Week 7 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. Reaction planning of esterification carried out in the lab
a. The Fischer esterification is an equilibrium reaction that generally exhibits relatively low Keq-values. What are the consequences for the reaction carried out in the lab? Explain briefly.
b. Why is concentrated sulfuric acid used in this reaction? Show the appropriate intermediate.
c. Why is water added after the reaction mixture is cooled down?
d. Why is the reaction mixture extracted with sodium bicarbonate during the work-up? How does the student know that he extracted often enough? Show pertinent equations.
e. What is the purpose of the vacuum distillation in the last step?
2. A student refluxes a mixture 1.80 g of m-toluic acid, 3.00 mL of ethanol and 0.5 mL of concentrated sulfuric acid for two hours. After the work-up, the student isolated 1.75 g of the ester.
a. Show a balanced chemical equation for the reaction.
b. Determine the yield of the reaction. Show all calculations.
c. The student observes refractive index of nD25= 1.5020. Which conclusion can he draw from this observation?
d. Predict the 1H-NMR spectrum for the product. Include the multiplicity, the chemical shift and the integration in the table.
e. How many signal would the 13C-NMR spectrum show for the product?
3. Extraction
a. Construct a flow diagram to separate o-cresol, benzoic acid and naphthalene.
b. Construct a flow diagram to separate ethyl benzoate, acetophenone and benzoic acid.