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Size:  496.1 KBMy teacher said that this compoun is called 3-methlylbutan-2-ol but shouldn't it be called 2-methybutan2-ol because if you go the other way its 2.
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    Your teacher is right. 3-methylbutan-2-ol (or 3-methyl-2-butanol). Each carbon must have a unique number.

    Your way would be 2-methylbutan-3-ol. The alcohol group takes precedence over alkyl groups.

    Checked with ChemDoodle:
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    No, you count from one end or the other. It could be called 2-methylbutan-3-ol or 3-methylbutan-2-ol, but not 2-methylbutan-2-ol
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    (Original post by alow)
    The alcohol group takes precedence over alkyl groups
    Why is this? I dont honestly know and this will come in handy for exams
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    (Original post by an_atheist)
    No, you count from one end or the other. It could be called 2-methylbutan-3-ol or 3-methylbutan-2-ol, but not 2-methylbutan-2-ol
    No it can't. 3-methylbutan-2-ol is the correct answer.

    (Original post by an_atheist)
    Why is this? I dont honestly know and this will come in handy for exams
    Because IUPAC says so.

    More here: http://www.masterorganicchemistry.co...-nomenclature/
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    No, 2-methylbutan-2-ol would imply that the methyl group and the alcohol group are on the same carbon and unless my eyes are lying to me (which may well be the case with these oversized wrong way round images) this is not the case.
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    (Original post by alow)
    No it can't. 3-methylbutan-2-ol is the correct answer.



    Because IUPAC says so.
    Why do they say so? Surely there is some sort of criteria for this sort of thing?
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    (Original post by an_atheist)
    Why do they say so? Surely there is some sort of criteria for this sort of thing?
    Because everyone agreed to use their rules on naming compounds.

    I edited my last post to include a link. It's loosely based around the oxidation state, where more oxidised groups tend to be higher priority but that's tenuous at best. You'll have to either look it up or memorise the chart if you want to.
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    (Original post by alow)
    Because everyone agreed to use their rules on naming compounds.

    I edited my last post to include a link. It's loosely based around the oxidation state, where more oxidised groups tend to be higher priority but that's tenuous at best. You'll have to either look it up or memorise the chart if you want to.
    Cool, thanks
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    (Original post by Ann_Onymous)
    Name:  image.jpg
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Size:  496.1 KBMy teacher said that this compoun is called 3-methlylbutan-2-ol but shouldn't it be called 2-methybutan2-ol because if you go the other way its 2.
    Attachment 578500578502578600

    Your teacher is correct. According to the IUPAC rules, the numbering starts from the position which is nearest to the functional group(in this case the O-H group) is present so it cannot be 2-methylbutan-2-ol because this indicates that both the methyl group and the O-H group are on the same carbon and that is not possible according to the picture that is given. It is 3-methylbutan-2-ol.
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    (Original post by sabahshahed294)
    Your teacher is correct. According to the IUPAC rules, the numbering starts from the position which is nearest to the functional group(in this case the O-H group) is present so it cannot be 2-methylbutan-2-ol because this indicates that both the methyl group and the O-H group are on the same carbon and that is not possible according to the picture that is given. It is 3-methylbutan-2-ol.
    Oh I didn't know about that rule thats why. Thank you
 
 
 
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