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CO20. Conjugate Addition-Elimination in Aromatics

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    4229
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    CO20. Conjugate Addition & Elimination in Aromatics

    In conjugate addition, a carbonyl group turns a neighbouring alkene into an electrophilic site. An enone, such as the one below, has two electrophilic positions.

    COconjres_2sea.png

    A similar situation happens when pi-acceptors such as nitro groups are attached to aromatic rings.

    COarsub_cj3e.png

    The key step in the mechanism is the loss of the halide ion, which allows the aromaticity to be restored.

    COarsub_ude3.png

    Problem CO20.2.

    The location of the halogen and the electron-withdrawing group matters. Explain why the reaction occurs if the groups are in the 1 and 2 positions (ortho to each other) or the 1 and 4 positions (para to each other), but not if they are in the 1 and 3 positions (meta to each other).

    COarsubomp_cctt.png

    Problem CO20.3.

    Explain why the reaction is faster if additional electron-withdrawing groups are present.

    COarsubrate_saaz.png


    This page titled CO20. Conjugate Addition-Elimination in Aromatics is shared under a CC BY-NC 3.0 license and was authored, remixed, and/or curated by Chris Schaller.

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