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16.E: Chemistry of Benzene: Electrophilic Aromatic Substitution (Exercises)

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    61721
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    These are the homework exercises to accompany the Textmap for McMurry's Organic Chemistry textbook.

    16.2 Other Aromatic Substitutions

    16.2 Exercises

    Questions

    Q16.2.1

    In each case, how many products would be expected for the bromination of p-xylene, o-xylene, and m-xylene?

    Q16.2.2

    If toluene is treated with D2SO4 all the hydrogen’s are replaced with deuterium. Explain. (might need to draw mechanism)

    Solutions

    S16.2.1

    S16.2.2

    The deuterium is added to the ring. When the ring “re-aromatizes” the base scavenges the hydrogen before the deuterium and therefore is left on the ring. Continues for the rest of the hydrogen on the ring.

     

    16.3 Alkylation and Acylation of Aromatic Rings: The Friedel-Crafts Reaction

    16.3 Exercises

    Questions

    Q16.3.1

    Which of the following will NOT undergo a rearrangement in a Friedel-Crafts reaction?

    Q16.3.2

    Suggest an acyl chloride that was used to make the following compounds:

    Solutions

    S16.3.1

    A and E will not undergo a rearrangement.

    S16.3.2

    16.4 Substituent Effects in Substituted Aromatic Rings

    16.4 Exercises

    Questions

    Q16.4.1

    Draw the resonance structures for benzaldehyde to show the electron-withdrawing group.

    Q16.4.2

    Draw the resonance structures for methoxybenzene to show the electron-donating group.

    Solutions

    S16.4.1

    S16.4.2

    16.5 An Explanation of Substituent Effects

    16.5 Exercises

    Questions

    Q16.5.1

    (Trichlorometyl)benzene has a strong concentration of electrons at the methyl substituent. Comparing this toluene, which is more reactive toward electrophilic substitution?

    Q16.5.2

    The following compound is less reactive towards electrophilic substitution than aniline? Explain.

    Q16.5.3

    Consider the intermediates of the following molecule during an electrophilic substitution. Draw resonance structures for ortho, meta, and para attacks.

    Solutions

    S16.5.1

    The trichloromethyl group is an electron donor into the benzene ring, therefore making it more stable and therefore more reactive compared to electrophilic substitution.

    S16.5.2

    As seen in resonance the electron density is also localized off of the ring, thereby deactivating it compared to aniline.

    S16.5.3

    16.6 Trisubstituted Benzenes: Additivity of Effects

    16.6 Exercises

    Questions

    Q16.6.1

    Predict the products of the following reactions:

    Solutions

    S16.6.1

    16.7 Nucleophilic Aromatic Substitution

    16.7 Exercises

    Questions

    Q16.7.1

    Propose a mechanism for the following reaction:

    Solutions

    S16.7.1

    16.8 Benzyne

    16.8 Exercises

    Questions

    Q16.8.1

    When p-chlorotoluene is reacted with NaOH, two products are seen. While when m-chlorotoluene is reacted with NaOH, three products are seen. Explain this.

    Solutions

    S16.8.1

    You need to look at the benzyne intermediates. The para substituted only allows for two products, while the para produces two different alkynes which give three different products.

    16.9 Oxidation of Aromatic Compounds

    16.9 Exercises

    Questions

    Q16.9.1

    Predict the products.

    Q16.9.2

    Consider a benzyl radical. Would it be more stable than an alkyl radical? Explain.

    Q16.9.3

    How would you make the following molecule?

    Solutions

    S16.9.1

    The second one leads to no reaction because it requires a hydrogen just off the phenyl ring.

    S16.9.2

    Yes it would be more stable than an alkyl radical, consider the pi system able to stabilize through resonance.

    S16.9.3

    The following is just one possibility.

    16.10 Reduction of Aromatic Compounds

    16.10 Exercises

    Questions

    Q16.10.1

    How would you make the following from benzene and an acid chloride?

    Solutions

    S16.10.1

    16.11 Synthesis of Polysubstituted Benzenes

    16.11 Exercises

    Questions

    Q16.11.1

    How would make the following compounds from benzene?

    A) m-bromonitrobenzene

    B) m-bromoethylbenzene

    Q16.11.2

    There is something wrong with the following reaction, what is it?

    Solutions

    S16.11.1

    This is just one possible way to synthesize it.

    S16.11.2

    The bromine should be in the meta position. Right now it is in the ortho position, from perhaps having the ethyl group present first and then the having it substituted there. BUT the ethyl group is last to form, and the aldehyde and nitro groups would both encourage a meta substitution.

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