-ene Nomenclature (semi-structural formulas)

  • Thread starter Rudders
  • Start date
  • #1
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Hi,

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:
CH3CH2CH=CH2

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

Thanks
-Rudders
 

Answers and Replies

  • #2
alxm
Science Advisor
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9
What does that equals sign mean? Does it represent where the double bond is located?
Yes.

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