SPM Chemistry Form 5 Notes

CARBON

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

IUPAC Nomenclature

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

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.

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.

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.

 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

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.

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

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

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)