Week 5 Problem Set 30 BL (Esterification Reaction)
Useful Link: Refractometer
ATTN: answers to the below questions are due at the start of your lab period; these answers should be part of your pre-lab write-up.
1. Work-up of the reaction mixture
a. Why is the extraction be performed with NaHCO3 and not NaOH solution?
b. Why do you have to be careful in the beginning of the extraction? Show pertinent equations for the extraction with NaHCO3?
c. Why do you use a conical vial here and not a separatory funnel in this experiment?
2. A student refluxes a mixture 25.0 g of benzoic acid, 15 mL of ethanol and 1 mL of concentrated sulfuric acid for three hours. After the work-up, the student isolated 28 g of the ester.
a. Determine the yield of the reaction. Show all calculations.
b. How could the student improve the percentage yield of this reaction?
c. What would happen if he runs the reaction with 0.5 mL of the sulfuric acid?
d. The student observes refractive index of nD25= 1.5025. Which conclusion can he draw from this observation?
3. Extraction Theory (Hint: See appendix of reader)
a. Construct two different flow diagrams to separate aniline, benzoic acid and anthracene.
b. Construct a flow diagram to separate a phenol, naphthalene and methyl benzoate.
c. When performing extractions in small scale, the number of transfer steps should be minimized. With regard to this, would it be better to use a solvent that is heavier or lighter than water when extracting a compound from an aqueous layer?
d. A slightly polar organic compound distributes between an organic solvent and water with a partition coefficent of (in favor of the organic solvent). What simple method can be used to increase the partition coefficent?