Orgo Lab-1 - organic chem lab 1 PDF

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Simona Kogan Organic Chemistry Lab 1, Section: 1 TA: Shambeda

Lab performed: 9/9/19 Report due: 9/16/19

Experiment 4A: Determination of a Partition Coefficient for the System Benzoic Acid, Methylene Chloride, and Water Objective: The purpose of this lab will be to learn fundamental lab skills such as using the electronic balance, automatic pipets, pasteur filter pipet, and using a vortex to determine the partition coefficient of benzoic acid at the microscale level. Experimental Procedure: The procedure was followed as described in Mayo, pages 144-145, with the modifications listed in the posted Canvas document. Additional modifications to the procedure included the following: ● 9 Fluorenone will be used instead of benzoic acid. ● Will use 75 mg of 9-fluorenone and 1.0ml of methylene chloride and water during the initial addition. ● The transfer of methylene chloride will be done through a glass pipet, not a filter pipet. The solution will be transferred to a test tube rather than another 5-ml conical vial. Anhydrous sodium sulfate will be used at this stage instead of magnesium sulfate. ● Used a heater block to concentrate the final, dried methylene chloride solution. We also had to add a boiling stone the vial before obtaining the tare weight. Removed the sodium sulfate through filter piper. Data and Results:

9-Fluorenone

Methylene Chloride

Water

Mol. Formula

C13H80

CH2CL2

H20

Amount (mg)

0.083 1.0

1.0

Amount (ml) mmoles

0.4606

Molar mass

180.20

84.93

18.02

Density (g/ml)

0.93

1.33

1.00

Melting Point (Celcius)

80-83

-96.7

0

Boiling Point (Celcius)

163-166

40

100

Weight of tare with rock: 11.582 grams After evaporation: Trial 1: 11.616 grams Trial 2: 11.604 grams Trial 3:11.596 grams Trial 4: 11.594 grams Observations: ● The mixture of 9-fluorenone, methylene chloride and water created a two layer liquid solution. The water remained on the top while the organic mixture stayed on the bottom (yellow) ● Had to do multiple rinses was not enough methyl chloride ● Solution did not crystalize on the bottom (anhydrous salt) which indicates that there was little to no water after doing the separation ● Had to do 4 heatings and weight continued to drop ● When it evaporated the solution that was left was dark yellow Calculations: 9- Fluorenone in CH2CL2= (final weight of vial +boiling stone+ solid)- (weight of vial +boiling stone) 11.594g-11.582g=0.012 grams=12 mg 9-Fluorenone 9-Fluorenone remaining in aqueous layer= (original mass of 9-Fluorenone)(9-Fluorenone in Methylene chloride) 0.083g-0.012g=0.071g= 71mg in aqueous layer 9- Fluorenone Kp CH2CL2/H20= (9-Fluorenone in methylene chloride)/ (9-Fluorenone in H20) Kp= 0.012g/0.071g=0.169

1. Drawing:

B. Non polar regions- London Dispersion Forces C. Labeling D. Polar regions- London Dispersion, Dipole-Dipole, Ion- Dipole E. 9-Fluorenone will be more soluble in Methylene Chloride because Fluroenone is more nonpolar than polar because of the Carbon atoms that are present; therefore, the more carbon atoms a molecule the more non-polar it will be. Methylene chloride is non polar and water is polar (like dissolves like) resulting in 9-Fluorenone to be more soluble in methylene chloride. F. Even with some experimental error the partition coefficient is consistent because the solution separated into 2 layers. This resembled when I saw the bottom layer was 9-Fluorenone and methylene chloride. The top layer was water mixed with 9-fluorenone. This shows that there was distinguishable layers and if it was not consistent then it would appear all mixed together (homogenous).

2. Sodium sulfate is used as a drying agent and its purpose was to absorb any remaining water left over from the organic layer which was then used to determine the amount of 9-Fluorenone that was dissolved in the organic layer. 3. It is not necessary to accurately weigh the sodium sulfate because the amount isn’t important because it is used to absorb the water left over in the organic layer so it can be filtered out completely. The problem associated with putting to little amount of sodium sulfate could mean water being left over which could skew the results and increase the weight. (The more clumps on the bottom showed there is still water). However, if used to

much of sodium sulfate would result in difficulty in extracting the 9-Fluorenone and result in a smaller weight. 4. The first error could be having 9-Fluorenone left over on the sides of the test tubes and pipettes and not filtering out with enough methylene. This would result in a larger mass of 9-Fluorenone in the aqueous layer and cause the partition coefficient to lower. Another error could be not heating the methylene chloride solution long enough which would result in a higher mass because their would be extra aqueous solution causing an increased mass and lower partition coefficient. This could potentially mean the trials are not close enough together which skews the results. 5. A. Ethylene chloride would form the bottom layer B. Ethylene would be on the bottom because of its density. Since, its density is higher than both water and 9- Fluroenone will cause it to sink to the bottom; similarly to methylene chloride with the water. C. This is because it is more dense which will cause it to sink to the bottom. Also, because it has a lower boiling point

Works Cited: Mayo, D. W.; Pike, R. M.; Forbes, D. C. Microscale Organic Laboratory with Multistep and Multiscale Syntheses, 5th ed.; John Wiley & Sons, Inc., 2011; pp 141-145. Modifications for Expts 4A: Partition Coefficient Part A, Canvas document....