ORGANIC CHEMISTRY 2

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ORGANIC CHEMISTRY 2

• SPRING 2005
• MID-TERM EXAMINATION - SOLUTIONS

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• Write a mechanism for each of the following
  reactions, paying attention to stereochemistry
  where appropriate.
• Note this does NOT mean for you to add you own
  reagents or conditions because you could not work
  out the problem as set.
• Doing a different problem will invariably score
  zero

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• Addition is cis and concerted

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• The other BH bonds react similarly

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• In BR3 we still have an empty pz orbital at boron

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• Predict the product(s) of the following
  reactions, paying attention to stereochemistry
  where appropriate. Full credit may be obtained
  for the correct product, but partial credit may
  be obtained for a mechanism heading in the right
  direction if the product is wrong.

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• Protonate each of the following alkenes to give
  the most stable carbocation.

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• How would you accomplish the following
  conversions? They require more than one step.

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• Identify the sites of electrophilic mononitration
  of each of the following

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• Treatment of 1-bromo-2-deutero-2-phenylethane,
  with strong base leads to a mixture of deuterated
  and non-deuterated phenylethenes in which the
  deuterated product predominates by approximately
  71. Explain.

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• The mechanism is E2 as shown. C-H/C-D broken in
  RDS. C-H broken 7 times as fast as C-D to give
  more of the product in which deuterium is
  retained.

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• A reacts 20 times faster than B when treated with
  KNH2/liq NH3.

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• Br is a better leaving group. Therefore the
  elimination to give the benzyne, which is the
  RDS, is faster for the bromide.