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 esterification is an equilibrium reaction which exhibits a relatively low Keq. Which problem is the experimenter going to face if he starts with a 1:1 mixture of the acid and the alcohol?
b. In the lab the alcohol is used in excess in this reaction. How much is used in terms of molar ratio? Rationalize this ratio.
c. Why is concentrated sulfuric acid added to the reaction mixture? Show the appropriate intermediate assuming the student uses benzoic acid . How much sulfuric should be used in the reaction?
d. The reaction mixture is refluxed. What does this mean and how is this accomplished in the lab?
e. After the reaction is terminated, the mixture is chilled and water is added. What does the experimenter look for in this step?
f. Afterwards the reaction mixture is extracted with sodium bicarbonate Show pertinent chemical equations. How does the student know that he is done with this step?
g. The crude ester purified by vaccum distillation. How is this done and which concept does this method use?
2. A student refluxes a mixture of 2.50 g of succinic acid anhydride, 4.00 mL of ethanol and 0.50 mL of concentrated sulfuric acid for two hours. After the work-up, the student isolated 3.70 g of the ester.
a. Show a balanced chemical equation for the reaction.
b. Determine the yield of the reaction. Show all calculations.
c. Predict the boiling point of the product at p= 40 mmHg.
d. The student observes refractive index of nD23= 1.4190. Which conclusion can he draw from this observation?
e. Predict the 1H-NMR spectrum for the product. Include the multiplicity, the chemical shift and the integration in the table.