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4:142 Exam. I (100 pts) Name:_______________________ Section:_____
* For all answers, use only the space provided in the question.
* You have 50 min. * We believe that questions with a mark are more difficult than others.
* At the end of the test, there are NMR correlation tables.
1. Separation methods:
a. Extraction:
(6 pts) fill in the missing parts (marked by *).
(5 pts ) How many extraction steps (washes) are needed to extract at least 99.8% of compound X from solvent A to B if it is 4 times more soluble in B? Show work.
Mixture containing a natural organic compound
and basic and acidic im purities
waste
waste
1. Dry
2. Concentrate
Pure, natural, organic
compound
organic phase aqueousphase
aqueous phase
organic phase
*extract with___________________
and separate layers
*extract with___________________
and separate layers
b. TLC: (5 pts) When you try to run (develop) a TLC for Caffeine with 1/ Methanol/CH 2 Cl 2 – it doesn’t run (by the end of the run, the spot is still on the “starting line”). What should you change to make it run?
c. Distillation:
(3 pts) Define Boiling Point.
(3 pts ) A compound boils at 145 ˚C but decomposes at 110 ˚C. How can you purify it by distillation?
2. Acetaminophen: p- aminophenol reacts with acetic anhydride to yield p- amidophenol acetate (acetaminophen). In the laboratory, you first dissolved the p- aminophenol in HCl, then heated the solution in hot water bath, and added basic buffer (sodium acetate) and acetic anhydride. a. (5 pts) Why did you have to add HCl in the first place? Please write the chemical reaction for this stage.
b. (10 pts) Why did you have to add sodium acetate before adding acetic anhydride?
c. (5 pts) Which atom is the nucleophile and which atom is the electrophile in this amidation reaction?
5. NMR:
a. 1) (5 pts) What does Fourier Transformation (FT) do?
b. (15 pts) Propose a structure and assign hydrogens to peaks for each of the compounds whose spectrum is shown below:
