Organic Chemistry Lab 2 [Extraction]

This lab was interesting to say the least.

Lab 2: Extraction
Experiments: 4B, 4C, 4E
Lab Teqniques : 12.1-12.6, 12.8-12.10

Experiment 4B
Procedures:
1- Measure out 0.05g of either Sodium Benzoate, Succinic Acid, or Benzoic Acid and place in conical vial [5ml]
2- Add 2.0ml Methylene Chloride and 2.0ml water to vial
3- Shake with rocking motion for 1min
4- Let stand until no emulsion is left and there are 2 seperate layers
5- Pipette out the bottom organic layer into a clean conical vial
6- Add a appropriate ammount of Sodium Sulfate to the vial so that the drying agent doesn't clum that much and has pieces floating around when shaken
7- After either 15 min or untill the solution is clear or the drying agent doesn't clump indicating a dry solution (covered)
8- Then transfer the dry solution to a weighed conical vial without transfering the drying agent as well
9- Heat the conical vial uncovered in a hot water bath until the solution evaporates
10- Weigh Vial after cooling and find out how much was in the vial (sample)

For this lab I did the Sodium Benzoate. I measured out 0.055g of compound and then I went and

did all the steps. I ended up okay with the Pasteur pipettes even though I have a problem with those. The

interesting part was after step 9. My vial in particular had some minute brown stain (2 =>1mm) at the

bottom of the vial but upon weighing the vial which was 22.117g empty it came out the same mass as

before. My lab instructor said that the mass was probably so small that it was negligible. Another 2 students

in lab performed the experiment with the Succinic Acid and the Benzoic Acid. For the Succinic Acid the

were worse than mine in a way. The other student didn't have anything in the conical vial at all. The only

succesful extraction with a appreciable ammount of compound transfered to the organic layer was the

Benzoic Acid. The compound transfered to the organic layer for that student came out to be 0.039g.

As for an explanation of why this happened it is arbitrary. I have a hypothesis that it was the fact that

the Sodium Benzoate and the Succinic Acid may have been less soluble in Mehthylene Chloride than in

water. Dr.Bob said that this hypothesis of why the compounds didn't travel into the Methylene Chloridee

would have been the same as his. He said that that 1g of Succinic Acid dissolves in 13ml of water and is "practically insoluble in petroleum ether, CCl4, somewhat soluble in acetone and etc." For the Sodium

Benzoate the reason for the low yield in the end would have been according to Dr.Bob, that fact that "Sodium Benzoate..is a highly polar compound and is VERY soluble in water." In addition to that the reason it would

have been attracted to the water more so than the Methylene Chloride would have been the fact that Sodium Benzoate is a h