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 CO 2 and H2O. 6. Incomplete combustion – organic compounds burn with sufficient supply of O 2 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 Alkane

CnH 2n+2

Alkene

CnH 2n

Alcohol

CnH 2n+1OH

Carboxylic Acids

CnH 2n+1COOH

Esters

CnH 2n+1COOC mH2m+1

Functional group Carbon-carbon single bond n = 1, 2, 3, … -C–CCarbon-carbon double bond n = 2, 3, 4, … -C=CHydroxyl group n = 1, 2, 3, … - OH Carboxyl group n = 0, 1, 2 - COOH n = 0, 1, 2, … Carboxylate group m = 1, 2, 3, … - COO -

IUPAC Nomenclature – used to name organic compound. Prefix + Root + Suffix. 1. Prefix – name of the branch or side chain. Formula CH3 C2H5 C3H7 C4H9 C5H11 -

Branch or name of group methyl ethyl propyl butyl pentyl

2. Two or more types of branches are present, name them in alphabetical order. Number of side chain 2 3 4 5 6

Prefix DiTriTetraPentaHexa-

3. More than one side chains are present, prefixes are used. 4. Root – the parent hydrocarbon (the longest carbon chain). Number of carbon atoms 1 2 3 4 5

Root name methethpropbutpent-

Number of carbon atoms 6 7 8 9 10

o o

Root name hexheptoctnondec-

The longest continuous (straight chain) carbon chain is selected. Identify the number of carbon. 5. Suffix – functional group. Homologous series Alkane Alkene Alcohol Carboxylic acid Ester

Functional group -C–C-C=C– OH – COOH – COO –

Suffix -ane -ene -ol -oic -oate

Alkanes 1. General formula: C nH2n+2 . Where n = 1, 2, 3, … (n = number of carbon) 2. Alkanes are saturated hydrocarbon. Name of alkane Methane Ethane Propane Butane Pentane

Molecular formula CH4 C2H6 C3H8 C4H10 C5H12

Name of alkane Hexane Heptane Octane Nonane Decane

Molecular formula C6H14 C7H16 C8H18 C9H20 C10H22

3. Physical properties of alkanes Name Methane Ethane Propane Butane Pentane Hexane Heptane Octane

Molecular formula CH4 C2H6 C3H8 C4H10 C5H12 C6H14 C7H16 C8H18

RMM 16 30 44 58 72 86 100 114

Density(g cm-3) 0.63 0.66 0.68 0.70

Physical state at 25°C Gas Gas Gas Gas Liquid Liquid Liquid 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

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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 + CH 2Cl2 (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: C nH2n. Where n = 2, 3, 4 … (n = number of carbon) 2. Alkenes are unsaturated hydrocarbons Name of alkene Ethene Propene Butene Pentene Hexene Heptene Octene Nonene Decene

Molecular formula C2H4 C3H6 C4H8 C5H10 C6H12 C7H14 C8H16 C9H18 C10H20

3. Physical properties of alkenes Name Ethene Propene Butene Pentene Hexene Heptene Octene Nonene    

Molecular formula C2H4 C3H6 C4H8 C5H10 C6H12 C7H14 C8H16 C9H18

RMM 28 42 56 70 84 98 112 126

Density(g cm-3) Physical state at 25°C 0.0011 Gas 0.0018 Gas 0.0023 Gas 0.6430 Liquid 0.6750 Liquid 0.6980 Liquid 0.7160 Liquid 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)

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Polymerisation reaction of alkenes Polymerisation is the reaction when small molecules (monomers) are joined together to form a long chain molecules (polymer). n (CH 2 = CH2) –> -(- CH2 – CH2 -)-n

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Hydrogenation Hydrogenation is the addition of hydrogen to alkenes C2H4 + H2 –> C2H6 (catalyst: nickel/platinum and temperature: 180°C)

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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

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Addition of hydrogen halides Hydrogen halides are hydrogen chlorine, hydrogen bromide, hydrogen iodide and etc. C2H4 + HBr –> C2H5Br (Bromoethane)

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Hydration Alkenes can react with a mixture of alkene and steam pass over a catalyst (Phosphoric acid, H3 PO4). The product is an alcohol. C2H4 + H2O –> C2H5OH

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Additional of acidified potassium manganate(VII), KMnO 4 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 Physical state

Alkanes Alkenes Physical state changes from Physical state changes from gas to liquid when going down gas to liquid when going down the series. the series. Electrical conductivity Do not conduct electricity at Do not conduct electricity at any state. any state. Boiling points and melting Low boiling points and melting Low boiling points and melting points points points Density Low densities Low densities Solubility Insoluble in water (soluble in Insoluble in water (soluble in organic solvent) organic solvent) Chemical Properties Alkanes Alkenes Reactivity Less reactive Reactive Combustion Burn in air and produce yellow Burn in air and produce yellow sooty flame. and sootier flame compare to alkanes. Reaction with bromine solution No reaction. Decolourise brown bromine solution. Reaction with acidified No reaction. Decolourise purple acidified potassium manganate(VII) potassium manganate(VII) solution 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: C nH2n + 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 Methanol Ethanol Propanol Butanol Pentanol Hexanol Heptanol Octanol Nonanol Decanol

Molecular formula of alcohol CH3OH C2H5OH C3H7OH C4H9OH C5H11OH C6H13OH C7H15OH C8H17OH C9H19OH C10H21OH

3. Physical properties of alcohol Name Methanol Ethanol Propanol Butanol Pentanol    

Molecular formula CH3OH C2H3OH C3H5OH C4H7OH C5H9OH

Melting point (°C) Boiling point (°C)

Physical state at 25°C

-97 -117 -127 -90 -79

Liquid Liquid Liquid Liquid Liquid

65 78 97 118 138

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] –> CH 3COOH + 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: C nH2n+1 COOH. 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 Methanoic acid(Formic acid) Ethanoic acid(Acetic acid) Propanoic acid Butanoic acid

Molecular formula of alcohol HCOOH CH3COOH C2H5COOH C3H7COH

3. Physical properties of carboxylic acid Name Methanoic acid(Formic acid) Ethanoic acid(Acetic acid) Propanoic acid Butanoic acid    

Molecular formula HCOOH CH3COOH C2H5COOH C3H7COH

Boiling point (°C) 101 118 141 164

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] –> CH 3COOH + 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

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Reaction with bases & alkali (neutralization) CH3COOH + NaOH –> CH3COONa + H2O In this reaction, a salt (sodium ethanoate) and water are formed.

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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.

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Reaction with alcohols (Esterification) Ethanoic acid reacts with alcohol CH3COOH + C4 H9OH –> CH3COOC4H9 + H 2O (Concentrated H2 SO4 is the catalyst) In this reaction, an ester (colourless sweet-smelling liquid) butyl ethanoate and water are formed.

Esters 1. General formula: C nH2n+1 COOC mH 2m+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 Ethanol + Methanoic acid Methanol + Ethanoic acid Propanol + Ethanoic acid Ethanol + Propanoic acid

Molecular formula of ester HCOOC2H5 CH3COOCH3 CH3COOC3H7 C2H5COOC2H5

Name of ester Ethyl methanoate Methyl ethanoate Propyl ethanoate 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 Lauric acid* Palmitic acid* Stearic acid* Oleic oxide ** Linoleic acid*** Linolenic acid***

Types of fatty acids Saturated Saturated Saturated Unsaturated Unsaturated 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 Bonding Melting point Sources State at room temperature

Saturated C-C single bonds higher animals solid

Unsaturated C=C double bonds lower plants 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 negativelycharged 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. 2. 3. 4.

Acid (H +) neutralise the negatively-charged protein membrane. The rubber molecules will collide one another after the protein membrane is neutralised. Rubber molecules (polymers) are set free when the protein membrane is break down 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 Double bonds Melting point Elasticity

Vulcanised rubber Decreases (formation of sulphur cross-links) High (presence of sulphur) More elastic (sulphur cross-links prevents the polymer chain or rubber from slipping past) Strength and hardness Strong and hard Resistant to heat Oxidation

Resistant to heat Resistant to oxidation (less number of double bonds per rubber molecule)

Unvulcanised rubber More number of double bonds Low Less elastic Weak and soft (polymer chain of rubber will break when rubber is over stretched. Poor resistant to heat Easily oxidised by oxygen (many double bonds per rubber molecules)