Benzene & Aromaticity Quiz
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Benzene & Aromaticity Quiz

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Questions and Answers

What is the empirical formula of benzene?

  • C6H6 (correct)
  • C6H10
  • C7H6
  • C5H5

    • Kekulé's structure of benzene accurately predicts its reactivity with reactions involving Br2.

    False

    Who isolated benzene, and in what year?

    Michael Faraday, 1825

    The unique stability of benzene is partly attributed to its __________ structures.

    <p>resonance</p> Signup and view all the answers

    Match the following scientists with their proposals regarding benzene:

    <p>Michael Faraday = Isolated benzene in 1825 Kekulé = Proposed alternating single and double bonds Claus = Suggested an incorrect structure for benzene Dewar = Another structure proposal in 1867</p> Signup and view all the answers

    What is Hückel's rule related to?

    <p>Identifying aromatic compounds</p> Signup and view all the answers

    Resonance leads to a decrease in the stability of aromatic compounds.

    <p>False</p> Signup and view all the answers

    What is the significance of the experimental heat of hydrogenation of benzene?

    <p>It shows that benzene is more stable than predicted for a simple triene.</p> Signup and view all the answers

    Which of the following is a requirement for a compound to be classified as aromatic according to Hückel's rules?

    <p>It must be a planar ring system with conjugated p electrons.</p> Signup and view all the answers

    Aroma compounds must have unshared pairs of electrons involved in aromaticity.

    <p>False</p> Signup and view all the answers

    What is the formula to determine the number of p electrons in aromatic compounds?

    <p>(4n + 2)</p> Signup and view all the answers

    Benzene is stabilized by a cloud of __ in a delocalized p-system.

    <p>electrons</p> Signup and view all the answers

    Match the following compounds with their respective characteristics:

    <p>Benzene = Stable due to delocalized p electrons Phenol = A hydroxyl group attached to an aromatic ring Pyridine = A heteroaromatic compound with a nitrogen atom Aniline = An amine group attached to an aromatic ring</p> Signup and view all the answers

    Which of the following statements about hetero-aromatic compounds is true?

    <p>They can contain non-carbon atoms in the aromatic ring.</p> Signup and view all the answers

    Benzene has a resonance structure that is a significant factor in its stability.

    <p>True</p> Signup and view all the answers

    What type of hybridization do the carbon atoms in benzene typically exhibit?

    <p>sp2</p> Signup and view all the answers

    Which of the following statements about phenols is correct?

    <p>Phenol is more acidic than ethanol.</p> Signup and view all the answers

    The resonance stabilization of the phenoxide anion involves spreading the negative charge around.

    <p>True</p> Signup and view all the answers

    What is the $pK_a$ value of phenol?

    <p>9.99</p> Signup and view all the answers

    The antibacterial compound used in acne treatment is called ______.

    <p>resorcinol</p> Signup and view all the answers

    Match the following compounds with their corresponding pK_a values:

    <p>Phenol = 9.99 Acetic Acid = 15.9 Resorcinol = Not Given Ethanol = Not Given</p> Signup and view all the answers

    What type of model is used to understand the structure and reactivity of molecules when a single Lewis structure is insufficient?

    <p>Resonance theory</p> Signup and view all the answers

    Capsaicin is primarily used in treating acne.

    <p>False</p> Signup and view all the answers

    What is the mechanism by which the phenoxide anion is stabilized?

    <p>Resonance</p> Signup and view all the answers

    What is the value of Kb for the reaction involving NH2?

    <p>4.5 × 10^-4</p> Signup and view all the answers

    The pKb value of aniline is 9.36.

    <p>False</p> Signup and view all the answers

    What do resonance structures help predict in aniline?

    <p>Reactivity</p> Signup and view all the answers

    The basicity of aniline is associated with a Kb value of _____ × 10^-4.

    <p>4.5</p> Signup and view all the answers

    Match the following terms with their respective values:

    <p>Kb for NH2 = 4.5 × 10^-10 Kb for aniline = 4.5 × 10^-4 pKb of aniline = 3.34 pKb of NH2 = 9.36</p> Signup and view all the answers

    Which of the following correctly defines resonance structures?

    <p>Different representations of a molecule that help explain its reactivity.</p> Signup and view all the answers

    Resonance structures are actual structures that exist independently.

    <p>False</p> Signup and view all the answers

    What is the primary function of resonance structures in chemistry?

    <p>To explain reactivity and stability of molecules.</p> Signup and view all the answers

    Aniline is a type of _______ that is commonly used in the dyeing industry.

    <p>amine</p> Signup and view all the answers

    Which of the following is true regarding the basicity of aniline?

    <p>Aniline is approximately 106 times less basic than cyclohexylamine.</p> Signup and view all the answers

    Match the following components with their properties or functions:

    <p>Aniline = Weak base used in dye industry Resonance arrow = Indicates resonance structures BASF = Largest chemical manufacturing company Cyclohexylamine = Stronger base than aniline</p> Signup and view all the answers

    What is the significance of lone pairs on atoms in resonance structures?

    <p>They allow for the formation of multiple resonance structures.</p> Signup and view all the answers

    The actual structure of a molecule can be represented as a single resonance structure.

    <p>False</p> Signup and view all the answers

    The largest chemical manufacturing company in the world is _______.

    <p>BASF</p> Signup and view all the answers

    Study Notes

    Benzene & Aromaticity

    • Benzene is a stable molecule with the formula C6H6.
    • Michael Faraday isolated Benzene in 1825 from the residue of illuminating gas.
    • Benzene was initially proposed to have alternating single and double bonds (Kekulé's Model, 1865).
    • This model did not accurately predict the stability of benzene as determined by hydrogenation studies.
    • Hückel's Rules were developed to determine if a molecule is aromatic.
      • The molecule must be a planar ring system with conjugated π-electrons
      • The number of π-electrons must be equal to (4n + 2), where n is an integer.
        • For example, benzene has 6 π-electrons (4 * 1 + 2 = 6)
    • Molecules that meet Hückel's Rules are considered aromatic.
    • Benzene's stability comes from electron delocalization in a cloud of electrons in a delocalized p-system.

    Heterocyclic Aromatics

    • Aromatic compounds can include heterocycles, which contain atoms other than carbon in the ring.
    • Some common examples include:
      • Pyridine (C5H5N)
      • Furan (C4H4O)
      • Pyrrole (C4H4NH)
      • These molecules are aromatic because they meet Hückel's Rules.

    Phenol

    • Phenol is a commonly occurring compound with the formula C6H5OH.
    • Phenol is a stronger acid than ethanol due to the resonance stabilization of the phenoxide anion.
    • The negative charge in the phenoxide anion is delocalized over the benzene ring, making it more stable.

    Resonance Structures

    • Resonance structures are used to explain the structure and reactivity of molecules where a single Lewis structure is insufficient.
    • They are hypothetical structures that contribute to the actual structure of the molecule (the resonance hybrid).
    • The resonance hybrid is a weighted average of the contributing resonance structures.

    Aniline

    • Aniline (C6H5NH2) is a common compound used in the dyeing industry.
    • Aniline is a weaker base than cyclohexylamine due to the resonance delocalization of the lone pair on the nitrogen atom.
    • The lone pair on the nitrogen atom is delocalized into the benzene ring, making it less available for protonation.

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    Week 2 Online Lecture Slides: Hydrocarbons, Aromaticity, Phenols & Anilines - PDF

    Description

    Test your knowledge on Benzene and its properties along with the concept of aromaticity. This quiz covers key historical developments, models, and Hückel's Rules that define aromatic compounds. Understand the stability of Benzene and the role of heterocyclic aromatics in chemistry.

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