Presentation on theme: "KS4: Useful Products from Organic Sources"— Presentation transcript:
1KS4: Useful Products from Organic Sources ORGANIC CHEMISTRY
2Crude OilCrude oil is a mixture; it contains hundreds of different compounds, some small and some extremely large. Nearly all these compounds contain carbon and hydrogen only and are called hydrocarbons.Hydrocarbons are molecules that contain carbon and hydrogen only.The compounds present in crude oil are separated, processed and purified in an oil refinery. These processes are covered in the following slides.
3Composition of a typical crude oil Crude oils from different parts of the world have different composition
4It is difficult to obtain pure compounds from crude oil so instead, crude oil is separated intogroups of compounds called fractions. Eachfraction contains compounds of similar boiling point. A description of each fraction is shown below:
5Fractional distillation Crude oil is split into fractions using fractional distillation.Here crude oil is heated and pumped into the bottom of a tall tower containing trays. Compounds with low boiling points rise towards the top of the tower where they condense. Compounds with higher boiling point condense lower in the column. Thus each tray contains liquids (fractions) of different boiling point. The liquid on each tray is continuously pumped away.A fractional distillation tower works continuously, unlike distillation in the laboratory.
6How fractional distillation works 40°C 70°C Liquid out 180°C Very small molecules do not condense and come out of the topHow fractionaldistillationworks40°CSmall ones condense70°CShort ones condenseLiquid out180°CMedium ones condenseGetting cooler250°CLong ones condense340°CVery largemolecules do notvaporise and fallto the bottomCrude oilpreheater
7Uses of each fraction on next slide What fractional distillationproducesFuel gasPetrolFractionaldistillationseparates crudeoil according toboiling point.Uses of each fraction on next slideNaphthaKerosineGetting more volatileDiesel fuelFuel andlubricatingoilCrude oilBitumenpreheater
8Uses of each fraction Fuel gas Petrol / gasoline Naphtha Paraffin / Burned in the refinery to fuel the distillation process, sold as LPG, purified and sold as bottled camping gasFuel gasPetrol/ gasolineFuel for cars and motorcycles, also used to make chemicals.NaphthaUsed to make chemicals.Paraffin /KerosineFuel for greenhouse heaters and jet engines, manufacture of chemicals.Diesel fuelFuel for lorries, trains.Fuel andlubricatingoilFuel for the heating systems of large buildings, fuel for ships, lubricating oil.BitumenRoofing, and road surfaces.
9FractionNumber of carbon atomsFuel gas1-4, mostly 1.Petrol/ gasoline5-10Naphtha8-12.Paraffin /Kerosine10-16Diesel fuel14-22Fuel andlubricatingoil20-70BitumenMore than 65
10Burning HydrocarbonsThe apparatus below is used to test the products of combustion of a hydrocarbon.Suctionpumpice-waterCloudiness-indicates carbon dioxideCandle wax is thehydrocarbon hereLiquid collectedcan be tested withanhydrous cobalt chloridepaper (bluepink).any hydrocarbon + oxygen water + carbon dioxide
11AlkanesCarbon atoms are unusual in that they are able to form strong covalent bonds to each other. Therefore, carbon is able to form chains of atoms of different length and so make molecules of different size. There are many thousands of molecules containing C-C bonds. In this course you learn about two groups of these compounds, alkanes and alkenes.Alkanes are hydrocarbons (molecules containing carbon and hydrogen only) in which each carbon atom is covalently bonded to four other atoms via 4 single covalent bonds. The other atoms can be either carbon or hydrogen.
12Alkanes: Methane, CH4It is common in organic chemistry to show covalent bonds as single lines. This makes it easier to show how the atoms are connected.HHHCHCHHHHDisplayed formulaor graphical formula‘Dot and cross’ diagram
13Alkanes: Ethane, C2H6 Ethane is the simplest alkane containing a C-C bond.HHHCCHHHHHHCCHHH
14Alkanes H H C H methane, CH4 H H H ethane, C2H6 H C C H H H H H H H C propane, C3H8HHHH
16hexane, C6H14 H H H H H H H C C C C C C H H H H H H H and so on………… Noticethe carbon chainis not straightand so on…………
17General Formula, CnH2n+2 Alkane series of molecules methane, CH4 propane, C3H8General Formula, CnH2n+2butane, C4H10pentane, C5H12hexane, C6H14This is called ahomologous series.Since all these molecules contain only single covalent bonds, alkanes are called saturated.
18Increasing melting and boiling point. Physical Properties of the AlkanesThe alkanes show a gradual change in meltingand boiling points.Increasing melting and boiling point.
19Cracking The demand for some hydrocarbons is high and cannot be supplied from fractional distillation alone. To boost the amount of some smaller hydrocarbons produced some of the high boiling point fractions are converted to more useful hydrocarbons. This process is called cracking.Cracking involves breaking C-C bonds.ethenepressurecatalystDistillationtowerHeat tovaporiseLong alkanesmaller alkane
20CrackingOn the surface of the catalyst, long chain molecules are split apart or ‘cracked’. The reaction is:OctaneHeatpressurehexanecatalystethene+Etheneis usedto makeplasticsC8H18 C6H14 + C2H4
21CHEMICAL REACTIONS OF ALKANES Alkanes are generally unreactive. This is because they only contain C-H and C-C bonds.However, the lower members of the series readily combust in air. With plenty of air, the products are water and carbon dioxide only.Methane + oxygen water + carbon dioxideCH O 2H2O CO2Combustion with limited amounts of air, however, producescarbon monoxide and water. Carbon monoxide is a poisonous gas.
22ExtensionIsomerismAlkanes of the same molecular formula can have different arrangements of atomsThese molecules are isomers of butane
23AlkenesCarbon atoms can also form double covalent bonds to each other. Molecules with a double bond are called alkenes.HHHHCCCorCHHHHEthene is the simplestalkene.C2H4
24CnH2n Alkenes Alkenes have the general formula Alkenes are unsaturated because they contain a double C=C bond. In all alkenes at least two carbon atoms are joined to only 3 atoms.
26CHEMICAL REACTIONS OF ALKENES The double bond allows alkenes to undergo reactions where atoms are added to the molecule. Thus, alkenes are more reactive than alkanes.An addition reaction:Br2+If ethene is bubbled through bromine water the solution becomes colourless - this is used as the test for an alkene.Explanation: bromine colours the solution orange, however, this is used up in the reaction and the product is colourless.
27PolymerisationAlkenes can undergo addition reactions to other alkene molecules. The result is very long chains of carbon atoms called polymers.PressurehightemperaturecatalystAndlotsmore..This is written as:poly(ethene)PressurehightemperaturecatalystnnetheneThis is called addition polymerisation
28Examples of addition polymers Poly(propene)nnpropenenntetrafluoroethanePoly(tetrafluoroethane)or PTFE
321.i) How is crude oil split into fractionsii) Name the seven fractions produced by fractionaldistillation of crude oil.iii) Give three differences between fractions.2.i) What is meant by cracking?ii) Complete the formula below:C8H18 C2H4iii) The starting hydrocarbon is octane, name the two products of this reaction.iv) Describe how you could test for the presence of ethene.
333.i) Draw the bonding diagram for methane (show only outer shell electrons, carbon has an atomic number of 6).ii) Draw the graphical formula for methane.iii) Methane is saturated, explain what this means.iv) Draw the graphical formula for another alkane containing five carbon atoms.4. Propane is used as ‘Calor Gas’. Complete the word and equation for its combustion in the plenty of airPropane + Oxygen _________ + _________C3H O2 _____ ___Why is it necessary to combust hydrocarbons in plenty ofair?
345.i) In a homologous series the physical properties change gradually in the same direction. Plot a graph of boiling point against number of carbons for the alkanes. Use this graph to predict the boiling point of decane, C10H22.6.i) Write down the graphical formula for propene.ii) Write down the equation for the reaction of propenewith bromine.iii) Predict the reaction of propene with hydrogen and write down the equation.Iv) What type of reaction is this?
357.Using the polymerisation of ethene as an example, explain the term addition polymerisation.
36Harder Questions8. Draw graphical formula for the three isomers of pentane.9. Draw graphical formula for three isomers of butene.10. Write down the equation for the combustion ofpropene in plenty of air and with a restricted amount of air.
381.i) Crude oil is split into ‘fractions’ of different boiling point by fractional distillation. Here crude oil is vaporised and passed into a fractionating tower. Towards the top of the tower, where it is cooler, compounds of low boiling point condense and are collected on trays from which they are removed. Lower in the tower, higher boiling point fractions are collected.ii) Refinery gas / Petrol or gasoline / Naphtha / Kerosine or paraffin / Diesel / Oil / Bitumeniii) boiling point / viscosity / colour / size of hydrocarbon molecule
392.i) Cracking is the process used to convert long hydrocarbon molecules into smaller ones. The hydrocarbon liquid is vaporised and passed over a catalyst. On the surface of the catalyst the carbon chain is split to produce ethene and a smaller alkane.ii)C8H18 C6H14 + C2H4iii) C6H14 is hexane, C2H4 is etheneiv) You could pass the gas through bromine water. The bromine water, which is orange, will become colourless.
403i)ii)CHHHCHHiii) Methane is saturated because it contains no double bonds.iv)CHPentane, C5H12
414.Propane + Oxygen carbon dioxide + waterC3H O2 3CO H2OIn insufficient air/oxygen, carbon monoxide and waterare produced. Carbon monoxide is a poisonous gas.