see doc
The following series of reactions were carried out by Phillips and Kenyon and reported in 1923. Starting from the same compound, two reaction sequences were carried out. These sequences resulted in the synthesis of 3A and 3B. However, the enantiomeric purity of 3A and 3B is not the same. This suggests that the reaction mechanism are not the same. Your task is to create a presentation showing your proposed mechanisms of the reactions, answering the questions, and narrating an explanation of your work.
1) Prepare neatly hand-written pages for the your mechanisms in the two pathways. Each step should be on a separate page, including push-arrows and transitions states. For example, the reaction of
1 with KH should have its own page.
2) Prepare additional pages for questions. Show your work.
3) Present a narrated presentation of your pages. This is what you will submit. This can be as simple as recording a video with you phone, explaining the pages.
If you wish, you can incorporate the page images into a Power Point and add narration or use the Kaltura app on Brightspace. It is up to you, but the pages must be neatly hand written, and there must be an audio narration.
Compounds
1,
2 and
3B are pure enantiomers. Compound
3A is a mixture of enantiomers. Pay attention to the optical rotations, as this gives insight into the reaction mechanism(s). The zig-zag line in
3A indicates a mixture of enantiomers.
1. For compound
1, determine the R or S designation. Show how you assigned priorities, and arrived to the configuration you selected.
2. Propose reaction mechanism(s) for both pathways. Be sure to include the push-arrows and transition state(s) in your mechanism.
3. Given your proposed mechanism, did the chiral center of the starting material
1 in Pathway B undergo retention, inversion, racemization, or partial racemiziation?
4. Given your proposed mechanism, did the chiral center of the starting material
1 in Pathway A undergo retention, inversion, racemization or partial racemization?
5. What specific optical rotation would you expect for
3A, if it were the pure enantiomer of
3B?
6. Calculate the %ee of
3A. Show your calculations.
7. Did your mechanism for Pathway A explain the results in terms of optical purity/enantiomeric composition? If not, you need to come up with another mechanism. Hint: It is possible for a single reaction to have two different mechanisms simultaneously.
