2.organic chemistry

• Crude oil

  • finite resource found in rocks
  • Remains of an ancient biomass consisting mainly of plankton that was buried in Mud
  • Mixture of a very large number of compounds
• hydrocarbons

  • made up of hydrogen and carbon atoms only
• Alkanes

  • general formula: CnH2n+2
  • Methane / ethane / propane/ butane

  
• Fractional distillation

  • gases enter a fractionating column
  • In the column there’s a temperature gradient
  • Long hydrocarbons have high boiling points so they condense at the bottom
  • Short hydrocarbons have a lower boiling point , condense at the top of the column
• petrochemical uses 


  • fractions processed to produce fuels and feedstock for the petrochemical industry
  • used in modern lifestyle (petrol, diesel oil, kerosene, heavy fuel oil and liquified petroleum gases) from crude oil
  • modern lifestyle materials (solvent, lubricants, polymers, detergents) depends on petrochemical industry
  • vast array of natural and synthetic carbon compounds occur due to the ability of carbon atoms to form famillies of similar compounds
• properties of hydrocarbons

  shorter carbon chains

  • less viscous
  • low boiling point
  • more flammable
• cracking and alkenes

  • products of cracking include alkanes and alkenes
  • hydrocarbons can be cracked to produce smaller, more useful molecules
  • catalytic cracking (passing over a hot catalyst)
  • steam cracking (mixing with steam + heated to a very high temperature so thermal decomposition reactions can occur)
  • high demand for fuels with small molecules and so some of the products of cracking are useful as fuels
  • alkenes are used to produce polymers and as starting materials for the production of many other chemicals
• complete combustion

  • hydrocarbon + oxygen --> carbon dioxide + water

  releases energy

  carbon and hydrogen in the fuels are oxidised
• testing for alkenes

  • alkenes are more reactive than alkanes and react with bromine water
  • alkanes --> stays orange
  • alkene --> colourless
• alkenes

  • hydrocarbons with a double carbon - carbon bond
  • general formula : CnH2n
  • unsaturated as they contain fewer hydrogen atoms than the alkane with the same number of carbon atoms
  • eg. ethene , propene, butene , pentene

  butene

  
• reactions of alkenes : hydration

  • ethene + water (steam) --> ethanol
• reactions with alkenes : halogens

  • ethene + chlorine --> dicloroethane
• reactions with alkenes : hydrogenation

  • ethene + hydrogen --> ethane
• incomplete combustion

  • alkene + oxygen --> carbon + carbon monoxide + carbon dioxide + water
  • burns with a smokey flame
• alcohol

  • functional group - OH
  • general formula : CnH2n+1OH
  • eg, methanol , ethanol , propanol, butanol

  ethanol

  
• reactions of alcohol : oxidising agents

  • alcohol + oxidising agent --> carboxylic acid + water

  eg.

  • methanol --> methanol acid + water
  • propanol --> propanoic acid + water
• reactions of alcohol : combustion

  • combustion of alcohol --> carbon dioxide + water
• reactions of alcohol : fermentation

  • 30 degrees and anaerobic conditions
  • glucose --> (yeast) ethanol + carbon dioxide
  • aqueous solutions of ethanol are produced when sugar solutions are fermented using Yeast
• reactions of alcohol : water

  • soluble in water + form neutral solutions
• reactions of alcohol : sodium

  • methanol + sodium --> sodium methoxide + hydrogen
  • ethanol + sodium --> sodium ethoxide + hydrogen
• carboxylic acid

  • functional group - COOH
  • general formula - CnH2n+1COOH
  • eg. methanol acid , ethanoic acid, propanoic acid , butanoic acid

  propanoic acid

  
• reactions of carboxylic acids : water

  • partially ionise in aqueous = weak acid
  • high PH
• reactions of carboxylic acids : metal carbonate

  • produce salt + carbon dioxide + water

  eg.

  • ethanoic acid + sodium carbonate --> sodium ethanoate + carbon dioxide + water
• reactions with carboxylic acids : alcohol

  • esters (pleasant smell = used in food)