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Topic: how do i write the structure of cyclopentenol?  (Read 4294 times)

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Offline nitelychos

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how do i write the structure of cyclopentenol?
« on: February 16, 2012, 04:22:07 PM »
according to my textbook 2-cyclopentenol and 3-cyclopentenol each have a double bond somewhere in their rings. apparently the 2 and the 3 changes the position of the double bond because that is the only difference in the two structures.
but my question is how am i susposed to know that their is a double bond in this molecule just from the name cyclopentenol alone. if asked to write the structural formula of this molecule based on the name alone, how am i suposed to do it correctly?
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Offline OrgoTutor

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Re: how do i write the structure of cyclopentenol?
« Reply #1 on: February 16, 2012, 04:37:46 PM »
Quote from: nitelychos on February 16, 2012, 04:22:07 PM
but my question is how am i susposed to know that their is a double bond in this molecule just from the name cyclopentenol alone. if asked to write the structural formula of this molecule based on the name alone, how am i suposed to do it correctly?

The second "e" in the name "cyclopentenol" tells you there is a double bond in the ring. For a five-member ring with no double bond the name would be "cyclopentanol." These follow the same naming trend as the straight-chain compounds "pentane" (all single bonds), "pentene" (one double bond), and "pentyne" (one triple bond).
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Offline nitelychos

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Re: how do i write the structure of cyclopentenol?
« Reply #2 on: February 16, 2012, 04:41:20 PM »
wow! thats so simple so it follows that same alkane, alkene, alkyne rules. i really need to find some help on the naming conventions it been a long time since i took general chemistry.
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Offline Honclbrif

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Re: how do i write the structure of cyclopentenol?
« Reply #3 on: February 16, 2012, 06:06:01 PM »
Furthermore, the double bonded carbons in a ring are always numbered 1 and 2. You need to determine where the substituents are on the ring in relation to this.
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Offline OrgoTutor

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Re: how do i write the structure of cyclopentenol?
« Reply #4 on: February 16, 2012, 06:52:45 PM »
Quote from: Honclbrif on February 16, 2012, 06:06:01 PM
Furthermore, the double bonded carbons in a ring are always numbered 1 and 2. You need to determine where the substituents are on the ring in relation to this.

Well not always. It depends on what other substituents are also on the ring and the relative priorities of those substituents. For 2-cyclopentenol, the hydroxyl group (-OH) has higher priority than the double bond--therefore, the carbon to which the -OH is attached is numbered 1, and the double bond is located between carbons numbered 2 and 3.
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Offline Honclbrif

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Re: how do i write the structure of cyclopentenol?
« Reply #5 on: February 17, 2012, 06:55:56 AM »
You're right. Looks like its been too long since I've reviewed my nomenclature.
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