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2-bromo-3-chlorobutane or 3-bromo-2-chloro-butane Watch

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    I know it isn't the Blue Book, but...

    https://www.iupac.org/fileadmin/user_upload/publications/recommendations/CompleteDraft.pdf

    Page 387 assigns seniority F > Cl > Br > I

    ...and page 42 says they are written alphabetically.

    Which makes 3-bromo-2-chloro-butane correct.

    Correct?
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    (Original post by Pigster)
    I know it isn't the Blue Book, but...

    https://www.iupac.org/fileadmin/user_upload/publications/recommendations/CompleteDraft.pdf

    Page 387 assigns seniority F > Cl > Br > I

    ...and page 42 says they are written alphabetically.

    Which makes 3-bromo-2-chloro-butane correct.

    Correct?
    google thinks it's 2-bromo-3-chlorobutane
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    (Original post by Pigster)
    I know it isn't the Blue Book, but...

    https://www.iupac.org/fileadmin/user_upload/publications/recommendations/CompleteDraft.pdf

    Page 387 assigns seniority F > Cl > Br > I

    ...and page 42 says they are written alphabetically.

    Which makes 3-bromo-2-chloro-butane correct.

    Correct?
    the substituent groups are almost always written alphabetically, so yes, 3-bromo-2-chloro-butane is correct
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    (Original post by MexicanKeith)
    google thinks it's 2-bromo-3-chlorobutane
    We were told do them in numerical order too. e.g. 2-methyl,3-ethylpentane
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    Yup I believe the seniority determines the locant number. Higher seniority = assign lower locant. So since chlorine has higher seniority than bromine it is on second carbon and bromine is on third carbon. In nomenclature when writing prefix we use alphabetical order.

    Hence 3-bromo-2-chlorobutane is correct. The numbers are assigned by seniority and the order in which they are written is alphabetical
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    (Original post by CTLevers)
    We were told do them in numerical order too. e.g. 2-methyl,3-ethylpentane
    -ethyl and -methyl have no seniority over each other, so should be written alphabetically and then their numbering is then based on their position in the alphabet. 3-ethyl-2-methylpentane is what you should have put.

    Whereas halogens show seniority to each other, which overrules alphabetics in assigning their locant position, but not their order when written.
 
 
 
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