3 component Lab Report PDF

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Autumn Sicard CHEM 345 Lab, Section 01 WSU Vancouver

Abstract The solubility of the three compounds, benzoic acid, ethyl-4-aminobenzoate, and 9fluorenone was demonstrated by a separatory funnel and the process of extraction. Each compound was neutralized to be able to be dissociated while the other two remained insoluble. This process allowed each component to be individually removed with little error. The results were shown once each component was dried and weighed to determine the percent recovery. The first compound, benzoic acid, had a 45.3% recovery. The second compound, ethyl-4aminobenzoate, had a 42.3% recovery. And the last compound, 9-fluorenone, had a 118% recovery. Introduction Extraction is the separation of components from a solid or liquid into a different solvent or phase. By using a separatory funnel and knowing acid/base chemistry, the three components in this lab can be successfully separated into layers, separated from each other, and weighed to determine the percent of the component that was recovered. The purpose of this experiment is to learn extraction techniques for separating and purifying organic compounds, learning how acid/base chemistry is related to solubility, and how to calculate percent recovery. Experimental First, a powdered mixture of benzoic acid (C7H6O2), ethyl-4-aminobenzoate (C9H11NO2), and 9-fluorenone (C13H8O) are placed into a clean separatory funnel. It is important that the funnel’s stopcock is closed before adding anything to it. Second, add approximately 20 mL of diethyl ether ((C2H5)2O) to the mixture and seal the funnel. Invert the funnel, keeping the cap secured, and briefly shaking the solution to completely dissolve the compound mixture. Third, add approximately 20 mL of 3M hydrochloric acid (HCl, pH < 0), seal the funnel, and repeat the mixing process. Open the stopcock to vent the pressure build up in the funnel. Continue shaking vigorously and vent periodically for 30 seconds. Fourth, allow the two immiscible layers to fully separate and then drain the bottom layer into an Erlenmeyer flask (50 mL) and label it as “acid extract”. Repeat the same process using 3M sodium hydroxide (NaOH, pH > 14) draining the bottom layer into a flask and labeling it as “base extract”. Drain the remaining ether into a third flask and label it as “neutral extract”. Fifth, take the acid extract and slowly add 8 mL of 6M NaOH then continuing to add drops until litmus paper shows a shift from red to yellow/blue. Repeat the same process with the base extract using 6M HCl to neutralize until litmus paper shifts from blue to yellow/red. Sixth, weigh and then place a filter paper in a Buchner funnel, dampen the paper with distilled water, and hook up the vacuum hose to the funnel. Slowly pour the acid extract into the funnel and filter the precipitant. Remove the filter paper with the

precipitant and repeat the filtering process with the base extract on a new and pre-weighed filter paper. Seventh, the isolated compounds are taken and carefully transferred to two larger pieces of pre-weighed filter paper and placed into a drawer, along with the neutral extract, to dry overnight. The samples must be exposed to air to fully dry. Finally, once the samples appear fully dry, weigh and determine percent recovery. Dispose of all waste in their designated waste containers. Results In this experiment, the goal was to determine the percent recovery of each component in the mixture. This can be calculated by determining the amount of each component that was extracted from the original mixture. The percent recovery can be determined by dividing the recovered mass by initial mass and multiplying that by 100. The data can be seen in the table below: Extraction of 3 Component Mixture Component Benzoic acid Ethyl 4-aminobenzoate 9-fluorenone

Initial Mass (g) 0.333 0.333 0.333

Recovered (g) 0.151 0.148 0.393

Discussion The starting chemical, benzoic acid, is not soluble in water. The addition of sodium hydroxide makes it soluble in water and here is how that works. Benzoic acid nonpolar because it has no acidic hydrogens that can form hydrogen bonds. Water is polar, therefore a nonpolar compound like benzoic acid will have a very difficult time trying to dissolve in a polar compound (like dissolves like). When combined with NaOH, the H+ atom on the benzoic acid will break off and attach to the OH- ion to form the product water (H2O, not pictured in image below). Then the Na+ atom will be attracted to the now negatively charged oxygen on the benzoic acid ring. This results in the product of sodium benzoate. Sodium benzoate is water soluble because it is polar. It is polar because the oxygen atoms are much more electronegative than carbon and hydrogen atoms. These partial charges are focused on one side of the molecule, resulting in an overall polar molecule. This base extract reaction is pictured below:

+ H2O When ethyl 4-aminobenzoate is combined with hydrochloric acid, the resulting product is combined with sodium hydroxide to produce the reaction shown below. Ethyl 4-aminobenzoate

is partially soluble in water. The ring structure and ethyl ester are both nonpolar and therefore insoluble in water. Although the NH2 group readily forms hydrogen bonds and wants to dissolve in water. This makes the overall compound dissolve only a small amount in water. Conversely, when added with HCl, ethyl 4-aminobenzoate forms an ionic salt which is incredibly soluble. These acid extract reactions are shown below:

The last compound, 9-fluorenone, has no acid/base chemistry because it is a neutral component. Conclusion The pKa values also have a role to play in this experiment. The lower the pKa, the stronger the acid and the more the compound will dissociate and vice versa. In this experiment, benzoic acid (pKa = 4.20), ethyl-4-aminobenzoate (pKa = 2.51), and 9-fluorenone (pKa ≈ 30.2) are separated through layers. The use of a separatory funnel can be used to separate and examine each substance in a mixture. The percent recovery for each substance is: -

Benzoic acid = 45.3% Ethyl 4-aminobenzoate = 42.3% 9-fluorenone = 118%

The percent recovery of 9-fluorenone being over 100% is most likely because of the lower percent recoveries of the other substances. The extraction method may have been less accurate than desired or the loss during filtration. Post-Lab Questions 1. What is the pKa of each of the three compounds used in this experiment? a. See conclusion 2. Given that aqueous conditions have a pH range of 0-14, why is a pKa of 30 not of interest in extractions using aqueous conditions? (remember that pKa refers only to acidity of a molecule)

a. The pKa value is relates with Ka because pKa = -log (Ka). Since the pKa approximately equals 30.2 then the Ka is equal to 10-30.2. Therefore, a high pKa value creates a small dissociation which means it cannot deprotonate in an aqueous solution. 3. How did the pKa of each component play a role in this experiment? a. If one of the components is acidic, a basic solution must be added to neutralize and make it soluble by increasing its polarity while the other components remain insoluble. 4. How did changes in pH alter the polarity of ethyl-4-aminobenzoate? a. The change in pH will make the compound become polar or nonpolar depending on the protonation or deprotonation of the NH 2 group (explained why in discussion). By adding a low pH solution (HCl), the amine protonates and becomes polar. By adding a high pH solution (NaOH), the amine deprotonates and becomes nonpolar. 5. Why is the p Ka of fluorenone different than that of most ketone compounds? a. 9-fluorenone has all its carbons tied up in double bonds and has no available acidic hydrogens. Therefore, this makes the pKa of the molecule much greater than other ketones. 6. Give an example how the principles illustrated in this lab apply to everyday life. a. Ways the techniques in this lab are used in everyday life is in the production of essential oils. For example, an orange has a nonpolar structure and its oil can be extracted from its rind into an organic solvent. Other methods of extracting oils can be through transferring compounds from layers and then selective removal of compounds. References Nichols, Lisa. “4.3: Uses of Extraction.” Chemistry LibreTexts, Libretexts, 14 Aug. 2020, chem.libretexts.org/Bookshelves/Organic_Chemistry/Book:_Organic_Chemistry_Lab_Tec hniques_(Nichols)/04:_Extraction/4.03:_Uses_of_Extraction. CHEM 345 Laboratory Handout, "Title of Handout" (author unknown), 2016....