix with steam is passed through concentrated
phosphoric acid (catalyst) at 300 o
C (temperature) and 60
atmosphere (pressure).
H3PO4
@ C2H4 concentrsted C2H5OH
CH2 = CH2 + H2O —————→ CH3CH2OH
300 o
C, 60 atm
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Chemical Properties
1. Combustion
i. Alcohol are very flammable sustances.
ii. Ethanol burns with non-smoky and blue flame and releases
lot of heat. Suitable for use as fuel, described as clean fuel.
Q: Write combustion equation for hexanol
2. Oxidation
i. Ethanol can be oxidised into ethanoic acid by an oxidising agent.
[Ethanoic acid is a family of carboxilic acids]
C2H5OH + 3O2  2CO2 + 3H2O
Ethanol Oxygen Carbon Water
dioxide
C6H13OH + 9O2  6CO2 + 7H2O
hexanol Oxygen Carbon Water
dioxide
CH3CH2OH + 2[O]  CH3COOH + H2O
Etanol Ethanoic acid
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Q: Show the structural formula for the equation above.
Q: Named 2 solutions are commonly used as oxidising agent.
(i) Acidified potassium manganate(VII), KMnO4
(purple to colourless / decolourised)
(ii) Acidified potassium dichromate(VI), K2Cr2O7
(orange to green)
Q: Draw a labeled diagram for the process.
H H H O
| | | ║
H — C — C — OH + 2[O] → H — C — C — OH + H2O
| | |
H H H
Heat
Ethanol +
potassium dikromat(VI) +
dilute sulfuric acid
Cold
water
Distillate
(ethanoic acid)
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Distillate (ethanoic acid)
- Colourless
- Vinegar smell
- Blue litmus paper turns red (acidic properties)
3. Dehydration
ALCOHOL → ALKENE
1. Converted ethanol into ethene and a molecule of water.
2. The elimination of water results the formation of a carbon-carbon
double bond.
3. Dehydration occur when
a. ethanol vapours is passed over a heated catalyst such as.
i- Porous pot / porcelain chips
ii- Purnice stone / aluminium oxide, Al2O3 /alumina
b. Ethanol is heated under reflux at 170 o
C with excess
concentrated sulphuric acid.
CH3CH2OH  CH2 = CH2 + H2O
Ethanol Ethene
- H2O
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Q : Draw the structural molecule for the process
Q : Draw labeled diagram.
Heat
Glass wool
soaked with
ethanol
Heat
Ethene
gas
Water
Porcelain
chips
Retort
stand
with
clamp
Test
tube
Delivery
tube
H H H H
| | | |
H — C — C — H → H — C ═ C — H + H2O
| |
H OH
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CARBOXILIC ACID
General formula CnH2n+1COOH
One hydrogen atom is replaced with functional
group – COOH
H O
| ║
H — C — C — OH
|
H
Formula: HCOOH
O
║
H — C — OH
Formula: CH3COOH
CARBOXYL GROUP
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Why families known as carboxylic ‘acid’
Carboxyl group plays a vital role to gives
acidic properties to carboxilic acid families.
CH3COOH H+
+ CH3COO-
Ethanoic
acid
Hydrogen
ion
Ethanoate
ion
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Molecular and Structural Formula
n Name
Molecular
formula
Mr
Structural
formula
0
Methanoic
acid
C0H2(0)+1COOH
= HCOOH
46
O
║
H — C — OH
1
Ethanoic
acid
C1H2(1)+1COOH
= CH3COOH
[C2H4O2]
60
H O
| ║
H — C — C — OH
|
H
2
Propanoic
acid
C2H2(2)+1COOH
= C2H5COOH
74
H H O
| | ║
H — C — C — C — OH
| |
H H
3
Butanoic
acid
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Naming carboxilic acids
Example 1:
C C COOHH
H
H
H
C
Longest continuous chains: propanoic acid
HH
H
Attached alkyl group: 2-methyl
Carboxyl carbon: carbon number 1
Name: 2-methylpropanoic acid
C4H8O2 / C3H7COOH
C C C
O
O H
H
H
H
H
Carbon number 123
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Example 2:
CH3 C COOH
H
C2H5
Longest continuous chains: butanoic acid
Carboxyl carbon: carbon number 1
Name: 2-methylbutanoic acid
Attached alkyl group: 2-methyl
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Example 3:
Example 4:
C3H7 C COOH
H
C2H5
Name: 2-ethyl pentanoic acid
C2H5 C COOH
H
C3H7
Name: 2-ethyl pentanoic acid
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Ethanoic Asid
Can be prepared through oxidation of an
ethanol.
Chemical equation:
This is carried out by refluxing ethanol with
an oxidising agent such as acidified potassium
dichromate(VI) or potassium manganate(VII)
solution.
H H
│ │
H — C — C — OH
│ │
H H
H O
│ ║
H — C — C — OH
│
H
+ 2[O] + H2O
K2Cr2O7 solutions
+
dilute H2SO4
reflux
CH3CH2OH + 2[O]  CH3COOH + H2O
Etanol ethanoic acid
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Preparation of ethanoic acid through refluxing
Condenser is used to prevent the loss of a
volatile liquid by vaporisation.
This method of retaining a volatile liquid
during heating is called refluxing.
How to carry out the activity?
Tissel tube
Water out
xxxxxxxxxxxxxx
Label the
diagram please
Water
in
Liebig condenser
Rounded bottom flask
Retort
stand
Absolute ethanol, C2H5OH +
Acidified potassium dichromate(VI),
K2Cr2O7 solution
Heat
Wire
gauge
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Physical Properties
- pH less than 7
- sharp or unpleasant smell
- turn moist blue litmus paper to red
- colourless liquid
Chemical Properties
Acid Properties
- Only hydrogen atom in the carboxyl group,
[-COOH] can ionize in water to produce
hydrogen ions, H+
.
Ethanoic acid is a weak acid. Why?
- it dissociates in water partially, most of
the molecules remain unchanged.
CH3COOH CH3COO-
+ H+
CH3COO-
Ethanoic
acid
Hydrogen
ion
Ethanoate
ion
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Reactions with metals
- Dilute ethanoic acid reacts with reactive
metal (Zn, Mg, Al) to produce a salt and
hydrogen gas.
2CH3COOH + Mg  Mg(CH3COO)2 + H2
Ethanoic acid Magnesium ethanoate
2CH3COOH + Zn  Zn(CH3COO)2 + H2
Ethanoic acid Zink ethanoate
6CH3COOH + 2Al  2Al(CH3COO)3 + 3H2
Ethanoic acid Aluminium ethanoate
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Reactions with bases
- Dilute ethanoic acid neutralizes alkalis such
as sodium hydroxide solution to give an
organic salt and water.
- Black copper(II) oxide powder dissolves in
dilute ethanoic acid.
CH3COOH + NaOH  CH3COONa + H2O
Ethanoic acid Sodium ethanoate
2CH3COOH + CuO  Cu(CH3COO)2 + H2O
Ethanoic acid Copper(II) ethanoate
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Reactions with carbonates
- Dilute ethanoic acid reacts with metal
carbonates to produce a salt, carbon dioxide
and water.
2CH3COOH + CaCO3  Ca(CH3COO)2 + CO2 + H2O
Ethanoic acid Calcium ethanoate
2CH3COOH + Na2CO3  2CH3COONa + CO2 + H2O
Ethanoic acid Sodium ethanoate
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Reactions with alcohols [Esterification]
Esterification:
Carboxilic acid reacts with alcohol to
produce an ester and water.
Concentrated H2SO4 : catalyst
[will discuss more in next chapter]
Concentrated
H2SO4
Carboxilic acid + Alcohol ——— Ester + Water
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Uses of carboxilic acid:
i. Ethanoic acid is known as acetic acids use in;
- Food flavoring
- Food preservatives
- To make drugs, dyes, paints insectisides,
plastics
- To make esters for use as slovents
ii. Methanoic acid is used to coagulate latex.
iii. Benzoic acids is used as food preservatives
iv. Fatty acids used in making soaps
v. Carboxilic acids use in the manufactured of
polyester and polyamids (fibres) in textile
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Conclusion on chemical reaction;
Carboxilic acid + reactive metal
 carboxylate salt + hydrogen
Carboxilic acid + base
 carboxylate salt + water
Carboxylate acid + metal carbonate
 carboxylate salt + carbon dioxide +
Water
Carboxilic acid + alcohol
 ester + water
1. Learning task 2.9 Summarizing pg 75
[notes book]
2. Effective Practise pg 75
1, 2, 3
[exercise book]
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ESTER
General formula CnH2n+1COOCmH2m+1
R : alkyl group in carboxilic acid
R’ : alkyl group in alcohol
O
║
CnH2n + 1C — OH + CmH2m+1OH
(carboxilic acid) (alcohol)
O
║
CnH2n + 1C — O — CmH2m+1 + H2O
(ESTER)
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Esterification
- Carboxilic acid reacts with alcohol to produce
ester and water.
- The functional group of ester is carboxilate
group.
- Concetrated sulphuric acid is catalyst.
- Carboxilic acid losses ‘OH’ and
- Alcohol losses ‘H’
- The bond that ‘break up’ will ‘rejoin’ again
CnH2n + 1 — C
O
O CmH2m+1
Break up
and rejoin
Carboxilate
group, -COO-
Derived from
carboxilic acid
Derived from
alcohol
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Naming Ester
- Name of ester consists of two parts, the name
of alcohol part is given first and followed by
the acid part.
Example: i. Ethanoic acid + methanol
 methyl ethanoate + water
Chemical equation:
H O
| ║
H — C — C — OH
|
H
CH3COOH
(Etanoic acid)
H
|
H— C — OH
|
H
CH3OH
(Methanol)
+
H O H
| ║ |
H — C — C — O — C — H + H2O
| |
H H
CH3COOCH3
(Methyl ethanoat) Water
CH3COOH + CH3OH → CH3COOCH3 + H2O
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Example: iii. Methanoic acid + Ethanol
 ethyl methanoate + water
Chemical equation:
O
║
H — C — OH
Methanoic acid
H H
| |
H— C — C — OH
| |
H H
Ethanol
+
O H H
║ | |
H — C — O — C — C — H + H2O
| |
H H
Ethyl metanoat Air
HCOOH + CH3CH2OH → HCOOCH2CH3 + H2O
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Q: Draw structural molecule of
i. Methyl metanoate
ii. Pentyl propanoate
iii. Propyl ethanoate
Solutions; i. Methyl metanoate
Methyl methanoate
H
|
H— C — OH
|
H
O
║
H — C — OH
MethanolMethanoic acid
Break up and rejoin
From alcoholFrom carboxilic acid
O H
║ |
H — C — O — C — H + H2O
|
H
methyl metanoate Air
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ii. Pentyl propanoate
Try now
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Preparation of ester through reflux
How to carry out this process?
[Success pg 378]
After boiling, Liebig condenser is rearranged
To carry out the fractional distillation at
74o
C – 78o
C to collect ethyl ethanoate.
XXXXXXXXXXXXXXX
Tissel tube
Liebig
condenser
Ethanol +
ethanoic acid +
concentrated
sulphuric acid
Porcelain chip
Water
bath
Water
in
Water
out
To prevent
bumping and
ensure smooth
boiling
To cold the
ethanol and
ethanoic acid
Uniform
heating
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Physical properties of ethyl ethanoate
- colourless
- fragrant smell
- insoluble in water
- lese dense in water
Natural Sources
- Most simple esters are found in fruits and
flowers.
ex: benzyl ethanoate in Jasmine
ethyl butanoate in pineapple
- Palm oil are liquid ester.
- The higher and complex ester does not
produce pleasant smells
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Uses of ester
- to make perfume, cosmetics
- to make artificial food flavoring
[Text Book: Table 2.8 pg 81]
- used as organic solvents
eg. ethyl ethanoate used in sunburn
lotion, polish removers, glues.
- to make synthetic polymers/fabrics
- to make aspirin (pain reliever)
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FATS
Fats and oils are chemically similar, but differ
in physical states.
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Fats : - found in animals
- solid in room temperature
- butter and tallow (types of fat)
Oil : - fats from plants
- liquid in room temperature
- palm oil, coconut oil, sunflower oil
- Fats and oil are mixtures of different esters.
- Fats are formed from 3 molecules of long-
chain carboxylic acids called fatty acids
with 1 molecules of alcohol called glycerol.
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H
│
H ― C ― OH
│
H ― C ― OH
│
H ― C ― OH
│
H
Fatty acids
- R1 , R2 , R3 contains
12 to 18 carbon
atoms per molecule
- R1 , R2 , R3 are three
alkyl groups which
may be the same or
different
- group: carboxilic acid
O
║
OH ― C ― R1
O
║
OH ― C ― R2
O
║
OH ― C ― R3
Glycerol
- propane-1,2,3-triol
- group: alcohol
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Formation of a fat molecule
H
│
H ― C ― OH
│
H ― C ― OH
│
H ― C ― OH
│
H
O
║
OH ― C ― R1
O
║
OH ― C ― R2
O
║
OH ― C ― R3
H O
│ ║
H ― C ― O ― C ― R1
│
│ O
│ ║
H ― C ― O ― C ― R2
│
│ O
│ ║
H ― C ― O ― C ― R3
│
H
+ 3H2O
+
Break up
and rejoin
Break up
and rejoin
Break up
and rejoin
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Importance of fats and oils
- energy
- nutrients
- thermal insulation
- protection to internal organ
[Text book: Figure 2.34 pg. 86]
Saturated and unsaturated fats
- Fat or oil molecules is affected by parent fatty
acids.
- Fatty acids can be differentiated in two ways;
i. the length of the carbon chains
(12 to 18 carbon atoms)
ii. saturated or unsaturated
Saturated fatty acid
- All carbon atoms joined together by
carbon-carbon single covalent bond.
- example:
Lauric acid (12 carbon atoms)
Palmitic acid (16 carbon atoms)
Stearic acid (18 carbon atoms)
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Unsaturated fatty acid
- The carbon chain has one or more
carbon-carbon double covalent bond.
Example:
i. Oleic acid: monounsaturated fatty acid
(one carbon-carbon double bond)-
[no of C = 18, DB = 9&10]
ii. Linoleic acid: polyunsaturated fatty acid
(two carbon-carbon double bond)
[no. of C = 18, DB = 9&10, 12&13]
iii. Linolenic acid: polyunsaturated fatty acid
(three carbon-carbon dauble bond)
[no. of C = 18, DB = 9&10, 12&13,
15&16]
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Saturated Fats
- Fats contain esters of glycerol and saturated
fatty acids.
- Example:
i. Tristearin ( glycerol + stearic acid)
ii. Tripalmitin (glycerol + palmitic acid)
Tristearin
H O
│ ║
H ― C ― O ― C ― (CH2)16 — CH3
│
│ O
│ ║
H ― C ― O ― C ― (CH2)16 — CH3
│
│ O
│ ║
H ― C ― O ― C ― (CH2)16 — CH3
│
H
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Tripalmitin
- Animal fats have large proportions of
saturated fats.
- They have high melting point and solids at
room temperature.
H O
│ ║
H ― C ― O ― C ― (CH2)14 — CH3
│
│ O
│ ║
H ― C ― O ― C ― (CH2)14 — CH3
│
│ O
│ ║
H ― C ― O ― C ― (CH2)14 — CH3
│
H
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Unsaturated Fats
- Fats contain esters of glycerol and
unsaturated fatty acids.
Example:
i. Triolein (glycerol + oleic acid)
- Plant or vegetable oils contain a large
proportions of unsaturated fats.
- They have lower melting points and are
liquids at room tempoerature.
H O
│ ║
H ― C ― O ― C ― (CH2)7 — CH ═ CH — (CH2)7 — CH3
│
│ O
│ ║
H ― C ― O ― C ― (CH2)7 — CH ═ CH — (CH2)7 — CH3
│
│ O
│ ║
H ― C ― O ― C ― (CH2)7 — CH ═ CH — (CH2)7 — CH3
│
H
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Converted unsaturated fats to saturated fats
- Unsaturated fats can be converted into
saturated fats by process called catalytic
hydrogenation.
The hydrogenation process is carried out by
bubbling hydrogen gas through hot, liquid
oil in the presence of fine particles of nickel
catalyst.
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Effect of fats on health
- Saturated fats (animal oil) will raise the level of
cholesterol.
- Cholesterol causes fatty deposites or the wall of veins or
arteries.
- Blood circulation is restricted and will raise the blood
presure
- Arteriosclerosis, can result in heart attack.
- Unsaturated fats (plant oil) do not contain cholesterol. Do
not cause cardiovascular problems.
Uses of palm oil
- Has many advantages.
- A cheaper, better and healthier oil.
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Natural Rubber
Natural rubber is a natural polymer.
Natural rubber is obtained from the latex
secreted by rubber tree.
Latex is a colloid. It consists of rubber
particles dispersed in water.
Natural rubber is poly(isopropene).
Its monomer is 2-metyhlbuta-1,3-diene or
isopropene. Each isopropene molecule
contains two pairs of double bonds.
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The isopropene molecules undergo addition
polymerization to produce a long-chain
molecule called poly(isopropene)
Each rubber particles is made up of many
long-chain rubber molecules, enclosed by a
protein-like membrane which is negatively
charged.
Negatively-charge
protein membrane
Long chain
rubber
molecules
Rubber
particle
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
Latex
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Polymerization of Isopropene
H CH3 H H
│ │ │ │
C ═ C ― C ═ C
│ │
H H
+
H CH3 H H
│ │ │ │
C ═ C ― C ═ C
│ │
H H
H CH3 H H
│ │ │ │
C ═ C ― C ═ C
│ │
H H
+
H CH3 H H
│ │ │ │
― C − C ═ C − C ―
│ │
H H
H CH3 H H
│ │ │ │
― C − C ═ C − C ―
│ │
H H
Isoprene
H CH3 H H
│ │ │ │
― C − C ═ C − C ―
│ │
H H
Repeated unit in polymer
polymerization
Isoprene Isoprene
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Coagulation process of latex
Rubber particle has negatively-charged protein
membrane.
The repulsion between the negatively-charged
particles prevents the rubber particles from coming
close to each other.
Latex could not coagulate.
Rubber particle
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
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Q: So what causes the latex to coagulate?
When an acid is added, the hydrogen ions, H+
neutralize the
negative charges on the protein membrane.
Q: Can you named the acid that usually used to coagulated
the latex in rubber industry?
A: Ethanoic acid also known as acetic acid.
[notes: all acid solutions can make latex coagulate]
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
─
+
+
+
++
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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Q: What do you think will happen next?
The rubber particles now come close together.
This enable them to collide with one another resulting in the
breakage of the protein membrane.
The rubber molecules/polymer combine with one another and
entangle.
Thus, causing the latex to coagulate.
EASY lah
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Q: The coagulation of latex will also occur if latex is exposed
to air. Why?
A: Bacteria from air can enter latex. The growth and spread
of bacteria produce lactic acid that causes the process
above.
Q: Named the substance can be used to preserve latex in
liquid state? Explain.
A: Ammonia, NH3.
NH3 solutions contains hydroxide ions, OH-
that
neutralised the acid/hydrogen ions, H+
produced by the
bacteria. The rubber particles remain negatively charged
and the coagulation is prevented.
[notes: all alkaly solutions also can be used]
Properties of natural rubber
- Soft
- Elasticity decreases over time.
- Easily oxidized by air.
- Sensitive to heat. When heated, it becomes sticky.
When cooled, it becomes hard and brittle.
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Vulcanization of rubber
Properties of rubber can be improved through vulcanization.
Vulcanization is a process whereby rubber is
reacted with sulphur to improved its properties.
Q: How the vulcanization process is carry out in industry?
A: 1st
method: Latex is heated with sulphur, or
2nd
method: Rubber products are exposed to disulphur
dichloride, S2Cl2.
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Q: Compare and contrast the properties of vulcanised and
unvulcanised rubber.
Similarities
Vulcanised and unvulcanised rubber is elastic, and
heat and electrical insulator
Differences [notes: draw a table]
Properties
Vulcanised
rubber
Unvulcanised
rubber
Elasticity More elastic Less elastic
Hardness Harder Softer
Tensile strength Stronger Weaker
Resistance to
heat
Can withstand
higher
temperature
Cannot withstand
temperature
Resistance to
oxidation
Less easily
oxidized
Easily oxidized
Effect of organic
solvent
Does not
become soft and
sticky easily
Become soft and
sticky easily
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Q: Why?
S
S
C
C
S
S
C
C
S
S
C
C
S
S
C
C
S
S
C
C
S
S
C
C
Rubber molecules
Cross-linkage of
sulphur atoms
vulcanisation
S
S
C
C
S
S
C
C
S
S
C
C
S
S
C
C
S
S
C
C
S
S
C
C
C═C C═C
C═C
C═C C═C
C═CC═C C═C
C═C
C═C
Natural rubber Vulcanised rubber
Bright Minds

11
A: Improved properties of vulcanised rubber is due to the
presence of cross-linkage of sulphur atoms between the
rubber molecules.
Q: How the cross-linkage of sulphur atom improve elasticity
and strength of the vulcanized rubber:
A: When vulcanised rubber is streched and released, the
cross linkage pull the chains back to their original
arrangement.
Q: Why vulcanized rubber more resistant to heat and organic
solvent?
A: The presence of sulphur cross-linkage increases the size
of rubber molecules.
Q: Why vulcanized rubber more resistant to oxidation?
A: Vulcanized rubber has much lesser carbon-carbon double
bond.
Bright Minds

12
Uses of natural rubber
Bright Minds

13
SPM Question (2006)
Diagram 2 shows the stretching phases of a vulcanised
rubber and an unvulcanized rubber strands.
Stretching
phases
Length of vulcanized
rubber
Length of
unvulcanized rubber
Before
During
After
Diagram 2
Plan an experiment to compare one characteristic shown in
Diagram 2 for both types of rubber.
Your planning should include the following aspects:
(a) Aim of the experiment
(b) All the variables
(c) Statement of the hypothesis
(d) List of substances and apparatus
(e) Procedure of the experiment
50 mm45 mm
60 mm59 mm
45 mm45 mm
Bright Minds

14
(f ) Tabulation of data [17 marks]
Vulcanized
rubber
45 59 14 45
unvulcanized
rubber
45 60 15 50
Bright Minds

SPM CHEMISTRY : Chapter 2 hydrocarbon

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SPM CHEMISTRY : Chapter 2 hydrocarbon