C10.3 - Reactions and uses of alcohols

• Alcohols are flammable. They undergo complete combustion in air to produce caron dioxide and water. Methanol, ethanol, propanol and butanol are all soluble in water. Their solutions have a neutral pH. They also react with sodium. One of the products of this reaction is hydrogen.
• Alcohols can be oxidised by reacting with oxygen (e.g. from the air) to produce carboxylic acid. Different alcohols form different carboxylic acids. For example, ethanol is oxidised to ethanoic acid.
• Alcohols are used as solvents and fuels. This is beacuse they can dissolve most things water can dissolve, but they can also dissolve substances that water cannot dissolve - e.g. hydrocarbons, oils and fats
• Ethanol can be made by fermentation. Ethanol is the alcohol found in alcoholic drinks such as wine or beer. It is usually made using fermentation.
• 1. Fermentation uses an enzyme in yeast to convert sugars into ethanol. Carbon dioxide is also produced. The reaction occurs in solution so the ethanol produced is aqueous.
  2. Fermentation happens fastest at a temperature of around 37oC, in a slightly acidic solution and under anaerobic conditions (no oxygen)
  3. Under these conditions, the enzyme in yeast works best to convert the sugar to alcohol. If the condition were different, for example a lower pH/higher temperature or higher pH/lower temperature, the enzyme cold be denatures or could work at a much slower rate.
• Fermentation equation:  Sugar →(yeast) ethanol + carbon dioxide