INDEPENDENT Makeup Assignment for Thermodynamic Vs. Kinetic Control Lab
Due April 8, 2020
Assignment: Read the Organic Letters paper from 2009 entitled “Origin of
Thermodynamic versus Kinetic Control of Allene Hydroboration with 9Borabicyclo[3.3.1]nonane and 10(R)-Trimethylsilyl-9-Borabicyclo[3.3.2]decane” and
answer the following questions.
1. Summarize, in your own words, what the Ess and Roush Groups studied in this
2. In a hydroboration reaction, which product (E or Z) is expected to form?
3. Why is this product expected?
4. Draw the two possible products that can form (Scheme 1).
5. Give the reference for the paper where it was shown that (Z)-crotyl-10-TMS-9borabicyclo[3.3.2]decanes are more thermodynamically stable.
6. Give the specific reaction being studied.
7. What led the group to study allene hydroboration?
8. How are they studying this reaction (i.e. what methods are they using)?
9. Which product, Z-3 or E-3, requires less energy to form?
10. Give one reason this product is observed.
11. What is the structure of 9-BBN?
12. What does the phrase “Z-E hydroboration selectivity” mean?
13. Describe the TS that converts Z-3 into E-3.
14. What does it mean to be “kinetically favored”?
15. What causes the increase in barrier for the rearrangement of Z-7?
16. In Scheme 4a, what is the most thermodynamically stable product Z-5 or E-5?
17. In Scheme 4a, what is the most thermodynamically stable product Z-7 or E-7?
18. In Scheme 4a, which is the kinetically favored product, Z-5 or E-5?
19. In Scheme 4a, which is the kinetically favored product, Z-7 or E-7?
20. Label the energy profile below for the reaction of 1a and 2b.
21. What causes the large barriers for TS-Z9 and TS-E9?
22. Does the Si atom of the TMS group affect the barrier of TS-Z7?
23. If yes, how does it affect the barrier. If no, why does it not affect the barrier?
24. How many boat/chair conformations of the borabicyclo auxiliary exist?
25. What do the authors conclude the cause of kinetic control to be?
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