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-ene Nomenclature (semi-structural formulas)

  1. May 14, 2009 #1

    I was just confused as to the semi-structural formula nomenclature of -ene and -yne structures. The thing that I don't understand is the = sign in the formula.

    For example:

    What does that equals sign mean? Does it represent where the double bond is located?

    If so, why does ethene have the structural formula CH2CH2 instead of CH2=CH2

  2. jcsd
  3. May 14, 2009 #2


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    Science Advisor


    You can write it both ways. CH2CH2 is the 'normal' way, whereas when you use an equal sign to represent the double bond you're approximating the structure diagram in text. Formally you should really stick to either the formula or a full and proper structure diagram, but in informal contexts it can be useful.
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