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why does 2,4,6- tribromobenzene form instead of 1,3,5- tribromobenzene? Watch

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    http://i.imgur.com/POqJrZ0h.jpg in the post you can see it's mentioned "The OH group "activates" the benzene ring by increasing the electron density - especially at carbons 2, 4 and 6".. My deduction of the above statement is that the oxygen's electron density is pulled to the nearest 3 carbons - Carbon no. 6, 1 and 2. Due to electron - electron repulsion, the electron density of carbon - 5 and carbon -3 in phenol are shifted to carbon 6. Thus carbons 2, 4,6 and 1 have most electron density. Leaving the carbon 1 which is attached to the oxygen, the bromine atoms attack carbon 2, 4 and 6 since they are rich in electrons. Is my deduction correct? Someone please clear my doubts. One more question...which maybe off topic - why is the OH group in phenol not substituted by bromine since carbon 1 is also rich in electrons?






    Edit: the title should be : why does 2,4,6- tribromophenol form instead of 1,3,5- tribromophenol?
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    (Original post by thebrahmabull)
    http://i.imgur.com/POqJrZ0h.jpg in the post you can see it's mentioned "The OH group "activates" the benzene ring by increasing the electron density - especially at carbons 2, 4 and 6".. My deduction of the above statement is that the oxygen's electron density is pulled to the nearest 3 carbons - Carbon no. 6, 1 and 2. Due to electron - electron repulsion, the electron density of carbon - 5 and carbon -3 in phenol are shifted to carbon 6. Thus carbons 2, 4,6 and 1 have most electron density. Leaving the carbon 1 which is attached to the oxygen, the bromine atoms attack carbon 2, 4 and 6 since they are rich in electrons. Is my deduction correct? Someone please clear my doubts. One more question...which maybe off topic - why is the OH group in phenol not substituted by bromine since carbon 1 is also rich in electrons?






    Edit: the title should be : why does 2,4,6- tribromophenol form instead of 1,3,5- tribromophenol?

    Directing effect of substituents on a benzene ring are divided into four kinds:

    +M, -M, +I, -I

    The hydroxyl group is +M, i.e. that it exerts a positive mesomeric effect, meaning that it has a lone pair of electrons that can conjugate into the ring to either stabilise the intermediates formed in the electrophilic substitution mechanism or to introduce extra electron density at certain carbons.

    The only way to see this is to draw out the resonance forms possible in all of the intermediates.

    Check this out - directing effects of substituents
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    which part of chemistry is this?
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    (Original post by thebrahmabull)
    http://i.imgur.com/POqJrZ0h.jpg in the post you can see it's mentioned "The OH group "activates" the benzene ring by increasing the electron density - especially at carbons 2, 4 and 6".. My deduction of the above statement is that the oxygen's electron density is pulled to the nearest 3 carbons - Carbon no. 6, 1 and 2. Due to electron - electron repulsion, the electron density of carbon - 5 and carbon -3 in phenol are shifted to carbon 6. Thus carbons 2, 4,6 and 1 have most electron density. Leaving the carbon 1 which is attached to the oxygen, the bromine atoms attack carbon 2, 4 and 6 since they are rich in electrons. Is my deduction correct? Someone please clear my doubts. One more question...which maybe off topic - why is the OH group in phenol not substituted by bromine since carbon 1 is also rich in electrons?


    Edit: the title should be : why does 2,4,6- tribromophenol form instead of 1,3,5- tribromophenol?
    Electron donating groups such as OH tend to be para and ortho directing. OH cannot be substituted by Br because it is not a strong enough nucleophile
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    (Original post by runningcat)
    which part of chemistry is this?
    Reactivity of aromatics.
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    (Original post by langlitz)
    Electron donating groups such as OH tend to be para and ortho directing. OH cannot be substituted by Br because it is not a strong enough nucleophile
    Your post makes it sound like even if Br was a strong enough nucleophile then it would displace OH which would still be wrong...
 
 
 
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