My textbook states that members of a homologous series have the same general formula (ex. $\ce{C_{n}H_{2n}}$ for alkenes) as they only differ from one to another by additional $\ce{CH_2}$ (methylene) groups. However, alkenes can have more than 1 carbon-carbon double bond, which should alter their general formula right?

  • $\begingroup$ Luke here for good definition and description. $\endgroup$ – Mathew Mahindaratne Jan 19 at 6:43
  • $\begingroup$ @MathewMahindaratne Are you suggesting that members of a homologous series need not have the general formula, only the same functional group? $\endgroup$ – David Lu Jan 19 at 6:56
  • $\begingroup$ Read carefully and look at examples given. $\endgroup$ – Mathew Mahindaratne Jan 19 at 7:12
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    $\begingroup$ There is the series for dienes and whatever number of double bounds you may wish to count and classify. Also , if the number of double bounds gets higher, usually trends and comparison is interesting with respect of the latter different n. This leads to a series, in a way, except that is of analogous rather than homologous - oligo- and polyenes. $\endgroup$ – Alchimista Jan 19 at 7:24
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    $\begingroup$ If a molecule has more than one double bond C=C, it is not an alkene. It is an alkadiene, or an alkapolyene. $\endgroup$ – Maurice Jan 19 at 15:55

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