GCSE C3 Chapter 5

• Organic molecules form the basis of living things and all contain carbon atoms
• Bond covalently to form the "backbone" of many series of organic molecules

• Series of molecules which have a general formula are called homologous series

• Alcohols - Functional group -O-H - 

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• Carboxylic acids - Functional group COOH

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• Esters - Functional group COO

• Alcohols with small molecules (methanol,ethanol,propanol) mix well with water and produce neutral solutions
• Many organic substances dissolve in alcohols making them useful solvents
• Ethanol is the main ingredient in beer, wine and other alcoholic drinks

• Alcohols burn in air to produce carbon dioxide and water
• Used as fuels - spirit burners, combustion engines, mixed with petrol
• Ethanol   + Oxygen  = Carbon dioxide +  water
• C2H5OH +    3O2     =       2CO2           3H2O

• They react with sodium to produce hydrogen gas and form a solution - reaction less vigorous than sodium with water

• Alcohols can be oxidised by chemical oxidising agents such as potassium dichromate to produce carboxylic acids

• Some microbes in the air can also oxidise solutions of ethanol to produce ethanoic acid which turns drinks sour and is the main ingredient in vinegar

• Carboxylic acids dissolve in water to produce solutions with a pH of less than 7
• Properties typical of all acids
• Carboxylic acids + carbonates = salt + carbon dioxide + water

• React with alcohols to produce esters
• Ethanol + ethanoic acid = ethyl ethanoate + water (Sulphuric acid catalyst)

• Carboxylic acids are described as being weak acids:
  • When strong acids dissolve in water to produce solutions they ionise compltely - the compound is broken down completley to produce H+ ions
  • HCl(aq) = H+(aq) + Cl-(aq)
  • When carboxylic acids dissolve in water the acid is not broken down completley, part of the comound remains
  • CH3COOH(aq) = CH3COO-(aq) + H+(aq)
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• Weak acids do not ionise completely in aqueous solutions

• Acids of the same volume - strong acids have a lower pH and react quicker

• All important organic chemicals that can be used in many ways: fuels, foods, drinks, solvents

• Advantages:
  • Can be used as fuels to save limited resources
  • Less polluting, carbon neutral

• Disadvantages:
  • Can be abused leading to health and social issues
  • Farmland used to grow crops used for production of fuels could be used for food

• Advantages and disadvantages for use of resources may change over time or when their are new developments and so monitoring and careful research is needed