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. Why is it advisable to exclude water from the reaction as much as possible? How is this accomplished?
b. In the lecture it was emphasized that the the alcohol is used in excess in this reaction. How much is used and explain briefly why.
c. What is function of the concentrated sulfuric acid? Show the appropriate intermediate. How much should be used?
d. At the end of the reaction, the air condenser is replaced by the Hickman head. Which purpose does this serve?
e. After the reaction is terminated, the reaction mixture is chilled and ice-cold water is added. Which purpose does this step serve and in which container should this step be performed?
f. Why is the reaction mixture extracted with sodium bicarbonate during the work-up? Show pertinent chemical equations. How does the student know that he is done with this step?
g. How is the crude product purified?
2. A student refluxes a mixture of 2.99 g of phthalic acid, 4.00 mL of n-propanol and 1.00 mL of concentrated sulfuric acid for two hours. After the work-up, the student isolated 3.60 g of the ester.
a. Show a balanced chemical equation for the reaction.
b. Why is a relatively large amount of sulfuric acid neceassry in this reaction?
b. Determine the yield of the reaction. Show all calculations.
c. Predict the boiling point of the product at p = 30 torr.
d. The student observes refractive index of nD25= 1.3842. 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.
3. Thermodynamics
Perform an AM1 calculation (see meeting 4, Check the Freq. and Thermodynamics box in the Calculation menu ) for the following molecules: Acetic acid, ethanol, ethyl acetate and water. Retrieve the following information from the Display-Output option: Heat of formation and Total Entropy. Based on this data, calculate the equilibrium constant for the reaction.