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AS and A Level: Organic Chemistry

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Five equations you must know for organic chemistry

  1. 1 Alcohol + carboxylic acid = ester + water (eg CH3OH + CH3CH2COOH becomes CH3OOCH2CH3 + H2O)
  2. 2 Alkene + hydrogen = alkane (eg CH2=CH2 + H2 becomes CH3CH3)
  3. 3 Alkene + water = alcohol (eg CH2=CH2 + H2O becomes CH3CH2OH)
  4. 4 Halogenoalkane + hydroxide ion = alcohol + halide ion (eg CH3Br + OH- becomes CH3OH + Br-)
  5. 5 Alkene + hydrogen bromide = halogenoalkane (eg CH2=CH2 + HBr becomes CH3CH2Br)

Five facts about alcohols

  1. 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. 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. 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. 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. 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. 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. 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. 3 Hydrocarbons are insoluble in water as they cannot make intermolecular forces with them.
  4. 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. 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
  1. Marked by a teacher

    Experiment to determine the ethanol content of wine

    5 star(s)

    From this, a graph of percentage ethanol solution against density was made. This graphs later compared to the density of the wine, so the percentage ethanol of the wine can be read off the graph. The samples of wine are then distilled, in order to extract the ethanol from the sample. Before distillation, the wine is made alkaline using Sodium Hydroxide. This is because the solutions of ethanol used in order to make the ethanol concentration against density calibration graph contained ethanol and water only, and it the sample of wine was not made alkaline then many of the volatile acids contained in the wine would distil off and affect results.

    • Word count: 2599
  2. Marked by a teacher

    Reactions of aldehydes and ketones. The purpose of this experiment is to compare some reactions of ethanal and propanone.

    5 star(s)

    About 2 cm3 of 2,4-dinitrophenylhydrazine was added into the test tube. 4. The experiment was repeated using propanone instead of ethanal. Part 3: Oxidation reaction (a) With acidified potassium dichromate 1. 5 drops of ethanal, 2 drops of potassium dichromate solution and 10 drops of dilute sulphuric acid were added into a test tube. 2. The test tube was shook gently and was put into a warm water bath. 3. The experiment was repeated using propanone instead of ethanal.

    • Word count: 2576
  3. Marked by a teacher

    Preparation of propanone from propan-2-ol

    5 star(s)

    Chromic acid features chromium in an oxidation state of +6. It is a strong and corrosive oxidising agent. Apparatus and chemicals: Apparatus: Quick-fit distillation setup, anti-bumping granules, thermometer, conical flasks, beakers, filter funnel, filter paper, iced water bath, 10cm3 measuring cylinder, triple beam balance, dropper, suction flask Chemicals: About 3 cm3 propan-2-ol, 3 cm3 concentrated sulphuric acid, deionized water, 4g potassium dichromate (VI), 2-4-dinitrophenylhydrazine (2,4-DNP), anhydrous calcium chloride Procedure: Part 1: Oxidation of propan-2-ol and distillation 1. About 4g of potassium dichrome solid and 10 cm3 deionized water were added to a conical flask and the flask was well shaken to allow the solid to dissolve.

    • Word count: 2193
  4. Marked by a teacher

    Comparing the enthalpy changes of combustion of different alcohols

    3 star(s)

    An example of exothermic reaction is: photosynthesis in plants where the energy comes from the sunlight. Energy cannot be destroyed but it can transfer from one form to another. The total energy of a system of reacting chemicals and surroundings remains constant. The value for exothermic enthalpy change is always a negative value as the energy is lost to the surroundings ?H = -890.3 KJmol-1 The standard conditions to compare the enthalpy changes of various reactions are temperatures, pressures, amounts and concentrations of reactants or products. The standard conditions are: * A pressure of 100kilopascals (102kPa)

    • Word count: 2298
  5. Peer reviewed

    An investigation into the efficiency of alcohols as fuels.

    5 star(s)

    and knowing all the bonds and structures of the two reactants in alcoholic combustion, it is relatively easy to calculate the total energy that will be given off by the alcohols when burnt; Alcohols No. of carbons C-H O-H O=O C-C C-O C=O O-H Enthalpy in kJ/mole Methanol 1 3 1 1.5 0 1 2 4 -658 Ethanol 2 5 1 3 1 1 4 6 -1276 Propanol 3 7 1 4.5 2 1 6 8 -1894 Butanol 4 9 1 6 3 1 8 10 -2512 Pentanol 5 11 1 7.5 4 1 10 12 -3130 These calculated values were made into a graph.

    • Word count: 2440

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