Organic Chemistry

• hydrocarbons
  • aromatics
  • aliphatics
    • cyclic
      • ✅ saturated (all single bonds)
        • ✅ cycloalkanes
      • unsaturated
        • cycloalkenes
        • cycloalkynes
    • chain
      • ✅ saturated
        • ✅ alkanes
      • unsaturated
        • alkenes
        • alkynes

alkenes §

• unsaturated hydrocarbon
• general formula $C_n{H}_{2n}$

criteria for geometrical isomerism §

• ✅ double bond between carbons (C=C)

• ✅ two different groups attached to $C_2$

• ___, ___ to $C_3$

• trans - across

• cis - straight

alkynes §

• 1 sigma bond

• two pi bond

• C2H2 + Br2 -> C2H2Br4

• H - C 三 C - H + 2Br2 -> H - C - C - H and then 4 Br idk how to draw idk

Arenes - very misleading name (as arenes doesnt react with bromine water, so not double bond) §

• benzene
• methylbenzene C7H8
• substitution reaction of benzene with pure bromine (Br2 (l))
  • C6H6 + Br2 -catalyst> C6H5Br + HBr

Biofuels §

• fuels made by living organisms or the waste that they produce is called biofuels. this includes:
  • biogas
  • bioethanol
• biofuels provides renewable energy source, unlike fossil fuels.
• less impact on environment than fossil fuels.
• produced by anaerobic fermentation of organic waste containing carbohydrates by bacteria.
• gas contains:
  • 40-70% methane
  • carbon dioxide
  • traces of hydrogen, nitrogen and hydrogen sulphide.
• biogas is currently used in several ways, including in the production of electricity, heating water for central heating systems and as fuels for buses.
• production of biogas can be ideal in remote areas lacking mains electricity or sewage systems. it not only produces a useful fuel but can also be used to get rid of large quantities of sewage or other organic waste material
• on a small scale, biogas digesters can be used to provide energy for individual families or farms.
• in parts of rural india cow dung is used to produce biogas for cooking.

ethanol based fuel §

• ethanol produced by the anaerobic fermentation of glucose by yeast is used to make fuels such as gasohol.
• it is successfully used as a fuel for cars in brazil and the usa. brazil produces ethanol from sugar cane, whereas the usa uses maize.
• gasahol normally contains 10% ethanol and 90% petrol. this allows gashol to be used in unmodified petrol engines.

ethanol production §

• ethanol is produced by carrying out the following steps:

1. glucose is obtained from either:
   • maize starch broken down into glucose by the action of carbohydrase enzymes
   • sugar cane juices
2. yeast are added to the glucose, they respire anaerobically, producing ethanol and carbon dioxide.
3. once fermentation is complete pure ethanol is obtained by distilling the mixture.

advantages biofuels §

• produce lower greenhouse gas emissions and particulates than conventional transport fuels.
• biomass is a renewable source of energy, therefore biofuels are a more sustainable form of energy as it will not run out.
• using biofuels instead of fossil fuels can also help to conserve the world’s non-renewable fuel resources.
• biofuels can also by cheaper to use for drivers, as governments often introduce schemes to encourage people to reduce their emissions.

disadvantages §

• biofuels not completely carbon neutral because energy is used in the production and transportation of the biofuel. this energy is often provided by fossil fuels.

extra §

• larger surface area alkane has higher boiling point (as larger surface area has higher dispersion forces)
  • eg pentane > methylbutane > 2,2-dimethylpropane in terms of boiling points.
  • larger surface area means it will have greater contact area between molecules.