The Unusual Reactivity and Stability of Benzene
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Questions and Answers

Which of the following is a characteristic of aromatic compounds?

  • They are not cyclic
  • They have a low heat of hydrogenation (correct)
  • They undergo addition reactions typical of other highly unsaturated compounds
  • They do not contain p orbitals

    • According to Hückel's rule, how many π electrons are required for a compound to be aromatic?

  • 2
  • 4
  • 6 (correct)
  • 8

    • Which of the following compounds is antiaromatic?

  • Cyclooctatetraene
  • Cyclobutadiene (correct)
  • Cyclopentadiene
  • Benzene

    • Which of the following compounds satisfies all the criteria for aromaticity?

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

    Which of the following compounds is not aromatic?

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

    How many π electrons are required for a completely conjugated, planar, 8-membered ring to be aromatic?

    <p>14</p> Signup and view all the answers

    Which of the following compounds is NOT considered aromatic?

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

    How many pi electrons are present in the pyrimidine-derived DNA base cytosine?

    <p>6</p> Signup and view all the answers

    Which of the following statements about molecular orbital (MO) theory is correct?

    <p>MO theory explains bonding in aromatic compounds.</p> Signup and view all the answers

    What is the basis of Hückel's rule?

    <p>The number of electrons in the compound.</p> Signup and view all the answers

    Which of the following compounds is considered fully conjugated and aromatic?

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

    In pyridine, where is the nonbonded electron pair localized?

    <p>On the nitrogen atom</p> Signup and view all the answers

    Which of the following statements about benzene is true?

    <p>Benzene has four degrees of unsaturation.</p> Signup and view all the answers

    What is the result of benzene reacting with bromine in the presence of a Lewis acid?

    <p>Substitution reaction</p> Signup and view all the answers

    What did August Kekulé propose about the structure of benzene?

    <p>Benzene contains a six-membered ring with alternating single and double bonds.</p> Signup and view all the answers

    What is the basis for current descriptions of benzene?

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

    What must any structure for benzene account for?

    <p>It contains a six-membered ring and three additional degrees of unsaturation.</p> Signup and view all the answers

    True or False: Benzene is a highly reactive hydrocarbon.

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

    Which of the following best describes the bond lengths in benzene?

    <p>Benzene has three short double bonds alternating with three longer single bonds</p> Signup and view all the answers

    Which of the following statements about the resonance description of benzene is true?

    <p>The true structure of benzene is a hybrid of two Lewis structures</p> Signup and view all the answers

    Which of the following correctly describes the number of π electrons in benzene?

    <p>Benzene has six π electrons</p> Signup and view all the answers

    Which of the following statements about the actual bond length in benzene is true?

    <p>The actual bond length in benzene is shorter than the carbon–carbon single bond</p> Signup and view all the answers

    Which of the following statements about the electron density in benzene is true?

    <p>The electron density in benzene is evenly distributed throughout the molecule</p> Signup and view all the answers

    Which of the following statements about naming substituted benzenes is true?

    <p>To name a benzene ring with one substituent, you need to name the substituent and add the word benzene</p> Signup and view all the answers

    Which statement best describes the molecular orbitals of benzene?

    <p>There are 6 pi molecular orbitals formed by the combination of 6 atomic p orbitals.</p> Signup and view all the answers

    Which of the following is NOT a characteristic of the molecular orbitals of benzene?

    <p>The larger the number of nodes, the higher in energy the MO.</p> Signup and view all the answers

    What is the inscribed polygon method used for?

    <p>Determining the aromaticity of monocyclic completely conjugated systems.</p> Signup and view all the answers

    What is the relationship between the number of MOs and the number of vertices in the inscribed polygon method?

    <p>The number of MOs is always equal to the number of vertices of the polygon.</p> Signup and view all the answers

    Which statement best describes pi stacking?

    <p>All of the above</p> Signup and view all the answers

    What is the purpose of the inscribed polygon method in predicting aromaticity?

    <p>To determine the aromaticity of a monocyclic completely conjugated system.</p> Signup and view all the answers

    According to the text, what is the basis for the current description of benzene?

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

    What did August Kekulé propose about the structure of benzene?

    <p>It is a rapidly equilibrating mixture of two compounds with alternating bonds</p> Signup and view all the answers

    Which of the following compounds is considered fully conjugated and aromatic?

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

    According to Hückel's rule, how many π electrons are required for a compound to be aromatic?

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

    Which of the following compounds satisfies all the criteria for aromaticity?

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

    What is the result of benzene reacting with bromine in the presence of a Lewis acid?

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

    Which of the following is true about the bond lengths in benzene?

    <p>All bond lengths are equal</p> Signup and view all the answers

    What is the true structure of benzene?

    <p>A resonance hybrid of two equivalent Lewis structures</p> Signup and view all the answers

    How many π electrons does benzene have?

    <p>6</p> Signup and view all the answers

    What is the actual bond length in benzene?

    <p>Intermediate between a carbon-carbon single bond and a carbon-carbon double bond</p> Signup and view all the answers

    How many atoms surround each carbon atom in a benzene ring?

    <p>3</p> Signup and view all the answers

    What is a benzene substituent called?

    <p>Phenyl group</p> Signup and view all the answers

    Which of the following is true about the molecular orbitals of benzene?

    <p>There are six pi molecular orbitals</p> Signup and view all the answers

    What is the lowest energy bonding molecular orbital in benzene?

    <p>Ψ1</p> Signup and view all the answers

    Which of the following statements about the inscribed polygon method is true?

    <p>It works for all monocyclic completely conjugated systems</p> Signup and view all the answers

    What is the highest occupied molecular orbital in benzene called?

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

    What is the lowest unoccupied molecular orbital in benzene called?

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

    Which of the following is a characteristic of aromatic compounds?

    <p>They have a lower energy compared to non-aromatic compounds</p> Signup and view all the answers

    Which of the following compounds satisfies all the criteria for aromaticity?

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

    What is the result of benzene reacting with bromine in the presence of a Lewis acid?

    <p>Substitution product</p> Signup and view all the answers

    How many π electrons are required for a completely conjugated, planar, 8-membered ring to be aromatic?

    <p>10</p> Signup and view all the answers

    Which of the following compounds is antiaromatic?

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

    Which of the following compounds is NOT considered aromatic?

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

    What must any structure for benzene account for?

    <p>All of the above</p> Signup and view all the answers

    Which of the following compounds is NOT considered aromatic?

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

    In pyridine, where is the nonbonded electron pair localized?

    <p>On the nitrogen atom</p> Signup and view all the answers

    Which of the following compounds satisfies all the criteria for aromaticity?

    <p>Tropylium cation</p> Signup and view all the answers

    What is the relationship between the number of MOs and the number of vertices in the inscribed polygon method?

    <p>The number of MOs is equal to the number of vertices minus one</p> Signup and view all the answers

    Which of the following compounds is not aromatic?

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

    What must any structure for benzene account for?

    <p>The presence of six pi electrons</p> Signup and view all the answers

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