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Homework Help: Melting Points trend for Primary Alcohols

  1. Mar 1, 2008 #1
    1. What is the trend of melting points for primary alcohols?

    I can't understand why melting points dramatically change such as the increase is molecular weight. The melting points doesn't increase nor decrease but they increase and decrease differently when you increase the molecular weight.

    Thanks
     
  2. jcsd
  3. Mar 2, 2008 #2
    this may be because of branching..... organic molecules do not necessarily exist as straight chain molecules but have different isomers. the more branched the isomers are, the lesser are the points of contact between them. van der waal forces of attraction decreases and melting point also decreases. straight chain isomers have more points of contacts between them, they have a higher melting point.



    or some isomers (optical) might be polar and others non polar. you have cis but 2 ene and trans but 2 ene. cis but 2 ene is polar and has a higher melting point.

    it does not only occur in alcohols but in many other families of organic molecules...
     
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