Orgo Ch 3 notes pt 2

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DesLee26
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238344
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Orgo Ch 3 notes pt 2
Updated:
2013-10-02 10:32:07
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CHM 201
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  1. Are rings flat?
    yes, but not really
  2. What is the only flat ring that is saturated?
    the three membered ring
  3. A flat ring system has __. Why?
    angle strain due to desire to be 109.5 degrees
  4. In cyclopropane, all __ lie outside an imaginary triangle.
    electron densities of sigma bonds
  5. How strong are the sigma bonds attached? (cyclopropane)
    barely hanging on
  6. In cyclopropane, sigma overlap is __
    usually very weak to exist (weaker than normal)
  7. Cyclopropane has __ and __.
    • angle strain
    • torsional strain
  8. What is the only way for cyclopropane to exist?
    in eclipsed conformation because there are two carbons attached to one carbon
  9. Why does it have to planar?
    three points form a plane
  10. Heat given off in reactions is somewhat indicative of __.
    ring strain
  11. Rank the cycloalkanes by their relative ring strain.
    • 3 and 4 membered rings: highest
    • 5: not so much
    • 6: most stable (perfect ring system; lowest in energy)
  12. Cyclobutane
    - shape
    - to alleviate tension, it __
    - if __, it would be __.
    • not a square or planar, more like a butterfly
    • puckers
    • perfectly eclipsed, it would be perfectly square or planar
  13. Cyclopentane
    - __ most comon ring size in nature (__)
    - what is the most common?
    • 2nd most common
    • 4-5%
    • cyclohexane
    • 90%
  14. Cyclohexanes go through __ and __.
    • chair conformations
    • ring flipping
  15. Explain axial and equatorial.
    • axial: parallel to imaginary axis that goes traight at or away from me
    • equatorial: parallel to the molecule itself; to some equator
  16. If the chair conformation has wedges, then what?
    the wedges are coming at you
  17. Even though you flip the chair, what?
    your molecules stay up or down. The axial will  become equatorial and vise versa. Cis remains cis. Trans remains trans
  18. True or False:
    cis and trans are the same as axial and equatorial.
    • false:
    • have nothing to do with them
  19. True or False:
    cyclopropanes react
    true
  20. Explain reactivity in terms of cyclobutane.
    not terribly rective in the form of a saturated molecule
  21. Explain reactivity in cyclopentane.
    • not the best because it isn't flat
    • if flat all the H eclipse the other around the ring
  22. axial bonds
    parallel and alternate up and down
  23. equatorial bonds
    come in three sets of two parallel lines; each set is also parallel to two ring bonds; alternate between sides around the ring
  24. Explain rules of flipping chair comformations.
    • all axial become equatorial
    • all equatorial become axial
    • all up bonds stay up
    • all down bonds stay down
  25. __ are flagged by parallel H's __
    • gauche interactions
    • 1,3 diaxial interactions

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