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AS and A Level: Organic Chemistry
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Five equations you must know for organic chemistry
- 1 Alcohol + carboxylic acid = ester + water (eg CH3OH + CH3CH2COOH becomes CH3OOCH2CH3 + H2O)
- 2 Alkene + hydrogen = alkane (eg CH2=CH2 + H2 becomes CH3CH3)
- 3 Alkene + water = alcohol (eg CH2=CH2 + H2O becomes CH3CH2OH)
- 4 Halogenoalkane + hydroxide ion = alcohol + halide ion (eg CH3Br + OH- becomes CH3OH + Br-)
- 5 Alkene + hydrogen bromide = halogenoalkane (eg CH2=CH2 + HBr becomes CH3CH2Br)
Five facts about alcohols
- 1 Primary alcohols are oxidised into aldehydes and water, which are then oxidised into carboxylic acids. Secondary alcohols are oxidised into ketones and water. Tertiary alcohols cannot be oxidised.
- 2 Alcohols are oxidised by acidified potassium dichromate (H+/K2Cr2O7). This starts off orange and will turn green if it oxidises something (so with tertiary alcohols it will stay orange).
- 3 There are two ways of making alcohols: fermentation and hydration of alkenes. Fermentation is good because it uses renewable resources and does not take much energy, however it can only produce alcohol up to 14% before the yeast die.
- 4 Alcohols are soluble in water as they can make hydrogen bonds with the water. However, the “carbon chain” attached to the OH cannot interact with water and is insoluble. This means that alcohols become more insoluble the longer the carbon chain.
- 5 Alcohols have a very high melting and boiling point compared to alkanes of the same chain length. This is because they can form strong hydrogen bonds with each other that require a lot of energy to break.
Five facts about hydrocarbons
- 1 The longer the carbon chain the higher the higher the boiling point, as there will be more points of contact and stronger van der Waals forces.
- 2 The more branched the carbon chain the lower the boiling point, as the molecules will not be able to pack as close together and will have weaker van der Waals forces.
- 3 Hydrocarbons are insoluble in water as they cannot make intermolecular forces with them.
- 4 Hydrocarbons have low boiling and melting points as the only intermolecular forces that can hold them together are weak van der Waals forces which require little energy to break.
- 5 When processing crude oil (a hydrocarbon), the aim of the game is to get short, highly branched hydrocarbons. This will increase their volatility and make them a better fuel. We do this through: fractional distillation (sorts them into different sizes), cracking (splits long chains into short chains), isomerisation and reforming (makes the chains branched and cyclic).
- Marked by Teachers essays 7
- Peer Reviewed essays 13
Some nations (Australia, USA (Obama)) are reluctant to join because of the impact on their economies.(See Geog notes) The ozone layer The Ozone Layer absorbs much of the harmful ultraviolet radiation emitted by the sun, which, if it were to reach the Earth's surface unimpeded, would cause burning and skin cancer (also vitamin D :)) Ozone, O3 is constantly formed and broken down. An equilibrium with O2 and O* is present. Overall Equation: O3 ? O2 + O O3 + (UV Rad) --> O2 + O* O2 + O* --> O3 These two reactions would maintain a steady rate if undisturbed.
- Word count: 928
Once the solution had cooled 3.8g of p-acetamidophenol was added. Through the top of the condenser ethyl iodide (3.0cm3) was introduced to the pale green mixture and the mixture boiled at reflux temperature (20-25�). Ethyl iodide was obtained from a burette in the fume hood few minutes before its use, due to its flammable nature and harmful vapour. A darkening green colouration occurred while p-acetanilide dissolved changing through to brown and then yellow. Once the reflux was completed 40cm3 of water was added and the flask was left in ice for a few minutes to cool.
- Word count: 833
As this is a low critical temperature it makes critical carbon dioxide very easy to work with. Another useful feature of critical carbon dioxide is that when it is in its solvent form it is able to be altered by making slight adjustments to temperature and pressure. The phase diagram below of carbon dioxide shows us that its triple point ( where all states of carbon dioxide exist together)
- Word count: 514
Adding water to it gives a solution pale grey with green tinge. After dissolving the solutions turns clear with a green-grey colour and no precipitate. Prepare a solution of 6.0g of sodium ethanoate in 25cm3 of water in a conical flask. Sodium ethanoate is a white powder. It dissolves completely in water to give a colourless solution. Carefully add 2cm3 of ethanoic anhydride to the solution of phenylammonium chloride,and stir vigorously until all the ethanoic anhydride is dissolved. Ethanoic Anhydride smells of vinegar. Adding it to the phenylammonium chloride gives a solution with oily blobs with a sweet fruity smell.
- Word count: 813
Sodium hydroxide is a caustic soda and so is not very dangerous however regular safety precautions (goggles, labcoats and gloves) and care is still carried out to prevent spillages. Ethanol is highly flammable and dangerous substance as it contains methanol. Therefore, it should not come into direct contact with any flame. It is harmful it swallowed, inhaled or comes into contact with skin. Observations: Methyl benzoate is originally a transparent liquid however the addition of the sodium hydroxide, ethanol and anti bumping granules turns the liquid cloudy.
- Word count: 692