Alkanes

• What is crude oil That is pumped from the Earth, or sea bed mostly made of

  A family of saturated hydrocarbons known as alkanes
• What is crude oil a mixture of?

  Many different alkanes of different chain length
• What is the most important use of hydrocarbons?

  Fuels
• What happens when hydrocarbons burn in air?

  The reaction is highly exothermic and releases, lots of energy, which is used if to fuel a wide range of vehicles
• Why can't crude oil be used as a fuel unless it is first purified


  It is a thick, viscous black liquid. It would be very difficult to ignite crude oil as it is difficult to vaporize and fuels must be in the vapor, phase to ignite.
• How is crude oil separated into fractions?

  Buy fractional distillation
• Properties of small molecules

  Low boiling point light in color easy to light runny
• Properties of large molecules

  High boiling point, dark in color, hard to light thick
• Order of fractions from small molecules to large molecules

  Refinery gas petrol, naphtha, kerosene diesel lubricating, oil, fuel oil, bitumen
• Mnemonic


  Run petro New king dead lying flat blood
• Refinery gas


  bottled gas for heating and cooking
• Petrol


  Petrol for vehicles
• naptha


  Making chemicals
• Kerosine


  jet fuel, paraffin for lighting and heating
• Diesel


  Diesel fuels
• Lubricating oil


  lubricating oils,waxes and polishes
• Fuel oil


  fuel for ships, factories and central heating
• Bitumen


  Roads and roofing
• Fractional distillation of crude oil

  Petroleum is heated to roughly 350°C

  at this temperature most of the hydrocarbons in the mixture boil and vaporize the hydrocarbons rise up the fractionating column

  as the fractionating column install. There is a temperature gradient. The bottom of the column is hotter than the top

  as the hydrocarbons rise they begin to cool as they get to the cooler part of the column

  each hydrocarbon has a different boiling point

  when a hydrocarbon reaches of boiling point and condenses as it is at its boiling point

  Each hydrocarbon condenses at a different point in the column leading to separate fractions being produced at different heights.
• Boiling point


  As the length of the carbon chain increases boiling point increases
• Flammability


  As the length of the Carbon chain increases, flammability decreases
• Viscosity


  As the length of the carbon chain increases, viscosity increases
• What is a fraction ?

  A fraction is a group of compounds with similar boiling points that condense at different heights in the fractionating column
• Homologous series


  A group of compounds with the same general formula all members of the homologous series do the same chemical reactions because they have the same functional group each successive members is larger than a CH2 Group
• Functional group


  Place in the molecule where is the reaction happens defines the molecule
• Alkanes are saturated or unsaturated?

  saturated
• Saturated


  Every carbon atom has made four single bonds
• Hydrocarbons


  Compounds made of carbon and hydrogen only
• Alkanes


  methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane
• How to find structural formula


  Draw the displayed formula and split it into sections of carbon and hydrogen

  Then write them in a row if two of the same are in the row, you can group them together
• General formula of Alkane

  CxH2x+2
• Homologous series


  A group of compounds that have the same general formula. They have similar chemical properties gradually changing physical properties as each successive member of the group gets longer by a CH2 portion.
• Isomers


  Molecules with the same molecular formula, but different structure
• How to draw isomers

  Try to have the same number of carbon and hydrogen atoms, and give it a different structure to name it. You have to look at the longest chain and for the prefix, you have to find the shortest pathway to get the part that is branching off.
• Combustion of alkanes


  alkane + oxygen -> carbon dioxide + water
• What is the environmental problem caused by complete combustion of alkane and all fossil fuels

  Global warming
• Which Alkanes is the most damaging for the environment?

  Octane ,produces more co2
• Incomplete combustion of alkanes

  Alkane + Oxygen —— Carbon Monoxide + Water
• When do alkanes do substitution reactions with halogens?

  Only if there is UV light, this is why this reaction is an example of a photo chemical reaction
• What happens the more halogen is present?

  The more hydrogen atoms will be substituted