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Hydrocarbons and Fuels

Hydrocarbons and Fuels. Alkanes, Alkenes, and Alkyne, Halogen derivatives, Aromatic Hydrocarbons, Petrol, Alternative fuels, . Index. Carbon chemistry introduction. Alkanes and Alkenes. Alkynes. Halogen derivatives, CFC’s. Aromatic hydrocarbons. Fuels.

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Hydrocarbons and Fuels

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  1. Hydrocarbons and Fuels Alkanes, Alkenes, and Alkyne, Halogen derivatives, Aromatic Hydrocarbons, Petrol, Alternative fuels,

  2. Index Carbon chemistry introduction Alkanes and Alkenes Alkynes Halogen derivatives, CFC’s Aromatic hydrocarbons Fuels

  3. Organic Chemistry, the Chemistry of Carbon Originally chemical compounds were divided into 2 classes: Inorganic or Organic Organic compounds were derived from living things. It was believed that they contained a ‘vital force’ and could not be made from inorganic compounds. Carbon has the ability toCATENATE, forming covalent bonds with its own atoms. H C C H

  4. HO Organic Chemistry Organic chemistry is basically the study of compounds containing carbon (with the exclusion of oxides and carbonates) There are so many compounds containing carbon that a whole branch of chemistry is devoted to their study. Organic molecules may be as simple as methane,CH4 or more complicated such as cholesterol

  5. Molecular formula C3H7 Alkanes and Alkenes Alkane general formula C n H 2n+2 Alkene general formula C n H 2n No C’s Name Structural formula Meth Eth Prop But Pent Hex Hept Oct 1 2 3 4 5 6 7 8 Straight Chain Branched Chains and unsaturated CH3CH2CH3 CH3 (CH2)2CH3 CH3CH2CH3 Condensed formula

  6. Naming Compounds of Carbon Alkanes • Identify the longest chain • Identify the ‘branches’ and name them. • Number the carbon atoms on the longest chain, at the end giving • the lowest numbers for the branches. • 4. Write the branches in alphabetical order. • 5. If there are more branches with the same name • use di, tri etc Alkenes • Identify the longest chain, that contains a double bond. • Identify the ‘branches’ and name them. • Number the carbon atoms on the longest chain, starting from • the end nearest the double bond. Pick the lowest number to • describe the position of the double bond. • 4. Write the branches in alphabetical order. • 5. If there are more branches with the same name • use di, tri etc

  7. H H H H H H H CH3 H H H H H CH3 C C H C C C C C C H H C C C C C C H H H CH2 H H H CH2 H CH2 H H H CH2 H CH3 CH2 CH3 CH2 CH3 CH3 Naming Organic Compounds 1. Decide on the type of compound (ie. consider functional group) alkane 10 C’s  decane 2. Select the longest chain 3. Name the compound with the branched chains in alphabetical order. 7-ethyl-3-methyldecane

  8. H C2H5 H = H C C C C C CH3 H H H H CH3 1.Decide on the type of compound (ie. consider functional group) alkene 2. Select the longest chain 7 C’s  heptene 3. Number the C atoms so that the functional group has the lowest number hept-2-ene 4. Name the compound with the branched chains in ascending order. 5,5-dimethylhept-2-ene

  9. H CH3 H H H H C C C C C H H Cl H H CH3 1. Decide on the type of compound (ie. consider functional group) halogen (chloroalkane) 2. Select the longest chain 5 C’s  pentane 3. Name the compound with the branched chains and halogen in alphabetical order. 3-chloro-2,2-dimethylpentane

  10. H H H H H H H H C C C H H C C C C H H CH3 H H H H H STRUCTURAL ISOMERISM There are two types 1. Chain isomerism.Here the isomers have different arrangements of carbon atoms or different chains. For example there are two compounds with the molecular formula C4H10 butane 2-methylpropane Here, you can see that 2-methylpropane has a side chain.

  11. H H H H H H H H C C C C C C H H H H Cl OH H H H H H H H H C C C C H H H H C C propan-1-ol propan-2-ol H H Cl OH H H 2. Position Isomerism.Here the isomers have the same carbon skeleton and functional group but the position of the functional group is different. 1-chloropropane 2-chloropropane

  12. + Br-Br Orange/red Reaction of Alkenes Reaction with Hydrogen, hydrogenation, an addition reaction + H-H Propene Propane Reaction with halogens, 1,2 dibromopropane colourless

  13. Reaction with Hydrogen Halides + H-I 2 -iodopropane Normally the H from the halide attaches to the C which already has the most hydrogen’s. or 1 -iodopropane

  14. H C C H + Ethene H2 H C C H Ethane + H C C H H2 H H Alkyne family CnH2n-2 Ethene C2H2 CaC2 + 2 H2O Ca(OH)2 + C2H2 Addition reactions with H2 similar to alkenes. but two stages are possible Ni Catalyst 150 oC 1st 2nd

  15. Chloroform Solvent for grease Degreasing agent Freon Paint Stripper Correcting fluid Gortex, Teflon Vinyl chloride Halogen Derivatives Halogenalkanes and Halogenalkenes CHCl3 CCl2=CCl2 CCl2F2 CCl4 CH3CCl3 CCl2H2 CF2=CF2 CH2=CHCl 2-bromo-2-chloro-1,1,1-trifluorethane Halothane Lava lamps, non-polar alkanes and chloroalkanes mixed with polar water.

  16. Halogen Derivatives, CFC’s Chlorofluorocabons CFC’s All CFC’s are very unreactive, are not flammable and not toxic. They are used as flame retardants. CCl2F2 The first refrigerant, and in aerosols. CCl3F Used as a blowing agent to make expanded foam Recently Hydrofluorocarbons have replaced some CFC’s. e.g. 1,1,1,2-tetrafluoroethane is used as a refrigerant.

  17. Chlorofluorocabons CFC’s U.V.light CCl2F + Cl CCl3F Cl + O3 ClO + O2 Ozone destruction O3 ClO + O Cl + O2 CFC’s are very stable, lasting for 100 years in the atmosphere. So over time, CFC’s can reach the stratosphere. Here, UV radiation attacks the CFC’s forming free radicals ( ) . Free radicals react with O3, the reaction is complex, but one Cl free radical can break down 1 million O3 molecules.

  18. Aromatic Hydrocarbons Benzene C6H6 F.A. Kekule proposed the original structure as a result of a dream. The first structures are unstable and the electrons delocalise to form a much more stable structure. Aromatic carbon molecules contain the benzene ring. Aliphatic carbon molecules contain the linear chains of carbon ring. Aromatic carbon molecules containing the benzene ring and aliphatic chains are called Arenes.

  19. Methylbenzene (toluene) 1,2 - dimethylbenzene Phenylethene (styrene) C6H5CH2CH 1,3 - dimethylbenzene Aromatic Properties CH3 CH3 CH3 CH3 CH=CH2 CH3 The benzene ring does not contain 3 double bonds, and so does not take part easily in addition reactions. It is insoluble in water, being non-polar. It burns with a smoky flame as carbon is produced. Aromatic compounds are used in dyes, herbicides, insecticides fungicides,

  20. Aromatic compounds Cl CHCCl3 Poly-aromatic hydrocarbons PAH Cl DDT dichlorodiphenyltrichloroethane COOH COOCH3 NHCOCH3 Aspirin 2-ethanoyloxybenzenecarboxcyclic acid OH Paracetamol 4-hydroxyphenylethanamide

  21. H CH3 H CH3 H H C C C C C H H CH3 H H H By products from the combustion of petrol are CO, CO2, NOx and unburned Hydrocarbons Petrol Long chain Hydrocarbons tend to burn unevenly in a car engine, causing ‘knocking’. Branched chained hydrocarbons burn more evenly, so prevent ’knocking’. The alkane 2,2,4,-trimethylpentane has good antiknock properties This also has a high octane rating, 100. Straight chain hydrocarbons have a lower octane rating, heptane has an octane number of 0. Benzene is 106. Unleaded petrol in UK has octane rating of 95. Petrol is a blend of different hydrocarbons and this can change depending on the season. In the winter you would need a petrol which was more volatile. Companies change their blend 3 or 4 times a year.

  22. Petrol Reforming, this is the process by which straight-chain alkanes undergo a chemical change to change them into new, smoother burning compounds. High temperatures, pressures and a catalyst are used. Branched-alkanes, cycloalkanes and aromatic compounds are produced. Hydrocracking, this takes place at high temperatures in the presence of hydrogen. Long straight chain hydrocarbons are changed into small branched chain and straight chain alkanes.

  23. Biogas Methane, produced by anaerobic respiration Ethanol Produced by fermentation, octane rating of 111 Methanol A liquid, made from steam and methane. Octane rating of 114, also ‘clean’ burning. Toxic and corrosive Hydrogen economy The dream fuel, but needs electricity to make it. Fuel Cells 2x more efficient than the internal combustion engine. Requires a source of hydrogen and oxygen. Alternative Fuels, biofuels

  24. Did you know? CFC’s where replaced by HFC’s which do not degrade the ozone layer. However, they are greenhouse gases 1200x more powerful than CO2. A fridge contains 0.67kg of HFC’s, equivalent to 800 kg of CO2 . For this reason, some fridges now use HC’s, such as butane and propane. These are only 3 to 4x as powerful a green house gas as CO2.

  25. Did you know? Methane is 23x more powerful a greenhouse gas as CO2. Sewage methane can replace the use of natural gas for the generation of electrical power. So why does burning biogas give a negative value?

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