Alkenes and Alcohols

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E/Z isomerism

  • Same molecular formula but different structurl formula.
  • Restricted roatation around planar double bond.
  • Stereoisomers = same molecular and structural formula, but different three-dimensional arrangment in space. 
  • Z = On the same side.
  • E = On the oppisite side.
  • Groups are ranked using CIP priority, atomic number used for this. 
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Addition polymers

  • Polymers are named from the alkenes in which they were formed from e.g (poly(ethene), poly(pentene)).
  • Addition polymers are unreactive and so are used widespread as inert materials.
  • High density poly(ethene) is used for kitchen ware and low density poly(ethene) is used for plastic bags.  
  • Strong covalent bonds within polymers and weak van der waals between polymers.
  • Having fewer branches = stronger VDW forces, stronger and harder material
  • More branches = weaker VDW forces, weaker and softer materials.
  • Longer the chain = stonger VDW forces/higher melting point.  
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Reactions of Alkenes

  • C=C bond = high electron density, so susceptable to electrophiles.
  • Electrophiles = a substance which can accept a pair of electrons, polar molecules.
  • Addition reaction = two molecules join together to make one larger moleculeImage result for electrophilic addition mechanism (http://alevelchem.com/img/electrophilic_addition_bromine.gif)
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Production of ethanol from ethene

  • Hydration = adding water to a substance.
  • Catalyst = concentrated phosphuric acid.
  • Mixture is kept at 60atm and 600K to ensure 100% yield. Side reactions can reduce the yield.Image result for production of ethanol from ethene and steam
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Physical properties of alcohols

  • Greater boiling point than alkenes, similar relative molecular mass due to the presence of hydrogen bonding between molecules.
  • Short chain alcohols are soluble in water, alkanes are not. 
  • Primary alcohols = 1 R group, Secondary = 2 R groups, Tertiary = 3 R groups.

Image result for classification of alcohols primary secondary tertiary (http://study.com/cimages/multimages/16/alcohol_classify.png)

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Reactions of Alcohols

Oxidation:

  • Primary alcohols are easily oxidised to produce aldehydes. Secondary oxidised to produce ketones and Tertiary = not easily oxidised. 

Elimination:

  • Where one small molecule is removed from a reactant molecule.
  • A molecule of water can be removed to produce an alkene. 
  • Can also be described as a dehydration reaction, where a molecule of water is eliminated. 

Image result for dehydration reaction apparatus (http://www.rsc.org/learn-chemistry/Content/FileRepository/frg/images//Dehydration%20of%20ethanol%20to%20form%20ethene%201.JPG)

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Production of ethanol

Fermentation:

  • When yeast and bacteria turn sugars into alcohols.
  • Turns glucose into ethanol and CO2.

Hydration of ethene: 

  • Ethene + steam <--> ethanol. 
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