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C7 - Organic chemistry (Alkenes and their reactions: (Alkenes have a c = c…
C7 - Organic chemistry
Hydrocarbons:
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Hydrocarbons form homologous groups, these consist of Alkanes, Alkenes, Alcohols and carboxyl group.
Hydrocarbon properties change as they increase in length. 1. As the length of the hydrocarbon increases, it becomes more viscous
- The shorter the chain the more volatile the hydrocarbon is, this means that is will turn into a gas at a lower temperature. So the shorter the hydrocarbon chain, the lower the temperature at which that hydrocarbon vapourises and condenses.
- The shorter the carbon chain the more flammable the hydrocarbon is.
Alkanes:
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The alkanes are a homologous series, a group of hydrocarbons that react in the same way.
The first 4 most common alkanes are: Methane, Ethane, Propane and Butane.
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Fractional Distillation:
Crude oil is formed over millions of years, it is made up of dead organisms, mainly plankton, and over millions of years, the high temperature and pressure have caused it to turn to crude oil.
Crude oil is a non-renewable source of fuel and energy, it is finite. This means it will run out.
Crude oil is made up of many different hydrocarbons, the majority are alkanes. The different compounds can be separated by fractional distillation.
In the fractional distillation column, the crude oil is heated in order to separate the different. This occurs due to the different evaporation points of the fractions of crude oil. The different hydrocarbons are called fractions.
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Addition polymers:
Polymers are made up of lots of the same molecule joined together in a long chain. Polymers are formed from the addition of smaller molecules called monomers. This reaction is called polymerisation. Monomers are often alkenes.
Monomers have a c=c bond, this broken to allow the addition of 2 new bonds either side of the molecule in the straight chain polymer. Monomers must be unsaturated to allow polymerisation to occur.
Polymerisation representations can be reversed and unsaturated to find the monomer that reacted with the polymer.
Alcohols:
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General formula: CnH2n+1OH. First 4 alcohols are methanol, ethanol, propanol, butanol.
The first four alcohols have similar properties: Alcohols are flammable and undergo complete combustion in air. The first 4 are all soluble in water and have a neutral PH. React with sodium - product hydrogen. Alcohols can be oxidised to produce carboxylic acids. Alcohols are used as solvents and the first 4 are used as fuels.
Ethanol can be produced by fermentation of yeast - Fermenter can be used to ferment yeast and sugar into ethanol, fermentation occurs best at 37 degrees and with a slight acidity.
Carboxylic Acids:
Functional group -COOH. Homologous series all containing the -COOH. Names end in anoic acid. This is used in conjunction with the 4 alkane/kene names
Carboxylic acids react in the same way as other acids. When they react the create an "anoate". For example methanoic acid in methanoate.
Carboxylic acids can dissolve in water, when they do so they release h+ ions into the water. Weaker acidic solutions have a higher ph than stronger acids when ionising.
Esters: Made from carboxylic acids. Esters have the functional group -COO-. Esters are formed from an alcohol and a carboxylic acid. A catalyst is usually used. (Acidic catalyst). Ester = alcohol + carboxylic acids = ester + water. Must learn the ester ("Ethyl Ethanoate").
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