Chemistry carbon compounds (1)


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Chemistry carbon compounds (1)

  2. 2. INTRODUCTION • General formula : CnH2n+1OH, n = 1, 2, 3, ....... • Functional group : Hydroxyl • First 4 alcohol : Methanol(CH₃OH), Ethanol(C₂H₅OH), Propanol(C₃H₇OH), Butanol(C₄H₉OH)
  3. 3. STRUCTURAL FORMULA Butan-1-ol Butan-2-ol
  5. 5. FERMENTATION • This method only applies to ethanol. • Fermentation is the chemical process which microorganism such as yeast act on carbohydrate to produce ethanol and carbon dioxide. • When yeast is added to sugar (example: glucose), fermentation occurs. During fermentation, the yeast produce an enzyme called zymase. The zymase enzyme breaks down the glucose molecules to simpler molecule, namely ethanol and carbon dioxide. • Yeast is killed by ethanol concentrations in excess of about 15%, and that limits the purity of the ethanol that can be produced.
  6. 6. PHYSICAL PROPERTIES OF ETHANOL • Solubility in water – all members in alcohol are very soluble in water (miscible with water). • Volatility – all alcohols are highly volatile. • Colour and Smell – alcohols are colourless liquid and have sharp smell. • Boiling and melting points – all alcohols in general have low boiling points (78°C).
  7. 7. CHEMICAL PROPERTIES OF ETHANOL • Combustion of alcohol Complete combustion of alcohol. C2H5OH + 3O2 –> 2CO2 + 3H2O • Alcohol burns with clean blue flames. Alcohol burns plenty of oxygen to produce carbon dioxide and water. This reaction releases a lot of heat. Therefore, it is a clean fuel as it does not pollute the air.) Other example: 2C3H7OH + 9O2 –> 6CO2 + 8H2O • Oxidation of ethanol In the laboratory, two common oxidising agents are used for the oxidation of ethanol which are acidified potassium dichromate(VI) solution (orange to green) and acidified potassium manganate(VII) solution (purple to colourless). C2H5OH + 2[O] –> CH3COOH + H2O Ethanol oxidised to ethanoic acid (a member of the homologous series of carboxylic acids – will be discussed in Part 6). Other example: C3H7OH + 2[O] –> C2H5COOH + H2O
  8. 8. • Removal of water (Dehydration) Alcohol can change to alkene by removal of water molecules (dehydration). It results in the formation of a C=C double bond. CnH2n+1OH –> CnH2n + H2O C2H5OH –> C2H4 + H2O • Two methods are being used to carry out a dehydration in the laboratory. • a) Ethanol vapour is passed over a heated catalyst such as aluminium oxide, unglazed porcelain chips, pumice stone or porous pot. • b) Ethanol is heated under reflux at 180°C with excess concentrated sulphuric acid, H2SO4. Other example: C3H7OH –> C3H6 + H2O
  9. 9. USES OF ALCOHOL • Alcohol as a solvent (cosmetics, toiletries, thinners, varnishes, perfumes). • Alcohol as a fuel (fuel for racing car, clean fuel, alternative fuel). • Alcohol as a source of chemicals (polymer, explosives, vinegar, fiber). • Alcohol as a source of medical product (antiseptics for skin disinfection, rubbing alcohol).
  10. 10. EFFECT OF MISUSE AND ABUSE OF ALCOHOL • Most alcohol are poisonous. Methanol very toxic. Small amounts can result in blindness. Drinking more than 30cm of methanol can lead to death of the drinker. • Excess drinking of alcohol can be very dangerous. If it used over a long period of time, ethanol destroys the tissues of liver (cirrhosis). • Ethanol is believed to destroy the brain cell slowly. This can result in a loss of memory. • Under the influence of alcohol, the drinker may feel happy and like to socialise. However, excessive drinking leads to drunkenness. • a) The liver cannot break down the large amounts of ethanol absorbed all at once. • b) The working of the nerves in our brain is affected by the higher concentration of ethanol in the blood. Thus, alcohol can lower our thinking ability. • c) Habitual drinking of alcohol is not healthy. • d) Alcohol can also affect the healthy growth of the brain for children consuming the drink. • Pregnant woman who drink may give birth to babies with smaller birth weight or even babies with birth defects.
  11. 11. THE END
  13. 13. CHEMISTRY A+