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 procedure asks to make sure that the glassware is dry in this experiment. Why?
b. Why is the alcohol used in excess in this reaction? How much of an excess is used in the lab?
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 in an ice bath and ice-cold water is added. A precipitate forms at this point. Which conclusion can the student draw from this observation and how should he proceed?
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. Why should the joints be lubricated before performing the vacuum distillation?
2. A student refluxes a mixture of 3.43 g of anthranilic acid, 4.80 mL of n-propanol and 2.00 mL of concentrated sulfuric acid for two hours. After the work-up, the student isolated 4.10 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 = 40 torr.
d. The student observes refractive index of nD25= 1.5542. 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. After reviewing the Extraction chapter in the SKR, take the online quiz
(http://bacher.chem.ucla.edu/TakeQuiz/?id=c51ce410c124a10e0db5e4b97fc2af39). The quiz is worth 10 points, and has to be taken until 1 hour prior to the in-lab meeting during week 6. (Hint: In some cases more than one answer is correct!) Even though you can take the quiz until one hour prior to meeting 2 of your section, you should not delay taking it since there might be some problems with the server. There seem to be problems with some MAC systems as well. After you submit the answers, your score should appear on your screen. If this does not happen, you will have to retake the quiz. (There will not be any possibility to retake the quiz weeks later!).
In order to take the quiz, you have to go through a UCLA ICP address. This means that you either have to use your Bruin-Online account or go through the VPN (Vitual Private Network, software can be found here: http://www.bol.ucla.edu/services/vpn/) to have this UCLA ICP address. To log in, use your last name and your student ID. If you are experiencing problems, contact the instructor via email and include your full name (indicated which one is your last name), your student ID and section .