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F324 January 2012 Paracetamol Benzene + Bromine help [PLEASE HELP] Watch

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    The question and corresponding answer is given.

    Why are there two bromines rather than just one?

    I'm confused why the bromine atoms are placed on either side of the benzene molecule.

    Thanks.
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    (Original post by nwmyname)
    The question and corresponding answer is given.

    Why are there two bromines rather than just one?

    I'm confused why the bromine atoms are placed on either side of the benzene molecule.

    Thanks.
    The -OH group attached to the benzene ring is 2,4,6 directing and activating. Hence the tendency would be for triple substitution, but in this case the 4- position is already taken up so substitution happens at only the 2 and 6 positions of the ring.
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    (Original post by charco)
    The -OH group attached to the benzene ring is 2,4,6 directing and activating. Hence the tendency would be for triple substitution, but in this case the 4- position is already taken up so substitution happens at only the 2 and 6 positions of the ring.
    Got you!
    Thanks.
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    (Original post by charco)
    The -OH group attached to the benzene ring is 2,4,6 directing and activating. Hence the tendency would be for triple substitution, but in this case the 4- position is already taken up so substitution happens at only the 2 and 6 positions of the ring.
    Hold on
    the Br groups are only at the 2 and the 5 positions.
    how is this the case.
    It is not 6.

    No I think because the OH is 2 and 4 activating but so is the -NHR group which also does the same job.

    The Br is in position 2 from the -OH and so the -NHR group is in 4 if seen anticlockwise (Down then up)

    Please help!
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    (Original post by nwmyname)
    Hold on
    the Br groups are only at the 2 and the 5 positions.
    how is this the case.
    It is not 6.

    No I think because the OH is 2 and 4 activating but so is the -NHR group which also does the same job.

    The Br is in position 2 from the -OH and so the -NHR group is in 4 if seen anticlockwise (Down then up)

    Please help!
    The Brs are at the 2 and 6 positions, with the -OH attached at 1. Count again.

    It's an -NHCOR group which is o/p directing but not as strongly as -OH (think of this in terms of how much electron density is donated to the π system).
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    (Original post by alow)
    The Brs are at the 2 and 6 positions, with the -OH attached at 1. Count again.

    It's an -NHCOR group which is o/p directing but not as strongly as -OH (think of this in terms of how much electron density is donated to the π system).
    Got it.
    Now it makes sense perfectly.
    Thanks very much
 
 
 
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