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7.6: Solutions to Selected Problems

  • Page ID
    189879
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    Exercise 7.1.1:

    ARsimplesoln.png

    Exercise 7.2.1:

    In the case of uncatalyzed bromination reactions, there is clear evidence that the Br-Br bond-breaking step does not start the reaction off. If that were the first step, there would presumably be an equilibrium between Br2 and Br+/Br- ions. That equilibrium would be shifted back toward Br2 if bromide salts were added. In that case, the amount of bromine cation would be suppressed and the reaction would slow down. No such salt effects are observed, however. That evidence suggests that, in the uncatalyzed reaction, the aromatic reacts directly with Br2.

    Exercise 7.2.2:

    In each case, a base must remove the proton from the cationic intermediate. An anion that would be present in solution has been chosen for this role.

    a)

    ARnitrationmech.png

    Exercise 7.3.2:

    ARalkylformn.png

    Exercise 7.3.3:

    The primary cation formed is very unstable. As a result, there is a high barrier to cation formation.

    ARprimalkylformn.png

    Exercise 7.3.4:

    ARalkylshiftformn.png

    Exercise 7.3.5:

    ARacylformn.png

    Exercise 7.3.6:

    ARacylcat.png

    The cation that results is stabilized via π-donation from oxygen.

    Exercise 7.3.7:

    ARnitroformn.png

    Exercise 7.3.8:

    ARso3formn.png

    Exercise 7.4.2:

    ARphenoldonor.png

    Exercise 7.4.3:

    AResteracceptor.png

    Exercise 7.4.4:

    ARtolcation.png

    Exercise 7.4.5:

    This is a substituted alkyl group. An alkyl group should be moderately activating, but the presence of a halogen exerts an inductive electron-withdrawing effect. The cation-stabilizing effect of the alkyl substituent is completely counteracted by the halogen.

    Exercise 7.4.6:

    a) activating b) deactivating c) activating d) deactivating e) deactivating

    Exercise 7.5.1:

    ARtolortho.png

    The tertiary cations that result during ortho- and meta- substitution offer extra stability, leading to preferential formation of these cations.

    Exercise 7.5.2:

    ARClmeta.png

    The π-donation that occurs in the cations arising from ortho- and meta- substitution results in extra stability, leading to preferential formation of these cations.

    Exercise 7.5.3:

    ARketmeta.png
    ARketpara.png
    ARketortho.png

    The cation directly adjacent to the carbonyl is destabilized by the electron withdrawing effect of the ketone. By default, the other intermediate is preferentially formed.

    Exercise 7.5.4:

    ARacNHpara.png
    ARacNHortho.png
    ARacNHmeta.png

    The π-donation that occurs in the cations arising from ortho- and meta- substitution results in extra stability, leading to preferential formation of these cations.

    Exercise 7.5.5:

    ARompsoln.png

    Exercise 7.5.6:

    ARsynthsoln.png

    Exercise 7.5.7:

    In cases leading to mixtures of ortho and para products, only one product was chosen, based on minimal steric interactions.

    ARdirectorwinsoln.png

    Exercise 7.5.8:

    R2 Synthesis prob solutions.png

    Exercise 7.5.9:

    ARsubsynthsoln.png

    Exercise 7.5.10:

    ARsubsynthsoln2.png

    Exercise 7.5.11:

    LaetevirenolAnswer.png

    Exercise 7.5.12:

    CheryllineAnswer.png

    This page titled 7.6: Solutions to Selected Problems is shared under a CC BY-NC 3.0 license and was authored, remixed, and/or curated by Chris Schaller via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.

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