F322: Basic Hydrocarbon Concepts

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Introduction

  • A hydrocarbon is a molecule that contains only H, C and O.
  • Saturated means that there are only single bonds.
  • Unsaturated means that there are double bonds, i.e. C=C.
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Formulae

  • Empirical = The simplest whole number ratio of atoms of each element in a compound.
    E.g. CH2 or C2H5
  • Molecular = The actual number of atoms of each element in a compound.
    E.g. C4H8 or C4H10
  • Structural = The minimal detail to show the arrangement of atoms.
    E.g. CH3CH2CH2CH3
  • Displayed = Shows all atoms and bonds.
    E.g. 
  • Skeletal = Shows the structure.
    E.g.  
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Naming

-Homologous series is molecules possessing the same functional group where each member of the series differs by a -CH2.
-Functional Group is an atom or group of atoms that give the molecule the chemical properties.

Rules: 

  • Name the longest carbon chain.
  • Identify the functional groups and alkyl groups.
  • Assign numbers to the functional groups and alkyl groups choosing numbers that are as small as possible.
  • Use di, tri, tetra, to indicate how many functional groups there are.
  • If there is more than one alkyl group place the names alphabetically.
  • If COOH present this is carbon-1.
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Homologous Series

  • Alkane: E.g. Propane 
  • Alkene: C=C functional group, E.g. Propene.
  • Amine: -NH2, E.g. Propyl amine.
  • Haloalkane:-F/Cl/Br, E.g. 1-chloropropane.
  • Aldehyde: -CHO, E.g. Propanal.
  • Alcohol: -O-H, E.g. Propanol.
  • Ketone: -COC, E.g. Propanone.
  • Carboxylic Acid: -COOH, E.g. Propanoic Acid.
  • Ester: -OCO, E.g. Methyl Ethanoate.  
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Isomerism

  • Structural Isomerism - Molecules with the same molecular formula but with different structural arrangement of atoms.
    E.g. C4H10
      
  • Sterioisomers - Compounds with the same structural formula, but different arrangement of atoms in space.
  • E/Z is a special kind that requires a C=C bond to restrict rotation, and both of these must be attatched to a different group.
     
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Bond Fission

  • Homolytic - Breaking of the covalent bond where one of the bonded electrons goes to each atom, forming two radicals. Cl-Cl -> Cl. + Cl. (Radical = Species with an unpaired electron).
  • Heterolytic - Breaking of the covalent bond where both of the bonded electrons going to one of the atoms to form a cation and an anion. H-Cl -> H+ + Cl-
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Atom Economy & Percentage Yield

  • Atom Economy - The efficiency of a reaction, looking at all the atoms involved.
    Atom Economy = (Mr of desired product / sum of Mr of all products) x 100 
    Subsitution and Elimination reactions are LESS efficient compared with Addition.
  • Percentage Yield - The efficiency of converting reactants to product. 
    Percentage Yield = (Actual mass / Predicted [Theoretical] mass) x 100 
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