Kaya Brown- lab 1 (1)

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Kaya Brown CHEM 2203 Section 4 Experiment 4A 1/23: Assessing the Partition Coefficient of 9-Fluorenone in Both Methylene Chloride and Water. Objective The objective of this experiment is to determine the partition coefficient in two immiscible solvents; methylene chloride and water. Various laboratory techniques will be used such as weighing milligram quantities of materials, dispensing microliter volumes with automatic pipette, and filtering through a glass pipet to demonstrate this method. This experiment strives to investigate how solvent extraction techniques can be applied to separate mixtures in the lab. Experimental Procedure Before beginning the experiment, ensure that two clean test tubes as well as a 5ml conical vial are obtained. Pre-weigh one test tube with a boiling stone and set it aside. Weigh the measured mass of 9-fluorenone and add to the conical vial, along with 1ml of water and methylene chloride. Swirl vial to dissolve 9-fluorenone and allow layers to separate. Once separated, obtain a glass pipet and slowly draw up the methylene chloride layer without disturbing the aqueous layer. Dispense the methylene layer into the unused test tube, then carefully estimate the amount of sodium sulfate that will remove residual water and add to the test tube. While this solution is to “dry” for 10-15 minutes, add a small piece of cotton in a glass

pipet to act as its filter. Funnel the solution through the cotton into the tared test tube containing the boiling stone. To ensure that all of the solution has been transferred through the cotton, you may rinse the sodium sulfate to transfer any product left on its surface or retained in the cotton. Place this test tube on a heating block and remove when all the methylene chloride has evaporated. Upon evaporation, allow the 9-fluorenone to form a solid and record its weight. Place the tube back into the heating block and repeat this process until its mass difference becomes less than 10mg, or 0.01g. Use this data to calculate the partition coefficient and clean station when finished. The procedure was followed as described in pages 144-145 of the lab manual, Microscale Organic Laboratory with Multistep and Multiscale Syntheses, with the modifications listed in the Canvas document. Additional modifications made in the lab that differ from the instructions within the manual include the following. Experimental Modifications ● The process involving the transfer of the methylene chloride layer will use a basic glass pipet, instead of a filter pipet. The transferred solution will then be placed into a test tube, as opposed to another 5-mL conical vial. ● To transfer all remaining methylene chloride through the glass pipet containing a small cotton ball, a bulb was placed at the top of the pipet to squeeze out the remnants. ● The temperature at which the methylene chloride solution was dried using a heater block was 90 degrees celsius. Reaction Scheme

Data/Results 9-fluorenone Methylene Chloride Water Mol. Formula C13H8O CH2Cl2 H2O Amount (mg) 0.0776 Amount (mL) 1.0 1.0 mmoles 0.43 11.77 0.70 Molar Mass 180.2 84.93 18.02 Density (g/L) 1.13 1.33 1.0 Mp ( ℃ ) 80-83 Bp ( ℃ ) 40 100 Observations ● Water and methylene chloride separated upon mixing into a clear layer above and yellow layer below. ● An estimated amount of sodium sulfate was added carefully until all water bubbles disappeared from solution. ● The sodium sulfate and methylene chloride mixture began to solidify slightly after 10 minutes of heating. ● Two more consistent measurements were taken after heating the solution twice more. ● Upon the last heating, the solution became a yellow solid. Calculations 9- Fluorenone in CH2CL2= (final weight of vial +boiling stone+ solid)- (weight of vial +boiling stone) 13.35g -13.27g = 0.08g = 80 mg 9-Fluorenone

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9-Fluorenone remaining in aqueous layer= (original mass of 9-Fluorenone)- (9-Fluorenone in Methylene chloride) | 0.0776g - 0.08g = 0.0024g | = 2.4mg in aqueous layer 9- Fluorenone Kp CH2CL2/H20= (9-Fluorenone in methylene chloride)/ (9-Fluorenone in H20) Kp= 0.08g / 0.0024g = 0.0333 g Questions 1. Draw the chemical structures of 9-fluorenone. Use it to answer the following solubility-based questions: a) Circle and label all regions of each molecule that exhibit non-polar behavior. b) These non-polar regions interact with solvent molecules with what types of intermolecular forces (list all that apply): hydrogen bonding, dipole-dipole, dipole-induced dipole, or induced dipole-induced dipole (London dispersion)? London dispersion and dipole-induced-dipole interactions. c) Circle and label the region of each molecule that exhibits polar behavior. d) This polar region interacts with solvent molecules with what types of intermolecular forces (list all that apply): hydrogen bonding, dipole-dipole, dipole-induced dipole, or induced dipole- induced dipole (London dispersion)? H-bonding, dipole-dipole, and dipole-induced-dipole interactions. e) Based on the answers to parts (a)-(d), predict whether 9-fluorenone will be more soluble in

methylene chloride (a more non-polar organic solvent) or water (a very polar solvent). Explain your answer. Based on the observed nonpolar properties of 9-fluorenone, it has a larger nonpolar region that will interact with the methylene chloride, thus being more soluble in the organic layer. f) Was your experimental partition coefficient consistent with the prediction in part (e)? Yes, the calculated kp of 0.0333 g is greater than 1, meaning that 9-fluorenone proved to be more soluble in the methylene chloride. 2. Chloroform, CHCl3 (119.38 g/mol, density = 1.49 g/mL, bp = 61.2 °C), is an organic solvent with polarity similar to methylene chloride, and is also not miscible with water. a) If substituted for methylene chloride in this partition coefficient experiment, would chloroform form the top or bottom layer? b) Provide an explanation, using appropriate data to support your answer. Chloroform would form the bottom layer because like methylene chloride(density = 1.33 g/ml), it is denser than water. Chloroform has a density of 1.49 g/ml while water has a density of 1.00 g/ml. c) Despite the similarities, methylene chloride is more commonly used than chloroform as an extraction solvent. Why? While both chloroform and methylene chloride are considered toxic, methylene chloride is generally regarded as less toxic compared to a carcinogen like chloroform. Methylene chloride also has a higher volatility than chloroform. This means that it evaporates more quickly, which can be advantageous in extraction processes because it makes the removal of the solvent easier and quicker. 3. Consider the structure of anthracene-9-carboxylic acid (see below). Compare it to the structure

of 9-fluorenone. This structure has a very similar nonpolar region to 9-fluorenone and an additional hydroxyl group attached to its polar region, creating a carboxylic acid group. This carboxylic acid group increases the polarity of anthracene-9-carboxylic acid. a) If this experiment is performed with anthracene anthracene-9-carboxylic acid in place of 9-fluorenone, would the partition coefficient be higher or lower than the partition coeff. obtained for 9-fluorenone? Anthracene-9-carboxylic acid is likely to have a higher partition coefficient in the polar phase compared to 9-fluorenone, so a lower kp overall. This is because the carboxylic acid group increases its solubility in water. b) Provide an explanation to support your answer for part a. Include the types of intermolecular forces involved in each case. Within its polar region, anthracene-9-carboxylic acid has intermolecular forces such as hydrogen bonding, dipole-dipole forces and stronger induced dipole-dipole interactions. These will allow the structure to interact better with water compared to 9-fluorenone, due to the increased polarity and potential for ionization of the carboxylic acid group. 4. An organic compound has a partition coefficient of 3.5 between methylene chloride and water. If 45 mg of this compound is added to a conical vial containing 2mL of water and 2mL of

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methylene chloride, how much of this organic compound would be in each layer after the mixture is thoroughly mixed? 45 - x / x = 3.5 Methylene chloride layer = 35 mg Water layer = 10 mg

Work 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.