Download - 52258699 SPM Chemistry Form 5 Notes
CARBON
COMPOUNDS
Organic compounds
1. Hydrocarbons – organic compounds that contain hydrogen and carbon elements only.
2. Non-hydrocarbons – organic compounds that contain other elements (oxygen, nitrogen,
iodine, phosphorus)
3. Saturated hydrocarbons – only single bonded (Carbon-Carbon) hydrocarbons.
4. Unsaturated hydrocarbons – at least one double / triple bonded (Carbon-Carbon)
hydrocarbons.
5. Complete combustion – organic compounds burn completely which form CO2 and H2O.
6. Incomplete combustion – organic compounds burn with sufficient supply of O2 which
form C (soot), CO and H2O.
Homologous Series
Homologous series – is a group or family of organic compounds containing a particular
functional group and similar chemical properties
Carbon Compounds General Formula
Functional group
Alkane CnH2n+2 n = 1, 2, 3, … Carbon-carbon single bond
- C – C -
Alkene CnH2n n = 2, 3, 4, … Carbon-carbon double bond
- C = C -
Alcohol CnH2n+1OH n = 1, 2, 3, … Hydroxyl group
- OH
Carboxylic Acids CnH2n+1COOH n = 0, 1, 2 Carboxyl group
- COOH
Esters CnH2n+1COOCmH2m+1 n = 0, 1, 2, …
m = 1, 2, 3, …
Carboxylate group
- COO -
IUPAC Nomenclature – used to name organic compound.
Prefix + Root + Suffix.
1. Prefix – name of the branch or side chain.
Formula Branch or name of group
CH3 - methyl
C2H5 - ethyl
C3H7 - propyl
C4H9 - butyl
C5H11 - pentyl
2. Two or more types of branches are present, name them in alphabetical order.
Number of side chain Prefix
2 Di-
3 Tri-
4 Tetra-
5 Penta-
6 Hexa-
3. More than one side chains are present, prefixes are used.
4. Root – the parent hydrocarbon (the longest carbon chain).
Number of carbon atoms Root name Number of carbon atoms Root name
1 meth- 6 hex-
2 eth- 7 hept-
3 prop- 8 oct-
4 but- 9 non-
5 pent- 10 dec-
o The longest continuous (straight chain) carbon chain is selected.
o Identify the number of carbon.
5. Suffix – functional group.
Homologous series Functional group Suffix
Alkane - C – C - -ane
Alkene - C = C - -ene
Alcohol – OH -ol
Carboxylic acid – COOH -oic
Ester – COO – -oate
Alkanes
1. General formula: CnH2n+2. Where n = 1, 2, 3, … (n = number of carbon)
2. Alkanes are saturated hydrocarbon.
Name of alkane Molecular formula Name of alkane Molecular formula
Methane CH4 Hexane C6H14
Ethane C2H6 Heptane C7H16
Propane C3H8 Octane C8H18
Butane C4H10 Nonane C9H20
Pentane C5H12 Decane C10H22
3. Physical properties of alkanes
Name Molecular formula RMM Density(g cm-3
) Physical state at 25°C
Methane CH4 16 - Gas
Ethane C2H6 30 - Gas
Propane C3H8 44 - Gas
Butane C4H10 58 - Gas
Pentane C5H12 72 0.63 Liquid
Hexane C6H14 86 0.66 Liquid
Heptane C7H16 100 0.68 Liquid
Octane C8H18 114 0.70 Liquid
Alkanes with more than 17 carbon atoms are solid.
Solubility– insoluble in water but soluble in organic solvent
Density – less dense than water
Electrical conductivity –do not conduct electricity.
Boiling and melting points –low boiling points and melting points.
4. Chemical properties of alkanes
Combustion of alkanes
Complete combustion
CH4 + 2O2 –> CO2 + 2H2O
Incomplete combustion occurs when insufficient supply of oxygen
CH4 + O2 –> C + H2O
2CH4 + 3O2 –> 2CO + 4H2O
Substitution reaction of alkanes (Halogenation)
Substitution reaction is one atom or a group of atoms in a molecule is replaced by another
atom or a group of atoms.
Example:
CH4 + Cl2 –> HCl + CH3Cl (Chloromethane)
CH3Cl + Cl2 –> HCl + CH2Cl2 (Dichloromethane)
CH2Cl2 + Cl2 –> HCl + CHCl3 (Trichloromethane / chloroform)
CHCl3 + Cl2 –> HCl + CCl4 (Tetrachloromethane)
The rate of reaction between bromine and alkanes is slower than the rate of reaction
between chlorine and alkanes because chlorine is more reactive than bromine.
Alkene
1. General formula: CnH2n. Where n = 2, 3, 4 … (n = number of carbon)
2. Alkenes are unsaturated hydrocarbons
Name of alkene Molecular formula
Ethene C2H4
Propene C3H6
Butene C4H8
Pentene C5H10
Hexene C6H12
Heptene C7H14
Octene C8H16
Nonene C9H18
Decene C10H20
3. Physical properties of alkenes
Name Molecular formula RMM Density(g cm-3
) Physical state at 25°C
Ethene C2H4 28 0.0011 Gas
Propene C3H6 42 0.0018 Gas
Butene C4H8 56 0.0023 Gas
Pentene C5H10 70 0.6430 Liquid
Hexene C6H12 84 0.6750 Liquid
Heptene C7H14 98 0.6980 Liquid
Octene C8H16 112 0.7160 Liquid
Nonene C9H18 126 0.7310 Liquid
Solubility – insoluble in water but soluble in organic solvent
Density – less dense than water.
Electrical conductivity – do not conduct electricity.
Boiling and melting points –low boiling points and melting points.
4. Chemical properties of alkenes
Combustion of alkenes
Complete combustion
C2H4 + 3O2 –> 2CO2 + 2H2O
(Alkenes burn with sootier flames than alkanes. This is because the percentage of carbon
in alkene molecules is higher than alkane molecules)
Incomplete combustion occurs when insufficient supply of oxygen
C2H4 + O2 –> 2C + 2H2O
C2H4 + 2O2 –> 2CO + 2H2O
(The flame in the incomplete combustion of alkenes is more smoky than alkanes)
Polymerisation reaction of alkenes
Polymerisation is the reaction when small molecules (monomers) are joined together to
form a long chain molecules (polymer).
n (CH2 = CH2) –> -(- CH2 – CH2 -)-n
Hydrogenation Hydrogenation is the addition of hydrogen to alkenes
C2H4 + H2 –> C2H6 (catalyst: nickel/platinum and temperature: 180°C)
Addition of halogen (Halogenation) Halogenation is the addition of halogens to alkenes
C2H4 + Br2 –> C2H4Br2
In this reaction the brown colour of bromine decolourised to produce a colourless liquid.
Bromination is also used to identify an unsaturated
Addition of hydrogen halides Hydrogen halides are hydrogen chlorine, hydrogen bromide, hydrogen iodide and etc.
C2H4 + HBr –> C2H5Br (Bromoethane)
Hydration Alkenes can react with a mixture of alkene and steam pass over a catalyst (Phosphoric
acid, H3PO4). The product is an alcohol.
C2H4 + H2O –> C2H5OH
Additional of acidified potassium manganate(VII), KMnO4 The purple colour of KMnO4 solution decolourised immediately to produce colourless
organic liquid. Also used to identify the presence of a carbon-carbon double bond in a
chemical test.
Comparing of Alkanes and Alkenes
Physical Properties Alkanes Alkenes
Physical state Physical state changes from
gas to liquid when going down
the series.
Physical state changes from
gas to liquid when going down
the series.
Electrical conductivity Do not conduct electricity at
any state.
Do not conduct electricity at
any state.
Boiling points and melting
points
Low boiling points and melting
points
Low boiling points and melting
points
Density Low densities Low densities
Solubility Insoluble in water (soluble in
organic solvent)
Insoluble in water (soluble in
organic solvent)
Chemical Properties Alkanes Alkenes
Reactivity Less reactive Reactive
Combustion Burn in air and produce yellow
sooty flame.
Burn in air and produce yellow
and sootier flame compare to
alkanes.
Reaction with bromine solution No reaction. Decolourise brown bromine
solution.
Reaction with acidified
potassium manganate(VII)
solution
No reaction. Decolourise purple acidified
potassium manganate(VII)
solution.
Isomerism
Isomerism – existence of two or more compounds having the same molecular formula
but different structural formula
Isomer – compounds exhibiting the same molecular formula but different structural
formula
Alcohol
1. General formula: CnH2n + 1OH. Where n = 1, 2, 3 … (n = number of carbon)
2. Alcohols are non-hydrocarbons which contain carbon, hydrogen and oxygen atoms.
Name of alcohol Molecular formula of alcohol
Methanol CH3OH
Ethanol C2H5OH
Propanol C3H7OH
Butanol C4H9OH
Pentanol C5H11OH
Hexanol C6H13OH
Heptanol C7H15OH
Octanol C8H17OH
Nonanol C9H19OH
Decanol C10H21OH
3. Physical properties of alcohol
Name Molecular
formula
Melting point (°C) Boiling point (°C) Physical state at 25°C
Methanol CH3OH -97 65 Liquid
Ethanol C2H3OH -117 78 Liquid
Propanol C3H5OH -127 97 Liquid
Butanol C4H7OH -90 118 Liquid
Pentanol C5H9OH -79 138 Liquid
Solubility – very soluble in water
Volatility – evaporates easily at room temperature
Colour and Smell – colourless liquid and have a sharp smell.
Boiling and melting points – low boiling points
4. Chemical properties of alcohol
Combustion of alcohol
Complete combustion of alcohol.
C2H5OH + 3O2 –> 2CO2 + 3H2O
(Alcohol burns with blue flames. This reaction releases a lot of heat.)
Oxidation of ethanol
Two common oxidising agents are used for the oxidation of ethanol which are
- acidified potassium dichromate(VI) solution (orange to green)
- acidified potassium manganate(VII) solution (purple to colourless).
C2H5OH + 2[O] –> CH3COOH + H2O
Ethanol oxidised to form ethanoic acid
Dehydration
Alcohol can change to alkene by dehydration. It results in the formation of a C=C double
bond.
C2H5OH –> C2H4 + H2O
Two methods are being used to carry out a dehydration in the laboratory.
a) Ethanol vapour is passed over a heated catalyst such as aluminium oxide,
porcelain chips, or porous pot.
b) Ethanol is heated under reflux at 180°C with excess concentrated sulphuric acid,
H2SO4.
Carboxylic Acids
1. General formula: CnH2n+1COOH. Where n = 0, 1, 2, 3 … (n = number of carbon)
2. Carboxylic acids are non-hydrocarbons which contain carbon, hydrogen and oxygen atoms.
Name of carboxylic acids Molecular formula of alcohol
Methanoic acid(Formic acid) HCOOH
Ethanoic acid(Acetic acid) CH3COOH
Propanoic acid C2H5COOH
Butanoic acid C3H7COH
3. Physical properties of carboxylic acid
Name Molecular formula Boiling point (°C)
Methanoic acid(Formic acid) HCOOH 101
Ethanoic acid(Acetic acid) CH3COOH 118
Propanoic acid C2H5COOH 141
Butanoic acid C3H7COH 164
Solubility – generally in carboxylic acid (the less than four carbon atoms) are very
soluble in water and ionise partially to form weak acid.
Density – density of carboxylic acid increases down the series
Boiling points – relatively high boiling points than the corresponding alkanes.
Colour and Smell – colourless and pungent smell
4. Preparation of carboxylic acid
Oxidation of an alcohol
The oxidation of ethanol is used to prepare ethanoic acid.
C2H5OH + 2[O] –> CH3COOH + H2O
Carried out by refluxing* ethanol with an oxidising agent
- acidified potassium dichromate(VI) solution – orange colour turns to green
- acidified potassium manganate(VII) solution – purple colour turns to colourless
* reflux = upright Liebig condense to prevent the loss of a volatile liquid by vaporisation.
5. Chemical properties of carboxylic acid
Reaction with metals
Ethanoic acid reacts with reactive metals (copper and metals below it in the reactivity
series cannot react with ethanoic acid).
(K, Na, Mg, Al, Zn, Fe, Sn, Pb, Cu, Ag, Au)
2CH3COOH + Zn –> Zn(CH3COO)2 + H2
Reaction with bases & alkali (neutralization)
CH3COOH + NaOH –> CH3COONa + H2O
In this reaction, a salt (sodium ethanoate) and water are formed.
Reaction with carbonates
Ethanoic acid reacts with metal carbonates (calcium carbonate, magnesium carbonate)
2CH3COOH + CaCO3 –> Ca(CH3COO)2 + CO2 + H2O
In this reaction, a salt (calcium ethanoate), carbon dioxide and water are formed.
Reaction with alcohols (Esterification) Ethanoic acid reacts with alcohol
CH3COOH + C4H9OH –> CH3COOC4H9 + H2O (Concentrated H2SO4 is the catalyst)
In this reaction, an ester (colourless sweet-smelling liquid) butyl ethanoate and water are
formed.
Esters
1. General formula: CnH2n+1COOCmH2m+1. Where n = 0, 1, 2, 3 … and m = 1, 2, 3 … (n and m =
number of carbon)
2. Esters are non-hydrocarbons which contain carbon, hydrogen and oxygen atoms.
Alcohol + Carboxylic acid Molecular formula of ester Name of ester
Ethanol + Methanoic acid HCOOC2H5 Ethyl methanoate
Methanol + Ethanoic acid CH3COOCH3 Methyl ethanoate
Propanol + Ethanoic acid CH3COOC3H7 Propyl ethanoate
Ethanol + Propanoic acid C2H5COOC2H5 Ethyl propanoate
3. Physical properties of ester
Simple esters are colourless liquid and are found in fruits and flowers.
sweet pleasant smell.
insoluble in water but soluble in organic solvent.
less dense than water.
cannot conduct electricity.
The higher and more complex esters have higher boiling points and less volatile.
Fats
non-hydrocarbons which contain carbon, hydrogen and oxygen atoms.
belonging to the group in ester.
are formed from glycerol and fatty acids.
Name of fat Types of fatty acids
Lauric acid* Saturated
Palmitic acid* Saturated
Stearic acid* Saturated
Oleic oxide ** Unsaturated
Linoleic acid*** Unsaturated
Linolenic acid*** Unsaturated
* Saturated: C-C single bonds
** Unsaturated (monounsaturated): C=C double bonds
*** Unsaturated (polyunsaturated): C=C double bonds
1. Animal fats have higher percentage of saturated fats than unsaturated fats.
2. Plant oils have higher percentage of unsaturated fats than saturated fats.
3. Physical properties of fats
Types of fats Saturated Unsaturated
Bonding C-C single bonds C=C double bonds
Melting point higher lower
Sources animals plants
State at room temperature solid liquid
Fats (animal) in general are solids at room temperature and acted as:
protective cushion to protect the vital organ
provide energy and stored in body
carry Vitamin A, D, E, K (insoluble in water)
Fats (plant) are called oils. Oils are liquids at room temperature.
4. Chemical properties of fats
Unsaturated fats can be converted into saturated fats by hydrogenation (additional
reaction) in 180°C in the presence of nickel catalyst.
5. Effect of fats
High consumption of fatty food will results:
obesity
high blood pressure
arteries become hard and leading to heart problems and stroke
Natural rubber
Monomer: isoprene, 2-methylbuta-1,3-diene.
1. Structure of rubber molecule
Latex is colloid (35% rubber particles and 65% water).
Rubber particle contains rubber molecules which are wrapped by a layer of negatively-
charged protein membrane. Same charge of rubber molecules repels each other. This
prevent rubber from coagulate.
2. Coagulation process of latex
The process for the coagulation of latex is summarised as:
1. Acid (H+) neutralise the negatively-charged protein membrane.
2. The rubber molecules will collide one another after the protein membrane is neutralised.
3. Rubber molecules (polymers) are set free when the protein membrane is break down
4. Rubber molecules combine with one another (coagulation).
3. Natural coagulation process of latex
1. Latex is exposed to air without adding acid
2. Coagulation process occurs in slower pace due to the bacteria action (which produce acid)
4. Prevent coagulation process of latex
1. Alkaline / Basic solution is added to the latex. Example: ammonia (NH3).
5. Properties of natural rubber
elastic
cannot withstand heat (become sticky and soft – above 50°C; decompose – above 200°C;
hard and brittle – cooled)
easily oxidised (present of C=C)
insoluble in water (due to the long hydrocarbon chains)
soluble in organic solvent
6. Vulcanisation of rubber
Vulcanisation – process of hardening rubber and increases rubber elasticity by heating it with
sulphur or sulphur compounds.
7. Comparison of vulcanised rubber and unvulcanised rubber
Properties Vulcanised rubber Unvulcanised rubber
Double bonds Decreases (formation of sulphur cross-links) More number of double bonds
Melting point High (presence of sulphur) Low
Elasticity More elastic (sulphur cross-links prevents the
polymer chain or rubber from slipping past)
Less elastic
Strength and hardness Strong and hard Weak and soft (polymer chain of rubber will
break when rubber is over stretched.
Resistant to heat Resistant to heat Poor resistant to heat
Oxidation Resistant to oxidation (less number of double
bonds per rubber molecule)
Easily oxidised by oxygen (many double bonds
per rubber molecules)