C7: Alkanes and Alcohol

Chemistry, Carbon Compounds: C7

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The Alkanes

The Alkanes

  • Molecules in the alkane family are hydrocarbons.
  • Consisting only of hydrogen and carbon.
  • Atoms with alkane molecules are joined together with single bonds.
  • This means the molecules are saturated.
  • Methane- simplest hydrocarbon molecule and the smallest of the alkane family: 1 carbon atom, 4 hydrogen atoms


(http://www.moorlandschool.co.uk/earth/Oil%20Refinery/methane_structure.gif)Methane molecule

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The Alkanes Cont.

  • Imagine the alkane molecules as being part of a family- next molecule in the series has a longer chain.
  • Each time one more carbon atom is added and two more hydrogen.
  • After methane comes ethane: C2H6.
  • Methane, ethane, propane, butane, pentane, hexane, heptane,octane, nonane, decane...


ethane structure.gif (2845 bytes) (http://www.moorlandschool.co.uk/earth/Oil%20Refinery/ethane_structure.gif)Ethane Molecule

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  • Alkanes are used as fuels: they burn in air & release C02 and H2O.
  • As chain length increases so does the boiling point.
  • Alkanes do not react with aqueous substances: C-C & C-H bonds are unreactive.

propane structure.gif (2915 bytes) (http://www.moorlandschool.co.uk/earth/Oil%20Refinery/propane%20structure.gif)Propane molecule

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  • Also organic molecules- but not hydrocarbons: oxygen is present.
  • The hydroxy group gives alcohols its' characteristics: -OH.
  • This is the functional group in an organic molecule.
  • Methanol is the simplest alcohol

(http://4.bp.blogspot.com/_6f-2wMOiMjA/TFMiIMY6NQI/AAAAAAAAAKI/jXJcXaRiWmQ/s1600/Methanol_structure_simple.png)Methanol structure

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Alcohols Cont.


  • After methanol comes ethanol: C2H5OH.
  • Alcohols burn in air = CO2 and H2O
  • They are combustible because of the hydrocarbon in the chain.
  • Alochol reacts with sodium less vigorously than sodium with water.
  • Sodium replaces the hydrogen in the hydroxy group of the molecule.
  • The products of the reaction are sodium ethoxide and hydrogen gas. 
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