Presentation on theme: "Alcohols and Carbonyls"— Presentation transcript:
1 Alcohols and Carbonyls Ethanol. Alkanol family, Aldehydes and Ketones. Methanol and Methanal
2 Index Ethanol Homologous series CnH2n+1OH Alcohol structures Oxidation of alcoholsAldehydes and KetonesMethanol
3 Ethanol C2H5OH Functional group -OH + - Hydrogen bonding allows ethanol to dissolvein water, pH 7. b.p. 78 oC.This effect decreases in alcoholsas the length of the hydrocarbon chain increases.HCCHHOHHydroxyl groupEthanol is a good solvent, it behaves both like water and other hydrocarbon solvents.HOR-+Combustion of ethanolCH3CH2OH O2 2 CO H2O H = kJ mol -1Ethanol can be used as a fuel in cars.
4 Ethanol C2H5OH Manufacture of Ethanol 1. Fermentation yeast Fermentation is used to make all alcohol based drinks.Any vegetable matter containing carbohydrates can be used.yeastC6H12O6 2CH3CH2OH CO 22. Hydration of Ethene (Industrial manufacture of Ethanol)C2H H2O CH3CH2OHCracking fractions from crude oil is a cheaper way to produce ethanol.(more expensive than making petrol)Reaction Conditions:300oC , High Pressure 60 Atm. , phosphoric acid catalyst.
5 Uses of EthanolDrinksEthanol is a natural product of fermentation. Ethanol cannot be more than 15% of the fermentation mixture, as ethanol is a poison and will kill the yeast.SolventIn varnishes (as it evaporates easily), dyes, perfumes anddrugs.ChemicalfeedstockIn the production of vinegar, ether, chloroform andethyl esters and ethene.Increasingly seen as an important fuel. Meths is ethanolwith added methanol. Cars can use ethanol as a fuel.FuelOthersIn thermometers (cheaper and safer than Hg andde-icers.
6 Dehydration of ethanol CatalystCH3CH2OH C2H H2OEthanolEtheneWhen hot ethanol is passed over aluminium oxideethene gas is produced.Ethene is very a very important chemical, it is the basisfor many plastics. E.g. Polythene
7 Homologous Series CnH2n+1OH Functional molecular structureMethanol, CH3OH; Ethanol C2H5OH; Propanol C3H7OHStraight chain isomers of AlkanolsPropanol C3H7OH, has 2 isomers, propan-1-ol and propan-2-ol.CHOHCHOHpropan-1-olpropan-2-ol
8 alcohol (alkanol) 4 C’s butanol 2-methylbutan-1-ol H C OH CH3 Naming alcohols1. Decide on the type of compound (ie. consider functional group)alcohol (alkanol)2. Select the longest chain4 C’s butanol3. Name the compound with the branched chains in ascending order.2-methylbutan-1-ol
9 Different types of alcohol Primary alcohol,1 C joined to theC bonded tothe OH groupSecondary alcohol,2 C’s joined to theC bonded tothe OH groupTertiary alcohol,3 C’s joined to theC bonded tothe OH groupCH3COHHpropan-2-ol2-methylpropan-2-ol
10 Other Alcohols 1. Cycloalkanol 2. Diols (dihydric) Cyclohexanol is a secondary alcohol2. Diols (dihydric)COHHEthane-1,2-diolAnti freeze3. Triols (Trihydric)e.g. propane –1,2,3,triol or Glycerol is used in cosmetics, paints andnitroglycerine explosives.
11 Oxidation of Alcohols aldehyde 1st 2nd aldehyde acid ketone C=O carbonyl groupPrimary alcohols can be oxidised in two stages,1st Stage - Hydrogen is lost; 2nd Stage - oxygen is gained.CO HH+ORoxidationH2Oaldehyde1st2ndO+CHRaldehydeacidoxidationRCR1OketoneSecondary alcohols can be oxidised to form ketones,Tertiary alcohols do not undergo oxidation.
12 Aldehydes and Ketones CHO alkanal functional group C=O ketone functional groupAldehydes and KetonesCH3C = OPropanone, nail varnish remover andis used in the making of perspexHC = O-+Methanal, 40% in water is formalin,and is used to make polymersCH3HC = OEthanal, It’s trimer (CH3CHO)3 is used as asleep inducing drug. It also causes a hangoverCH3CH2CH3C = OButanone, is a solvent used to make VHS tapes.Butan-2-oneC4H8O
13 Aldehydes and Ketones RSC video on silver mirror Distinguishing tests (Using mild oxidising agents.)Aldehydes are oxidised to carboxylic acids1. Fehlings solution contains Cu2+ ions (blue) which form Cu+ ion(orange-red) in the presence of aldehydes.2. Tollen’s reagent contains Ag+ ions, which form Ag in the presenceof aldehydes (silver mirror test)3. Acidified Potassium Dichromate orange Cr2O72-(aq) to green Cr3(aq)Ketones do not react with oxidising agents.
14 Methanol, Steam reforming The steam used must be pure.Carbon steam Carbon monoxide hydrogen1. Coal1000 oCsynthesis gasMethane steam Carbon monoxide hydrogen2. Natural Gas (UK)900 oCNi Catalyst30 Atmossynthesis gasMethanol is oxidised into methanal, either by:1. Zinc/Chromium oxide catalysts oC and Atm.2. Cu/Zn/Al oxide catalysts oC and Atm.CH3OH O2 HCHO + H20
15 Uses for Methanol and Methanal FuelAdded to ethanol to make meths, cleaner flame than hydrocarbons.Added to petrol octane number 114. MTBE (Methyl Tertiary Butyl Ester)Can be converted into petrol using Zeolite.Drugs and FabricsFormalin,preserve biological specimensPolymersPolymethanal, machine partsMelamine, Electrical insulatorsPhenol methanal, heat resistant are all thermosettings plastics