- Created by: Bobby
- Created on: 21-04-10 17:39
Alkanes are a family of Hydrocarbons. They are made from chains of carbon atoms surrounded by hydrogen atoms.
They only contain single covalent bonds.
1 Carbon Atom = Methane
2 Carbon Atoms = Ethane
3 Carbon Atoms = Propane
4 Carbon Atoms = Butane
alkane + oxygen (plenty) ---> carbon dioxide and water
Alkanes are relatively unreactive towards most chemicals. They don't react with substances dissolved in water. This is because the C-C and C-H bonds are unreactive.
Insoluble in water. Ethane has a boiling point of -103C. Methane and ethane are volatile and are gasses at room temperature.
Alcohols have an -OH Functional Group on the end of a standard alkane.The first two alcohols are: methanol and ethanol.
Ehtanol has a boiling point of 78C. Therefore it is a liquid at room temperature and evaporates easily making it volatile.
Methanol and Ethanol can dissolve many compounds that water cant. eg: hydrocarbons and oils. It is therefore a very useful solvent. It can also be used to make other organic chemicals.
These factor make it very useful for perfumes
Methylated spirit - is ethanol with chemicals such as methanol added.
Alcohols burn in air because they contain hydrocarbon chains.
Alcohol reacts with sodium: sodium + ethanol ---> sodium ethoxide and hydrogen.
Carboxylic Acids have an -COOH Functional Group on the end of a standard alkane. Their names end it (meth) -anoic acid.
Carboxylic acids react like any other acids. They are weak acids and react slowly. The salts fromed in the reaction end in (meth) -anoate.
Carboxylic acids react with metals to give a salt and hydrogen.
Carboxylic acids react with alkails to form salt and water.
Carboxylic acids react with carbonates to give a salt, water and carbon dioxide.
They have strong smells and tastes. If wine is left open in the air for a few days, the ethanol in the wine is oxidised to form ethanoic acid: causing it to taste like vinegar. This is because vinegar is a dilute from of ethanoic acid!
Carboxylic Acids have an -COOH- Functional Group on the end of a standard alkane.
alcohol + carboxylic acid <----> ester + water. This is know as esterfication.
They often smell sweet and fruity, and they are also volatile (evaporate easily: makes the smell spread) which makes them ideal for perfumes.
Esters are also used for flavourings, eg: apple, orange, banana etc. They are also used as solvents and plasticisers (make things more flexible)
Fatty Acids are Carboxylic Acids. They often have between 16 and 20 carbon atoms. Fatty acids can be saturated (only C-C single bond) or unsaturated (with C=C double bonds)
Plants and animals often make oils and fats to store energy. When an organism has more energy than it needs it stores some as fat, which they can use later.
Animal Fats: saturated hydrocarbon chains, normaly solid at room temperature.
Vegetable Oils: unsaturated C=C bonds, normaly liquid at room temperature.
Reflux, Distil, Purify, Dry.
Refer to P.72 of CGP Chemistry Revision Guide.
1 - Refluxing.
To make ethyl ethanoate you need to react ethanol with ethanoic acid. To speed the up the reaction such as a catalyst for example, concentrated sulphuric acid will work. Heating the mixture will also help. This is best done with a condenser which catches any vapour and recycles it - this is called refluxing.
2 - Distillation.
This stage separates the ester from anything else in the flask (eg. unreacted alcohol, carboxylic acid, sulfuric acid and water) The mixture is heated and the vapour goes up a fractionating column. When the top of the column reaches the boiling point of ethyl ethanoate, the liquid that flows out the condenser is impure ethyle ethanoate.
Making Esters - Continued.
3 - Purification
This stage removes any impurities. Sodium carbonate solution is shaken with the ester to remove any acidic impurities. These two do not mix, so the sodium carbonate can be removed. Then the remaining ester is shaken with concentrated calcium chloride to remove any ethanol. This is then removed. You are then left the the ester (ethyl ethanoate).
4 - Drying
Any water remaining in the ethyl ethanoate can be removed by shaking it with lumps of anhydrous calcium chloride, which absorbs the water.
Finally the pure ethyl ethanoate can be separated from the solid calcium chloride by filtration.