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Alcohols and Carbonyls Ethanol. Alkanol family, Aldehydes and Ketones. Methanol and Methanal Index Ethanol Homologous series CnH2n+1OH Alcohol structures Oxidation of alcohols Aldehydes and Ketones Methanol Ethanol C2H5OH H H C H H Functional group -OH Hydrogen bonding allows ethanol to dissolve in water, pH 7. b.p. 78 oC. C H This effect decreases in alcohols OH Hydroxyl group as the length of the hydrocarbon chain increases Ethanol is a good solvent, it behaves both like water and other hydrocarbon solvents. R O H + + H O - H Combustion of ethanol CH3CH2OH + 3 O2 2 CO 2 + 3 H2O Ethanol can be used as a fuel in cars. H = - 1367 kJ mol -1 + Ethanol C2H5OH Manufacture of Ethanol 1. Fermentation Fermentation is used to make all alcohol based drinks. Any vegetable matter containing carbohydrates can be used. yeast C6H12O6 2CH3CH2OH + 2CO 2 2. Hydration of Ethene (Industrial manufacture of Ethanol) C2H4 + H2O CH3CH2OH Cracking 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. Uses of Ethanol Drinks Ethanol 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. Solvent In varnishes (as it evaporates easily), dyes, perfumes and drugs. Chemical In the production of vinegar, ether, chloroform and feedstock ethyl esters and ethene. Fuel Increasingly seen as an important fuel. Meths is ethanol with added methanol. Cars can use ethanol as a fuel. Others In thermometers (cheaper and safer than Hg and de-icers. Dehydration of ethanol Catalyst CH3CH2OH Ethanol C2H4 + H2O Ethene When hot ethanol is passed over aluminium oxide ethene gas is produced. Ethene is very a very important chemical, it is the basis for many plastics. E.g. Polythene Homologous Series CnH2n+1OH Functional molecular structure Methanol, CH3OH; Ethanol C2H5OH; Propanol C3H7OH Straight chain isomers of Alkanols Propanol C3H7OH, has 2 isomers, propan-1-ol and propan-2-ol. H H H H C C C H H H propan-1-ol OH H H H H C C C H OH H propan-2-ol H H H H H H C C C C H CH3 H OH 1. Decide on the type of compound (ie. consider functional group) 2. Select the longest chain 3. Name the compound with the branched chains in ascending order. Naming alcohols H alcohol (alkanol) 4 C’s butanol 2-methylbutan-1-ol Different types of alcohol H H H C C H OH C H H C C O H C C C H H C Secondary alcohol, 2 C’s joined to the C bonded to the OH group Primary alcohol, 1 C joined to the C bonded to the OH group O H H H C C C H OH H propan-2-ol Tertiary alcohol, 3 C’s joined to the C bonded to the OH group CH3 H CH3 C CH3 OH 2-methylpropan-2-ol Other Alcohols 1. Cycloalkanol H H H C H C H O C C H H Cyclohexanol is a secondary alcohol H H C H C H H 2. Diols (dihydric) H OH OH C C H H H Ethane-1,2-diol Anti freeze 3. Triols (Trihydric) e.g. propane –1,2,3,triol or Glycerol is used in cosmetics, paints and nitroglycerine explosives. C=O carbonyl group Oxidation of Alcohols Primary alcohols can be oxidised in two stages, 1st Stage - Hydrogen is lost; 2nd Stage - oxygen is gained. H 1st R C O oxidation H + O R O R C H + H2O aldehyde O H 2nd C H aldehyde + O oxidation O R C O H acid Secondary alcohols can be oxidised to form ketones, Tertiary alcohols do not undergo oxidation. O R C ketone R1 CHO alkanal functional group C=O ketone functional group Aldehydes and Ketones CH3 C=O CH3 + - H C=O H CH3 C=O H CH3CH2 CH3 C=O Propanone, nail varnish remover and is used in the making of perspex Methanal, 40% in water is formalin, and is used to make polymers Ethanal, It’s trimer (CH3CHO)3 is used as a sleep inducing drug. It also causes a hangover Butanone, is a solvent used to make VHS tapes. Butan-2-one C4H8O RSC video on silver mirror Aldehydes and Ketones Distinguishing tests (Using mild oxidising agents.) Aldehydes are oxidised to carboxylic acids 1. 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 presence of aldehydes (silver mirror test) 3. Acidified Potassium Dichromate orange Cr2O72-(aq) to green Cr3(aq) Ketones do not react with oxidising agents. Methanol, Steam reforming The steam used must be pure. 1. Coal synthesis gas 1000 oC Carbon + steam 2. Natural Gas (UK) Methane + steam Carbon monoxide + 900 oC Ni Catalyst 30 Atmos hydrogen synthesis gas Carbon monoxide + hydrogen Methanol is oxidised into methanal, either by: 1. Zinc/Chromium oxide catalysts 350-450oC and 200-300 Atm. 2. Cu/Zn/Al oxide catalysts 175-300oC and 40-100 Atm. CH3OH + O2 HCHO + H20 Uses for Methanol and Methanal Methanol Fuel Added 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 Fabrics Methanal Formalin, preserve biological specimens Polymers Polymethanal, machine parts Melamine, Electrical insulators Phenol methanal, heat resistant are all thermosettings plastics