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Organic ChemistryPetroleum (also called crude oil) is a naturally occurring mixture of hydrocarbons (mainly alkanes).Natural gas is mostly made up of methane and other short-chain alkanes.Fractional Distillation of PetroleumPetroleum is separated into fractions by fractional distillation.Each fraction is a mixture of hydrocarbons which boils over a certain temperature range.A lighter fraction contains fewer carbon atoms and has a lower boiling point range than a heavier fraction.(a)Petroleum is heated in the furnace and vaporises.(b)In the fractionating column, the vapour cools and condenses as it rises up the column.(d)Smaller hydrocarbons with lower boiling points are collected at the top of the column.(e)Bigger hydrocarbons with higher boiling points are collected at the bottom of the column.Uses of Petroleum FractionsFractionUsepetroleum gasfuel for cooking and heatingpetrolfuel for vehiclesnaphthafeedstock (raw material) for the petrochemical industry kerosenefuel for aircraft engines, cooking and heatingdiesel oilfuel for engines in buses, lorries and trainslubricating oilfor lubricating machines; for making waxes and polishesbitumenfor paving road surfaces; for roofingA homologous series is a family of organic compounds with the same functional group and similar chemical properties. Naming of organic compounds1 carbon atom – meth2 carbon atoms – eth3 carbon atoms – prop4 carbon atoms – butAlkanesAlkenesAlcoholsCarboxylic acidsFunctional groupno functional groupcarbon-carbon double bondhydroxylcarboxylGeneral formulaCnH2n+2CnH2nCnH2n+1OHCnH2n+1COOH(n starts from 0)Chemical reactionsCombustionSubstitution with Cl2CombustionAddition with H21076265161925Addition with Br2Additional polymerisationCombustionOxidationReaction withmetalcarbonatebases408029469910Test for unsaturated hydrocarbons00Test for unsaturated hydrocarbonsOrganic compounds in the same homologous serieshave the same functional group;have similar chemical properties;show a gradual change in their physical properties down the series.Each member of the alkene homologous series differs from the next by a –CH2– unit.Alkanes and AlkenesChange in propertiesReasonMelting point and boiling point increaseAs the molecular size of alkanes increases down the homologous series, forces of attraction between the molecules increase. More energy is thus required to overcome the forces between the molecules.Viscosity increaseAs the molecular size of alkanes increases down the homologous series, stronger forces of attraction between the molecules. More difficult for the molecules to slide past one another, hence more difficult to flow.Flammability decreaseAs the molecular size of alkanes increases down the homologous series, the percentage of carbon in the alkane molecules also increases, hence alkanes become less flammable.Similarities and Differences AlkaneAlkeneSimilaritiesHydrocarbons (contains only hydrogen and carbon atoms only)364283962913Recall the properties of covalent molecules!00Recall the properties of covalent molecules!34550352883900Low melting and boiling points.Insoluble in water and soluble in organic solvents.2066337232410react with oxygen gas, O200react with oxygen gas, O21808384172085Undergo complete combustion to form carbon dioxide and water vapour.DifferencesContains only C–C (single) bonds SaturatedContains C=C (double) bonds UnsaturatedGenerally unreactiveReactiveUndergoes substitution reactionsCondition: Halogens (Cl2) in the presence of ultraviolet (UV) light94107054910UV light00UV light1437005132379chloromethane00chloromethaneCH4(g) + Cl2(g) CH3Cl(g) + HCl(g)Undergoes addition reactions(See next page for details of each reaction)Does not react with aqueous bromine Ob: Aqueous bromine remains brown.React with aqueous bromine Ob: Aqueous bromine changes from brown to colourless.Burns with less smoky flameBurns with smokier flameDoes not undergo polymerisationUndergoes addition polymerisation1.Hydrogenation(a)The addition of hydrogen to alkenes to form alkanes(b)Conditions: 200°C, nickel catalyst2. Bromination(a)The addition of bromine to alkenes to form bromoalkane(b)This reaction is used to test for presence of unsaturated hydrocarbons.Bromine is added to the carbon atoms with the double bond.+ Br2 Bromine is added to the second and third carbon MON MISTAKE!Bromine is added to the first and last carbon.+ Br2 Bromine is added to the second and third carbon MON MISTAKE!Bromine is added to the first and last carbon.3. Addition Polymerisation(a) The process of joining together a large number of monomers to form a polymer is called polymerisation.(b)Conditions: High temperature and pressure, catalystThe carbon–carbon double bonds of the monomers break. Each monomer forms single bonds with two other monomers. Eventually, they join to form the polymer.center6254 monomer polymer repeating unitEquation: Note how the terms monomer, polymer and repeating unit describe the different structure.00 monomer polymer repeating unitEquation: Note how the terms monomer, polymer and repeating unit describe the different structure.Fats and Oils Polyunsaturated fats or oils contain more than one C=C bond in their molecules.FatsOilsSolids at room temperature and pressureLiquids at room temperature and pressureContain mainly saturated fat moleculesContain mainly unsaturated fat moleculesOils will undergo addition with hydrogen to form fats.Plastics and Pollution1.Plastics are widely used in place of natural materials such as wood and leather as they are(a)relatively cheaper;(b)easily moulded into different shapes;(c)light, tough and waterproof;(d)durable (resistant to decay, rusting and chemical attack).2.Many plastics are non-biodegradable. This means that they cannot be broken down by micro-organisms such as bacteria in the soil.3.Improper disposal of plastics can cause air, water and land pollution.4.Many plastics are difficult to dispose of as they do not naturally decompose. When plastics are burnt, they give off poisonous gases.left17536800390715517589500200955917076700Cracking of long chain hydrocarbonsCracking is the breaking down of long-chain hydrocarbons into smaller hydrocarbons or hydrogen.Alkenes are obtained by cracking petroleum. broken porous pot containing Al2O3 and SiO2mixture of alkanes and alkenesglass wool soaked in liquid petroleumheatwaterbroken porous pot containing Al2O3 and SiO2mixture of alkanes and alkenesglass wool soaked in liquid petroleumheatwaterConditions: 1)High temperature (600°C)2)Catalysts: Aluminium oxide (Al2O3) or silicon dioxide (SiO2) Importance of CrackingCracking produces useful short-chain alkenes.For example, ethene and propene are used to make ethanol and plastics.Cracking produces hydrogen which is required in the manufacture of ammonia.Cracking converts hydrocarbons of higher molecular mass into smaller molecules which are in higher demand.AlcoholsAlcohols are volatile liquids at room temperature and pressure. As the number of carbon atoms increases, their boiling points increase but their solubilities decrease.Chemical propertiesAlcohols undergo complete combustion to produce carbon dioxide and water vapour. E.g.: C2H5OH(aq) + 3O2(g) → 2CO2(g) + 3H2O(g) Alcohols undergo oxidation to produce carboxylic acids. An example of an oxidising agent is acidified potassium manganate(VII). E.g.: C2H5OH(aq) + 2[O] CH3COOH(aq) + H2O(l) Colour change of purple to colourless will be observed.Producing EthanolAlcohol fermentation is a process in which yeast act on glucose in the absence of oxygen to produce ethanol and carbon dioxide gas.C6H12O6 (aq) 2C2H5OH(aq) + 2CO2(g)Conditions: 1) Yeast2) 37°C3) Absence of oxygenAbove 37°C, the enzymes (yeast) are denatured and fermentation stops. If oxygen is present, the ethanol produced will be oxidised to ethanoic acid.Carbon dioxide and a dilute solution of ethanol are produced. Ethanol is then extracted from the mixture by fractional distillation.The alcohol content in fermentation does not exceeds 15%. When alcohol content is too high, the enzymes in the yeast will also die and cause fermentation to stop.Carboxylic acidsCarboxylic acids have acidic properties because carboxylic acids dissociate to form hydrogen ions when dissolved in water.Carboxylic acids are weak acids because they dissociate partially.Chemical propertiesCarboxylic acids react with metals to produce a salt and hydrogen gas.Carboxylic acids react with carbonates to produce a salt, water and carbon dioxide gas.Carboxylic acids react with bases to produce a salt and water.AlkaneAlkeneAlcoholCarboxylic acid?1. Combustion3. Combustion8. Combustion2. Substitution with chlorineConditions: UV light?4. Addition with bromine?5. Addition polymerisationConditions: High temp. and pressure???6. Addition with hydrogenConditions: Nickel catalyst, 200 °C7. Addition with steamConditions: Phosphoric(V) acid catalyst, 300 °C9. Fermentation (forms ethanol)Conditions: Yeast, 37 °C, absence of oxygen???10. OxidationConditions: Oxidising agent (Acidified potassium manganate(VII)11. with metal12. with carbonate13. with baseLong chain hydrocarbonShort chain hydrocarbon14. CrackingConditions: 600 °C, Aluminium oxide/silicon dioxide?AlkaneAlkeneAlcoholCarboxylic acid?1. Combustion3. Combustion8. Combustion2. Substitution with chlorineConditions: UV light?4. Addition with bromine?5. Addition polymerisationConditions: High temp. and pressure???6. Addition with hydrogenConditions: Nickel catalyst, 200 °C7. Addition with steamConditions: Phosphoric(V) acid catalyst, 300 °C9. Fermentation (forms ethanol)Conditions: Yeast, 37 °C, absence of oxygen???10. OxidationConditions: Oxidising agent (Acidified potassium manganate(VII)11. with metal12. with carbonate13. with baseLong chain hydrocarbonShort chain hydrocarbon14. CrackingConditions: 600 °C, Aluminium oxide/silicon dioxide? ................
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