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5.E: Cycloalkanes (Exercises)

  • Page ID
    201131
  • These are homework exercises to accompany Chapter 4 of Vollhardt and Schore's "Organic Chemistry" Textmap.

    4.7: Carbocyclic Products in Nature

    Practice Problems

    Q21

    Draw all of the different structures with the formula C6H12 with only one ring and name them.

    Q22

    Draw all of the different structures with the formula C7H14 with only one ring and name them.

    Q23

    Name each of the following structures.

    Q24

    Draw the following structures, and if the name is not in accordance with IUPAC naming, give the proper name.

    (a) isopropylcyclohexane (b) 1,1-dimethylcyclobutane (c) cyclobutylcyclopentane (d) cyclopropylpropane (e) 1-iodo-4-chlorocyclohexane (f) 1-ethyl-2-cyclobutane

    Q25

    Draw the following structures, no indication of the ring conformation is necessary.

    1. trans-1-bromo-2-methylcyclohexane
    2. cis-1-bromo-2-methylcyclohexane
    3. trans-1-bromo-2-iodocyclopropane
    4. 1-bromo-2-iodocyclopropane
    5. 1-fluoro-4-methylcycloheptane

    Q26

    Given that the ideal bond angle for an sp3 hybrdized carbon is 109.5o and that the ideal angle for an sp2 hybridized carbon is 120o, what radical is the most stable based on the angle strain? Is the radical more stable than the previous cycloalkane, again based on angle strain alone? (Hint, a transition from an sp3 hybridized to an sp2 hybridized carbon occurs).

    (a) cyclobutane (angle=88o) (b) cyclopropane (angle=60o) (c) cyclohexane (angle ~ 109.5o)

    Solutions

    S21

    S22

    Notice how many more different structures that can be drawn for C7H14 than C6H12. If more than one ring were an option, even more structures could be drawn.

    S23

    S24

    S25

    S26

    Given that the ideal bond angle for an sp3 hybrdized carbon is 109.5o and that the ideal angle for an sp2 hybridized carbon is 120o, what radical is the most stable based on the angle strain? Is the radical more stable than the previous cycloalkane, again based on angle strain alone? (Hint, a transition from an sp3 hybridized to an sp2 hybridized carbon occurs).

    (a) cyclobutane (angle=88o)

    • Before the radical forms: 109.5-88= 21.5o
    • After the radical forms: 120-88= 32o

    The radical creates more ring strain

    (b) cyclopropane (angle=60o)

    • Before the radical forms: 109.5-60=49.5o
    • After the radical forms: 120-60=60o

    The radical creates more ring strain

    (c) cyclohexane (angle ~ 109.5o)

    • Before the radical forms: 109.5-109.5=0
    • After the radical forms: 120-109.5=10.5o The radical creates more ring strain

    The cyclohexane radical is the most stable based on angle strain alone