C7 - Organic Chemistry

• What is crude oil formed from?

  Hydrocarbons
• What is a hydrocarbon?


  A compound made up of hydrogen and carbon atoms.
• What does saturated mean in relation to a hydrocarbon?

  Each carbon atom is linked to as many hydrogen atoms as possible - 4 bonds.
• What is the general formula for an alkane?

  Cn H2n + 2
• What are the first 4 alkanes

  Methane

  Ethane

  Propane

  Butane
• What does homologous mean?

  Similar in structure or origin.
• What is a homologous series?

  A homologous series is a group of organic compounds that have the same functional group and follow a similar structural pattern.
• What are the differences in features between long and short chain alkanes?

  Long: Higher boiling point, lower flammability , higher viscosity. Short: Lower boiling point, higher flammability , lower viscosity.
• Explain the process of fractional distillation of crude oil



  Hydrocarbons have different boiling points depending on their chain length.

  Crude oil is heated and enters into the fractioning column, which decreases in temperature as you go towards the top. As the evaporated crude oil rises, the vapour condenses at different fractions.

  Short chain hydrocarbons are found at the top of the column due to being held together by weak intermolecular forces.

  Long chain hydrocarbons are found at the bottom due to being held together by strong intermolecular forces.
• What is a fraction?


  A part of the crude oil.
• What fuels do we depend on from crude oil?


  Ship fuel, lubricating oils, diesel, petrol, chemicals, liquified petroleum gas
• What useful materials are produced by the petrochemical industry?


  Plastics, fuels, chemicals
• Why is there a large variety of natural and synthetic carbon compounds?


  Carbon's ability to form strong covalent bonds with other elements and with itself allows for a wide range of structures and properties in natural and synthetic compounds.
• How does the length of a hydrocarbon affect its use as a fuel?

  As longer chain hydrocarbons are harder to vaporise and turn into a gas than shorter chain hydrocarbons, more energy is needed to kick start combustion of them. As a result, short chain alkanes like methane combust very quickly and only need a small spark for ingition. Whereas long chain alkanes need much more energy to start combusting.
• What is cracking?

  An example of thermal decomposition where long chain alkanes can be broken down into shorter, more useful alkanes plus an alkene.
• What are the requirements for catalytic cracking?

  High temperature of 550 degrees and a catalyst
• What are the requirements for steam cracking?

  High temperature
• What are the products of cracking?

  The products of cracking are shorter hydrocarbon molecules.
• How to test for an alkene?


  Bromine water turns from brown / orange to colourless in the presence of an alkene, but remains brown / orange in the presence of an alkane.
• Why is cracking used?


  Shorter chain alkanes are better fuels.
• What are the alkenes produced from cracking used for?


  Chemicals
• How does modern life depend on the use of hydrocarbons?

  Transportation, electricity, heating, plastics.
• What is the general formula for an alkene?

  Cn H2n
• What are the first 4 alkenes


  Ethene

  Propene

  Butene
• What does the term unsaturated mean in relation to a hydrocarbon?


  Doesn't have all its bonds. Can react.
• What is a functional group?

  A functional group is a specific group of atoms within a molecule that is responsible for the characteristic chemical reactions and properties of that molecule.
• What is the functional group of an alkene?

  Double bond of carbon
• How do alkanes and alkenes differ in addition reactions?


  The functional group of alkenes allows them to undergo addition reactions. Alkanes can not as they are fully saturated.

  Addition reactions is where 2 molecules combine to form one larger molecule and no other products.

  
• How do alkenes react with hydrogen?

  Alkene + Hydrogen -> Alkane

  Called hydrogenation

  Needs a catalyst

  
• How do alkenes react with water (Steam)?

  Alkene + Water -> Alcohol

  Called hydration

  Needs temp about 300 degrees celcius

  
• How do alkenes react with halogen?

  Alkene + Halogen -> Halogenoalkane

  Usually spontaneous

  
• What is the functional group of an alcohol?

  Hydroxide
• What is the general formula for an alcohol?

  C n H 2n+1 OH
• What are the first 4 alcohols?

  Methanol

  Ethanol

  Propanol

  Butanol
• What happens when an alcohol reacts with sodium metal?

  Alcohol + Sodium -> Metal Alcohol oxide + Hydrogen
• What happens when alcohol burns in air?

  Complete combustion
• What are the products of complete combustion?

  The products of complete combustion are carbon dioxide (CO2) and water (H2O).
• What happens when alcohol is oxidised?

  Forms carboxylic acid
• What are the main uses for alcohol?

  Recreation, disinfectant, fuel, solvent.
• How is ethanol produced using fermentation?

  Glucose -> Ethanol + Carbon Dioxide

  Requires yeast, sugar, water, a warm temperature between 25 to 35 degrees and a reaction vessel that will allow carbon dioxide to escape but not allow oxygen to get in.