OChem 2 Lab Chemical Resolution-Part B Dr PDF

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OChem 2 Lab Chemical Resolution-Part B Dr...

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OChem 2 Lab Chemical Resolution-Part B Dr. Rivero/Spring 2021

Activity 2: Resolution of Racemic (+/-)-1-Phenylethylamine (50 pts) Complete the activity and submit your work in a pdf form through blackboard course website. Please DO NOT EMAIL IT TO ME. I will grade ONLY the worksheet submitted on blackboard. Due Date: Wednesday, Feb 10 by 12:12 pm (before lab meeting start).Leaning Goals After completing this activity, the students should be able to: ● ●

Describe the resolution process for separating the (S)-1-Phenylethylamine isomer. Explain how to determine the optical rotation and the enantiomeric excess percent of the resolved enantiomer. To answer the questions in this activity, you must watch the video Resolution of (+/-)-1-Phenylethylamine by OrganicChemistry Tube, https://www.youtube.com/watch?app=desktop&v=mPzHm3QuneQ. This video shows the experimental procedure to separate a racemic mixture of (+/-)-1-Phenylethylamine into a single enantiomer by using the resolution process technique. You are also allowed to use any organic chemistry textbook and/or the libretexts resources. Make sure you review optical activity, specific rotation, enantiomeric excess, and the stereoisomeric relationship between enantiomers and diastereomers

1. Complete the following Data Sheet while watching the video. Mass of (+)-tartaric acid: 7.8 g Molar Mass of (+)-tartaric acid: 150.09 g/mol Volume of (+/-)-1-phenylethylamine: 6.6 mL Density of (+/-)-1-phenylethylamine: 0.940 g/mol Molar Mass of (+/-)-1-phenylethylamine: 121.18 g/mol Mass of the resolved enantiomeric amine:

2. Calculate the percent yield of the resolved phenylethyl amine enantiomer. Would you expect to recover the same mass of the resolved phenylethylamine enantiomer as a racemic amine

mixture? Show all your work for your calculations, reporting just the numbers will not give you

partial points. 3. Draw the structure of the resolving agent with the correct stereochemistry (R/S) used in the resolution of (+/-)-1- phenylethylamine.

4. Draw the structures of the enantiomeric mixture of (+/-)-1-phenylethylamine and assign the correct stereochemistry (R/S absolute configuration).

5. Draw the structures of the diastereomeric salt mixture and assign the correct stereochemistry (R/S absolute configuration).

6. What technique was used to separate the formed diastereomeric salts? Why cold methanol was used in this procedure? Can we use hot methanol in this separating process? Explain. The technique used to separate the formed diastereomeric salts was a process called vacuum filtration. We use cold methanol to ensure that the cooled crystals do not break apart and turn back into a liquid. If we used hot methanol, we would break apart the crystals and our data would be inaccurate. 7. Describe how to free the pure enantiomeric amine from the diastereomeric salt? What is the NaOH for? What is the purpose of the anhydrous magnesium sulfate? Which enantiomeric phenylethylamine was resolved in this process? The NaOH is used to form the free base of 1-phenylethylamine.

8. Describe how the optical activity of the resolved amine was measured? And, Calculate the specific rotation of the resolved amine?

9. Using the literature value for the pure enantiomer, calculate the enantiomeric excess (% ee) of the resolved amine.

10. Besides the Polarimeter method, what other technique could you use to calculate the percent optical purity (%ee)? Explain. High performance liquid chromatography is another technique you could use to calculate percent optical purity. HPLC pumps a sample mixture in a solvent at a high pressure through a column with a chromatographic packing material....