## Explanation of Organic Chemistry terms.

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### Explanation of Organic Chemistry terms.

A homologous series is a family of organic compound which follows a regular structrura patterng, in which each successive member differs in its molecular formula by a $-CH_2-$.
My question is, what do the $-$ before and after $CH_2$ mean?
Last edited by chikis on July 18th, 2014, 5:34 am, edited 1 time in total.
chikis
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### Re: Explanation of Organic Chemistry terms.

chikis,

-CH2- is a methylene bridge. The two lines on either end symbolize bonds, though what's at the end of those bonds is left unspecified. If we used a more algebra-like notation, -CH2- could be written as $X$-CH2-$Y$. A simple example of something with a methlyene bridge would be propane (CH3-CH2-CH3).

The quoted text in the OP refers to something like the series of simple, linear alkanes:
1. CH4 (methane)
2. CH3-CH3 (ethane)
3. CH3-CH2-CH3 (propane)
4. CH3-CH2-CH2-CH3 (butane)
5. CH3-CH2-CH2-CH2-CH3 (pentane)
6. CH3-CH2-CH2-CH2-CH2-CH3 (hexane)
7. CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH3 (heptane)
8. etc.
The pattern being that they're all the same thing, except varying by the number of methylene bridges. Even methane's just H-CH2-H.
Natural ChemE
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### Re: Explanation of Organic Chemistry terms.

CH2 Methylene is the simplest of organic compounds which contain carbon double bonds.
redwhitechem
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### Re: Explanation of Organic Chemistry terms.

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peterle
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### Re: Explanation of Organic Chemistry terms.

peterle please don’t spam our forums :]

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