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C7: Further Chemistry

C7: Further Chemistry. C7.2 Alcohols, carboxylic acids and esters. Organic Chemistry. Organic chemistry  is a sub-discipline in chemistry that involves the scientific study of the structure, properties and reactions of organic materials and compounds. Meeting the Alkanes.

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C7: Further Chemistry

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  1. C7: Further Chemistry

  2. C7.2 Alcohols, carboxylic acids and esters

  3. Organic Chemistry Organic chemistry is a sub-discipline in chemistry that involves the scientific study of the structure, properties and reactions of organic materials and compounds.

  4. Meeting the Alkanes The alkanes are hydrocarbons, containing only hydrogen and carbon

  5. The Alkanes Methane CH4 Propane C3H8 Ethane C2H6 Butane C4H10

  6. Why do we use alkanes?

  7. Burning alkanes If there is plenty of air, ie enough oxygen: Methane + Oxygen  Carbon dioxide + Water Can you write the balanced symbol equation? CH4 + 2O2  CO2 + 2H20 (g) (g) (g) (g) Did you remember state symbols?

  8. Alkanes and Aqueous Reagents H H H C C C H H Alkanes are unreactive towards aqueous reagents because they contain only C—C and C—H bonds, which are difficult to break and therefore unreactive H H H

  9. Functional Groups All of the characteristic properties of alcohols are due to the presence of this functional group. H H C C H O H H H Can you give the molecular formula, structural formula, stick diagram for methanol and ethanol? H H Ethanol Ethane

  10. Why do we need methanol and ethanol?

  11. Uses of alcohols C2H5OH CH3OH

  12. Burning Alcohols in Air Can you write out the word equation for the combustion of ethanol in air. Write out the balanced symbol equation Don’t forget state symbols Ethanol + Oxygen  Water + Carbon dioxide C2H5OH + 3O2 3H20 + 2CO2 (l) (g) (g) (g) Alcohols burn in air to produce carbon dioxide and water because of the presence of a hydrocarbon chain

  13. Why have I been using methanol and ethanol for the demonstrations?

  14. Physical Properties H H C O H Methanol H H H H H H H H H C C H C C C C C C The longer the hydrocarbon the stronger the intermolecular forces and therefore the higher the boiling point. Longer hydrocarbons are also less soluble in water as they behave more like an alkane and so float on top of water due to their low density O H Octanol H H H H H H H H

  15. Reactions with Sodium Remember this? Sodium with water Alcohols- Sodium sinks in alcohol and doesn’t melt, it will steadily give off hydrogen Alkanes- Do not react with Sodium Sodium with alcohol

  16. Quick Quiz so far • Draw the structural formula for butanol • Write the molecular formula for butanol • Draw the structural formula for hexane • Write the molecular formula for hexane • Write the molecular formula for an alkane with 25 carbon atoms. • How many bonds does oxygen make in methanol? 7. Give an example of a use for ethanol 8. Give an example of a use for methanol

  17. Butanol C4H10O Hexane C6H14 C25H52 2 Fuel/feedstock for synthesis/solvent/used in perfume Solvent, antifreeze, feedstock for adhesives and plastics

  18. How do we make ethanol? • What process do we use? It will be used in home brewing • Fermentation is a key process for obtaining ethanol. It is relatively cheap and requires wheat or beet sugar. • The process involves the anaerobic respiration of yeast at temperatures between 20 and 40°C and at pH 7.

  19. Why is there a limit on the strength of alcohol that can be made?

  20. Key Sugar Ethanol Making Alcohol X When the ethanol concentration gets too high it kills off the yeast cells

  21. So how do we make stronger alcohol?

  22. How do we obtain a concentrated solution? • Ethanol has a different boiling point to water. We can therefore separate water and ethanol using distillation.

  23. Give it a thought Can you balance this equation? C6H12O6 → CH3CH2OH+ CO2 C6H12O6 → 2 CH3CH2OH+ 2 CO2 Can you name the chemicals?

  24. Other ways to make ethanol Genetically modified E. coli bacteria can be used to convert waste biomass from a range of sources into ethanol Optimum conditions: Temperature remain between 25-37oC Optimum pH level needs to remain constant

  25. Other ways to make ethanol They introduce new genes into the E.colibacteria allowing it to digest all the sugars in the biomass and covert them into ethanol. Therefore we can use a wide range of biomass to make ethanol rather than staying as waste eg corn stalks. Feedstock

  26. Linking alkanes and alcohol It is also possible to convert ethane into ethanol Crude Oil undergoes fractional distillation Long chain hydrocarbons (alkanes) are vaporised then cracked using a catalyst and heat Any unreacted products can be recycled and fed through the system again The molecules are purified using fractional distillation producing ethene Ethene is then reacted with steam, at a high temperature and with a catalyst to produce ethanol

  27. Write out the Symbol Equation Ethene + Steam  Ethanol C2H4 + H20  C2H5OH (g) (g) (g)

  28. The UK is the world's largest producer of synthetic ethanol Why is this not a good fact?

  29. Make a table listing the advantages and disadvantages of each method of producing ethanol.

  30. Tackling the 6 marker Which method do you think has the largest impact on the environment? Give reasons for your answer.

  31. The Alkanes H H H H H C H C C C H H H H H H H H H H H H C C C C C H H H C H H H H H H H

  32. H H C O H • Make models with molymods H H H H H H H H H H H C C H O H C C H C C C C C C O H H H H H H H H H H H

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