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Alcohols and Carbonyls

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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 alcohols Aldehydes and Ketones Methanol

3 Ethanol C2H5OH Functional group -OH + -
Hydrogen bonding allows ethanol to dissolve in water, pH 7. b.p. 78 oC. This effect decreases in alcohols as the length of the hydrocarbon chain increases. H C C H H OH Hydroxyl group Ethanol is a good solvent, it behaves both like water and other hydrocarbon solvents. H O R - + Combustion of ethanol CH3CH2OH O2  2 CO H2O H = kJ mol -1 Ethanol 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. yeast C6H12O6  2CH3CH2OH CO 2 2. Hydration of Ethene (Industrial manufacture of Ethanol) C2H 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.

5 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 feedstock In the production of vinegar, ether, chloroform and ethyl esters and ethene. Increasingly seen as an important fuel. Meths is ethanol with added methanol. Cars can use ethanol as a fuel. Fuel Others In thermometers (cheaper and safer than Hg and de-icers.

6 Dehydration of ethanol
Catalyst CH3CH2OH  C2H H2O Ethanol 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

7 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. C H OH C H OH propan-1-ol propan-2-ol

8 alcohol (alkanol) 4 C’s  butanol 2-methylbutan-1-ol H C OH CH3
Naming alcohols 1. Decide on the type of compound (ie. consider functional group) alcohol (alkanol) 2. Select the longest chain 4 C’s  butanol 3. 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 the C bonded to the OH group Secondary alcohol, 2 C’s joined to the C bonded to the OH group Tertiary alcohol, 3 C’s joined to the C bonded to the OH group CH3 C OH H propan-2-ol 2-methylpropan-2-ol

10 Other Alcohols 1. Cycloalkanol 2. Diols (dihydric)
Cyclohexanol is a secondary alcohol 2. Diols (dihydric) C OH 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.

11 Oxidation of Alcohols aldehyde 1st 2nd aldehyde acid ketone
C=O carbonyl group Primary alcohols can be oxidised in two stages, 1st Stage - Hydrogen is lost; 2nd Stage - oxygen is gained. C O H H + O R oxidation H2O aldehyde 1st 2nd O + C H R aldehyde acid oxidation R C R1 O ketone Secondary 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 group Aldehydes and Ketones CH3 C = O Propanone, nail varnish remover and is used in the making of perspex H C = O - + Methanal, 40% in water is formalin, and is used to make polymers CH3 H C = O Ethanal, It’s trimer (CH3CHO)3 is used as a sleep inducing drug. It also causes a hangover CH3CH2 CH3 C = O Butanone, is a solvent used to make VHS tapes. Butan-2-one C4H8O

13 Aldehydes and Ketones RSC video on silver mirror 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.

14 Methanol, Steam reforming
The steam used must be pure. Carbon steam  Carbon monoxide hydrogen 1. Coal 1000 oC synthesis gas Methane steam  Carbon monoxide hydrogen 2. Natural Gas (UK) 900 oC Ni Catalyst 30 Atmos synthesis gas Methanol 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
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 Formalin, preserve biological specimens Polymers Polymethanal, machine parts Melamine, Electrical insulators Phenol methanal, heat resistant are all thermosettings plastics

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