Chemistry Organic Compounds
Alcohols, Aldehydes, Carboxylic Acids, Ketones, Esters Halogenoalkanes and CFCs
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- Created by: Rachel Gregory
- Created on: 02-06-09 18:44
Alcohols
- Functional group: CnH2n+1OH
- Colourless, flammable liquids
- Made by the hydration of ethene in presence of phosphoric acid catalyst, temperature of 300C and pressure of 60 atm
- ethene + water --> ethanol
- or made by the anaerobic fermentation of glucose, catalysed by the enzyme zymase, found in yeast, at a temperature of 37C. An ethanol concentration of <14% can be produced, but at concentrations >14% the alcohol denatures the enzyme. Higher concentrations are produced by distillation.
- glucose --> ethanol + carbon dioxide
- Primary alcohols have 0 or 1 alkyl group bonded to the carbon atom with the OH group attached
- Secondary alcohols have 2 alkyl groups bonded to the carbon atom with the OH group attached
- Tertiary alcohols have 3 alkyl groups bonded to the carbon atom with the OH group attached
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Oxidation of Alcohols
- Partial Oxidation of Primary Alcohols to form aldehydes
- Ethanol + [O] --> ethanal
- the ethanol and oxidising agent is heated and the product is distilled off as it forms
- the oxidising agents are sodium dichromate (V) and concentrated sulphuric acid
- the oxidising agent is reduced, and changes from orange to colourless
- Complete Oxidation of Primary Alcohols to form carboxylic acids
- Ethanol + [O] --> ethanoic acid
- The ethanal and oxidising agent is heated under reflux conditions
- reflux is continuous evaporation and condensing of volatile reactants, so they are kept in contact for longer to speed up the reaction
- The oxidising agents are sodium dichromate (V) and concentrated sulphuric acid
- the oxidising agent is reduced, and changes from orange to green.
- Secondary alcohols oxidise once to form ketones
- Propan-2-ol + [O] --> Propanone + water
- The reactants are oxidised with sodium dichromate (V) and concentrated sulphuric acid
- Tertiary alcohols do not oxidise
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Aldehydes
Aldehydes:
- Contain the functional group of a carbon bonded to a hydrogen atom and double bonded to an oxygen atom
- e.g. Propanal: C2H5CHO
- Formed from the partial oxidation of primary alcohols
Carboxylic Acids:
- Contain the functional group of a carbon bonded to an oxygen bonded to a hydrogen and the same carbon double bonded to an oxygen
- e.g. Propanoic Acid:C2H5COOH
- Formed from the complete oxidation of primary alcohol
Ketones:
- Contain the functional group CH2C=OCH3
- e.g. propanone
- Formed from the oxidation of a secondary alcohol
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Esters:
- Contain the functional group CH2OC=OCH2
- e.g. methly salicylate and ethyl ethanoate
- Formed from alcohol + carboxylic acid --> ester
- CH3OH + C6H4OHCOOH --> C6H4(HO)COOCH3 + H2O
- the oxygen is removed from the carboxylic acid
- Esters are often aromatic
- Esters are named by: alcohol(-anol)yl carboxylic acid(-oic)oate
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Halogenoalkanes and CFCs
Halogenoalkanes:
- made from alkanes by radical substitution
- the reactivity of the halogenoalkane increases as you move down the halogen group
- Halogenoalkanes can be polymerise
- Thomas Midegeley developed CFCs in the late 1800s
CFCs:
- Low in reactivity and volatility and non toxic
- so they were used extensively in aerosols, refrigerants and in air con units
- Carbon-halogen bonds are very strong
- CFCs do not break down until they reach the stratosphere where UV radiation from the sun causes the bonds to break and Chlorine radicals to form:
- -Cl + Ozone --> ClO- + oxygen
- ClO- + atomic oxygen --> -Cl + oxygen
- Overall : Ozone + atomic oxygen --> 2 oxygen molecules
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- This causes ozone depletion, leading to holes in the ozone layer.
- Allowing harmful UV radiation to reach the lower atmosphere, increasing the prevalence of skin cancers.
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