Postlab #7: Pinicol Rearrangement (Pavia Exp 49B) CHM 337
This is an individual report worth 30 points.
DIRECTIONS for Typed Report Typed reports should not be more than 5 pages total not including attached spectra.
Title (1 points)
Make sure to have a descriptive title. “Pinicol Rearrangement” is not acceptable
Abstract (3 points)
Provide a brief summary of the experiment and the results you obtained. Make sure to write out the overall reaction with percent yield of product. No more than one page double-spaced. Here is a brief abstract from a recent Skibo publication:
“Phenylalanine –linked pyrrolo[1, 2-a]benzimidazoles were successfully designed to target melanoma cells in vitro. Our design utilized three molecular targets: a phenylalanine pump, the reducing enzyme DT-diaphorase, and IMP dehydrogenase. We describe the synthesis of these compounds as well as the results of in vitro, in vivo, and QSAR studies.”
Note the use of the active voice above. Most scientific papers are written in the past passive voice (first sentence above), but the active voice has now become acceptable. You are welcome to use “I” or “we” in your write-ups.
Introduction (3 points)
The introduction discusses everything you knew and/or expected prior to the reaction. It should always include an overall reaction with a mechanism along with a verbal explanation. It should also include a description of how you plan to characterize your product (i.e. how will you know if your experiment was successful?)
· Draw overall reaction using a chemical drawing program
· Discuss and explain reaction and reactive species
· Discuss expected results/goals
· Discuss how you plan to characterize product. For the Pinicol Rearrangement, discuss expected spectral changes in the attached 13C-NMR spectra and how these spectra can be used to confirm that the rearrangement occurred.
· Also attach your group’s pinacolone H-NMR spectrum. Is your spectrum consistent with formation of the expected product? Provide a discussion along with peak assignments. Are there impurities in your H-NMR?
Procedure – (3 points)
No more than ½ page double-spaced. Here is an example from a published paper:
“A solution of 1 mmol of t-boc protected L-substituted-phenylalanine 5 in 15 mL of dry DCM was cooled to 00C. To this solution, 1.1 mL (1.1 mmol) of a 1M solution of 1,3-dicyclohexylcarbodiimide (DCC) was added. The resulting mixture was stirred at 00C until the solution became cloudy.” Procedures are nearly always in past passive voice, but active voice is OK.
Results and Calculations (3 points)
This is your “numbers” section. So make sure to supply the literature and experimental melting point of the product. Supply the percent yield and percent yield calculations. Tables could be useful here.
Discussion and Conclusions (3 points)
Discuss the overall experiment. The discussion should allude back to everything in the introduction as well as tie-up any unpredicted results. Be sure to discuss all sources of error and possible synthetic routes to improve the reaction and yield. A good discussion answers the questions “Did it work?”, “Should I change anything next time?” You should explain why it worked, or speculate (based on sound reasoning) why it didn’t work.
Discussion Topics and Questions (14 points) This part of the report will include answers to the following Pinicol-related questions. Some of these questions will appear on your next quiz or final.
|a)||How would you determine if your benzopinacolone product is not contaminated with the benzopinacol starting material? Provide three different techniques along with the expected findings if your product is pure or contaminated.|
|b)||What is the driving force for a pinacol rearrangement?|
|c)||Predict the major product for each of the following rearrangements:|
|d)||Provide a mechanism for the following rearrangement. Show curved arrows and intermediate structures.|