Cyclohexane Conformations and Strain
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Questions and Answers

What is the major organic product of the bromination of cyclohexene?

  • Dibromocyclohexane with one chiral center
  • Trans-dibromocyclohexane
  • A racemic mixture of dibromocyclohexane (correct)
  • Cis-dibromocyclohexane
  • How would you characterize the configuration of the starting alkene, cyclohexene, prior to bromination?

  • E configuration
  • Neither E nor Z (correct)
  • Z configuration
  • Both E and Z configuration
  • What is the stereochemical relationship of the products formed from the hydroboration-oxidation of an alkene?

  • All products are meso compounds
  • Products could be racemic mixtures or diastereomers (correct)
  • All products are identical enantiomers
  • Products have alternating stereocenters
  • When performing bromination at −5°C in CCl4, what type of interactions mainly govern the reaction mechanism?

    <p>Electrophilic additions</p> Signup and view all the answers

    In the context of stereochemistry, what should you include when drawing product structures from the given reactions?

    <p>Complete structural representations including wedge-and-dash bonds</p> Signup and view all the answers

    Which structure is expected to have the most angle strain?

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

    Among the following chair conformations of cis-1,3-dimethylcyclohexane, which two are in equilibrium?

    <p>Conformation C and Conformation D</p> Signup and view all the answers

    What is the relationship between two conformations that are considered conformational enantiomers?

    <p>They are mirror images of each other.</p> Signup and view all the answers

    What would be the expected difference in boiling points between two stereoisomers of 1,3-cyclohexanediol?

    <p>One will have a higher boiling point than the other due to polarity.</p> Signup and view all the answers

    When considering two chair conformations of α-(+)-glucopyranose, which conformation is typically the more stable one at equilibrium?

    <p>The conformation with equatorial substituents.</p> Signup and view all the answers

    How do stereo specific properties like solubility differ between stereoisomers?

    <p>Solubility can vary based on the arrangement of functional groups.</p> Signup and view all the answers

    What type of strain is primarily associated with eclipsed conformations?

    <p>Torsional strain</p> Signup and view all the answers

    What type of relationship exists if two chair conformations are identical?

    <p>They are identical conformations of the same molecule.</p> Signup and view all the answers

    Study Notes

    Angle, Steric and Torsional Strain

    • Angle strain is caused by deviation of bond angles from ideal values (e.g., 109.5° in tetrahedral structures)
    • Steric strain is caused by repulsion between non-bonded atoms or groups
    • Eclipsing strain (torsional strain) is caused by repulsion between electron clouds of eclipsed bonds

    Chair Conformations

    • Cis-1,3-dimethylcyclohexane has two chair conformations: the conformer with both methyl groups in equatorial positions and the conformer with one methyl group axial and one equatorial

    Conformational Diastereomers

    • Conformational diastereomers are conformations of the same molecule that are non-superimposable mirror images
    • Conformational diastereomers have different energies and can be interconverted by rotations around single bonds

    Cyclohexane Conformational Stability

    • In cis-1,3-dibromocyclohexane, the more stable conformer has both bromine substituents in equatorial positions

    Relationship between Structures

    • Two structures might be conformations of the same molecule, conformational diastereomers, conformational enantiomers, or identical
    • If two structures are not conformations of the same molecule, they might be diastereomers, enantiomers

    Properties of Stereoisomers

    • Stereoisomers can have different physical properties such as boiling point, density, solubility, optical rotation, and dipole moment
    • Taste can be influenced by chirality

    α-(+)-Glucopyranose

    • α-(+)-Glucopyranose has two chair conformations, one more stable than the other
    • The more stable conformation has the largest number of bulky groups in equatorial positions

    Bromination of Alkenes

    • Bromination of alkenes can lead to the formation of stereoisomers (diastereomers or enantiomers)
    • The stereochemistry of the product(s) depends on the configuration of the starting alkene (E or Z)

    Hydroboration-Oxidation

    • Hydroboration-oxidation of alkenes can lead to the formation of alcohols
    • The stereochemistry of the product(s) depends on the configuration of the starting alkene

    Hydrohalogenation

    • Hydrohalogenation of alkenes follows Markovnikov's rule: the hydrogen atom adds to the carbon atom with the most hydrogen atoms
    • The stereochemistry of the product(s) depends on the configuration of the starting alkene
    • The reaction can be influenced by the presence of a tertiary carbocation intermediate.

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    Description

    This quiz covers key concepts related to angle, steric, and torsional strain in cyclohexane and its chair conformations. It also explores the principles of conformational diastereomers and their stability in various configurations. Test your understanding of how these factors influence molecular structure and stability.

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