Problems Set - Meeting #4
Announcements:
1. Make sure that you make progress on your formal report as well in terms of literature search and writing the parts that you completed already in the lab.
2. The second quiz will be administered on Thursday, October 9, 2008 at 11:00:00 am covering the resolution and the ligand synthesis and techniques involed in these projects. Bring a ruler, non-graphing calculator and pen with you. Please make sure that you arrive on time (this also applies to the morning sections!). Late arrivals will not be allowed into the class room since they disturb the rest of the class!! This also means that you will not be allowed to take the quiz!!!
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. Galactose is of the monosaccharide that make up lactose. It is less sweet than glucose and is often coined as "brain sugar".
a. A student isolates the a-D-form of galactose and obtains the optical rotation for a solution of 0.3 g in 5 mL of water. The student observes an optical rotation of a= +9.0o in a 10 cm cell. Determine the optical purity of the sample.
b. The student measures the same solution again (which was kept in a closed container) the following day and observes an optical rotation of a= +4.8o in the same polarimetry cell. Rationalize this change.
2. Referring to the synthesis and characterization of the Jacobsen ligand, answer the following questions.
a. The initial stage of the reaction the tartrate salt is reacted with potassium carbonate in water. Provide a balanced equation and rationalize the choice of solvent.
b.A student only isolates 0.4 g of the aldehyde. Which adjustments does he have to make to his setup?
c.After the initial part of the reaction (see a.), 95% ethanol is added. Explain why.
d.Why is water added to the reaction mixture prior allowing it to cool to room temperature?
e.The ligand exhibits a fairly strong intramolecular hydrogen bond. Give three pieces of evidence for this observation.
f. The ligand is bright yellow in color. Why?
g. Which solvent is used to acquire the UV-Vis spectrum of the ligand? Which type of cuvette should be used here?