Objective
In lab 3, we need to use steam distillation to extract pure Eugenol from cloves. In lab 4 part 1, we should aim for the highest quality pure crystallization of acetylsalicylic acid from aspirin. In part 2 of lab 4, our objective is to obtain a comparable pure crystallization of benzil from an impure benzil mixture.
Materials
The objective of lab 3 was to extract Eugenol from 75 g of cloves using various solvents and equipment. Water and Dichloromethane were used as solvents, Calcium Chloride as the drying agent, hydrochloric acid as the acid, and Sodium Hydroxide as the base. The equipment used included a thermometer & holder, separatory funnel, classen adapter, 3-way adapter (distillation adapter), triple neck round bottom flask, west condenser, vacuum adapter, Erlenmeyer flask, 500ml & 50 ml beaker, Bunsen burner, rubber tubing, clamp holder & extensions, and graduated cylinder.
For both parts of lab 4, the hot plate was used as the heating source. The substances were heated in a 100ml Erlenmeyer flask and then filtered using filter paper and a funnel with a neck. Beakers, a vacuum flask for additional filtration, and an electronic scale for weighing the crystals were also used. The solvent used for both parts was 95% Ethanol, which was also dripped on the crystals for purification. In part one, ten tablets of aspirin were used, while in part two, two grams of impure benzil were used.
Procedure
In Lab 3, we embarked on a complex experiment that consisted of several steps. Our first task was to acquire 75 grams of cloves and place them inside our triple neck round bottom flask.
We added 200 ml of water to the flask and sealed two of the three necks with stoppers. We placed a Classen adapter into the remaining center neck. In one of the other necks, we placed a separatory funnel, filled with 50 ml of water. In the last neck, we inserted a 3-way adapter. On top of the 3-way adapter, we inserted a thermometer and its holder to measure vapor temperature. We connected the side of the 3-way adapter to a west condenser, which was then inserted into a vacuum adapter. The vacuum adapter was positioned above an Erlenmeyer flask to collect the distillate.
The setup used clamp extensions and holders to support the triple neck round bottom flask and the vacuum adapter, ensuring stability and preventing vapor leakage. The triple neck flask was placed above a Bunsen burner for heating. The water in the flask was heated to boiling point while taking precautions to prevent foaming. The objective was to distill 60 ml of distillate. Once around 30 ml of distillate was collected, an additional 50 ml of water was added from the separatory funnel to keep the cloves submerged.
After collecting the entire 60 ml of distillate, our next step was to remove the water. To do this, we transferred all of the distillate into an empty separatory funnel. We then added 15 ml of Dichloromethane to the funnel and inverted it, causing two layers to form. We released the pressure and drained the organic material from the bottom layer of the funnel into a separate collection beaker. We repeated this process three times. Additionally, we took a 5 ml sample of the Eugenol, which was not yet pure, from the collection beaker for separate experimentation and for weight comparison.
After drying with Calcium Chloride, the remaining impure Eugenol was weighed and stored for later experimentation. The impure Eugenol was then treated with Sodium hydroxide three times in a separatory funnel, following the principle of inversion and releasing pressure. From the two layers formed, we discarded the lower Dichloromethane layer and kept the top aqueous layer each time.
After deprotonating Eugenol in the aqueous layer, it was acidified using Hydrochloric acid. The pH value of the remaining Eugenol was tested using litmus paper. To extract the Eugenol, 15 ml of Dichloromethane was added three times, with each addition followed by inverting and draining the bottom layer. The Eugenol-Dichloromethane mixture was then boiled on a hot plate in a collection jar to evaporate the Dichloromethane. The pure Eugenol obtained was weighed. In the first part of lab 4, we purified ten aspirin tablets and used 10 ml of 95% Ethanol as our solvent.
In an Erlenmeyer flask, the tablets and Ethanol were combined and heated until gently boiling. To prevent bubbling and ensure complete dissolving, the mixture was swirled. The objective was to obtain a transparent liquid with suspended white solid particles. Once achieved, the contents of the flask were filtered using a narrow-necked funnel into a small beaker and allowed to cool to room temperature. Throughout the filtration process, caution was taken to avoid any floating solids from passing through. During cooling, observation was made for any indications of crystallization.
After the beaker reached room temperature, it was transferred to an ice bath for faster crystal formation. Once we confirmed that the crystals had reached their peak, we filtered them and allowed them to dry on filter paper placed in a funnel atop a vacuum flask. Air was continually removed during this drying process. To ensure even distribution, we used ethanol drips to wash and spread the crystals onto the filter paper using a spatula. Finally, after waiting approximately 10 minutes, we scraped off and weighed the dried crystals.
All utensils were prepared for the second part of lab 4. In this second part, we followed a similar procedure with some variations in the solutes used. We took 2.0 grams of impure benzil and mixed it with 10 ml of Ethanol. The identical procedure from part 1 was repeated in part 2. However, our objective in part 2 was to observe a transparent liquid with suspended black powder, unlike what we saw in part 1. Additionally, in part 2, we kept the crystals obtained for future experimentation at a later date.
Class notes
Steam distillation is an effective technique for separating two compounds that do not mix, such as water and oil or Benzene and water. This situation arises because Benzene is a non-polar organic solvent, while water is a polar inorganic solvent. These compounds cannot be mixed due to their contrasting properties. When a substance undergoes vaporization, its vapor pressure must match the applied pressure, causing the liquid to transform into gas. If two immiscible compounds possess equal vapor pressure, they will also have equivalent boiling points. For example, water and naphthalene demonstrate this phenomenon where water reduces naphthalene’s boiling point. The process of boiling water generates steam.
Steam can be utilized for extracting particles through steam distillation, particularly for immiscible compounds. In our scenario, water acts as the solvent, while the cloves serve as the solutes, potentially containing Eugenol oil, which possesses anesthetic properties. To extract the contents of the cloves, they can be boiled using the Gaffney principle of intense heating. By subjecting a cell to high temperatures, it will undergo lysis, causing the release of its internal contents. Eugenol is primarily composed of a benzene ring, hydroxyl group, and methyl group, forming an organic molecule.
The substance Acetyl Eugenol is found in cloves and is derived from a compound called Eugenol. The boiling point of Eugenol is 255 degrees centigrade. One method to purify a solid through crystallization involves using a solvent that can dissolve the solute when heated to its boiling point (reflux). Ethanol, Acetonitrile, Hexane, and Toluene are commonly used solvents for this purpose.
Using water as a solvent is not recommended because of its inorganic and polar properties. An ideal solute does not dissolve at regular room temperature but only dissolves in a heated solvent. If the solute doesn’t dissolve, add more solvent gradually to the heated mixture. When there are no visible particles of the solute left in the mixture, it means complete dissolution. Sometimes, even after dissolution, certain impurities like charcoal may still be visible and floating in the solvent.
Organic compounds are typically colorless or yellow. It is crucial to filter the solvent promptly after dissolving the solute to remove unnecessary impurities. The mixture can be cooled down to room temperature after filtration to facilitate crystallization. If there is an insufficient amount of crystals formed at room temperature, placing the solvent in an ice bath can aid in this process. Filtration can then be used to separate the crystals from the solvent. Ethanol is a suitable choice for washing and drying the crystals without causing them to dissolve when maintained at room temperature.
Our lab involves the use of two solutes: Aspirin and impure Benzil. Aspirin contains Acetylsalicylic acid as its active ingredient, and a binder as its inactive ingredient. At room temperature, Aspirin does not dissolve in Ethanol. However, if Ethanol is brought to a reflux, Aspirin can be dissolved. Once dissolved, the binder will remain floating and needs to be filtered out. Each tablet of Aspirin has 325 mg of active ingredient. We will use 10 tablets, which should ideally yield 3.25 grams (100% yield). When working with impure Benzil, Ethanol can also be used as the solvent.
When Ethanol is heated until it starts to boil and the vapor is condensed and returned to the reaction vessel, the Benzil will dissolve and only its impurities will be left behind. These impurities consist of charcoal particles, which are identifiable due to the black color of the residue that floats on the surface. The removal of these impurities is a simple process that involves filtering the mixture using a funnel and filter paper.
Observations
During the steam distillation lab, we observed that the water & clove mixture turned dark brown when brought to a reflux. As the distillation process proceeded, we noticed a white milky substance floating in the collected distillate. The milky substance was oil, while the remaining component was water.
Upon addition of Dichloromethane to the mixture, an oil layer formed and separated from the water layer. The organic layer settled at the bottom while the inorganic layer rose to the top. To dry the organic layer, Calcium Chloride was used, which caused white particles resembling small Styrofoam specks to float on its surface. After removing and evaporating the Dichloromethane, Sodium hydroxide treatment resulted in two distinct layers forming.
The mixture consisted of two layers: Dichloromethane on the bottom and an aqueous oily white layer on the top. We added Hydrochloric acid to the remaining aqueous oily layer and used litmus paper to test the pH level, which turned pink. The mixture was then treated with Dichloromethane again, resulting in two layers. We separated the organic layer and evaporated the Dichloromethane, which produced a yellow thin film of Eugenol oil. In the crystallization lab, we observed a milky liquid when the aspirin dissolved in refluxing Ethanol.
After the complete dissolution of aspirin, a floating residue of white binder was observed. Subsequently, the binder was filtered out, resulting in a clear liquid. Crystallization initiated as the liquid approached room temperature. Particularly abundant crystal growth was observed when the mixture was placed in an ice bath. The filtered crystals exhibited a white color. In the case of impure benzil crystallization, dark impurities (charcoal) were observed floating on the solution’s surface. Removal of these impurities led to the identification of a yellow, clear liquid that remained.
The crystals obtained via filtration from the yellow liquid were also yellow in color.
Results
75 grams of cloves resulted in obtaining 0.05 grams of pure Eugenol oil, while 10 tablets of Aspirin, amounting to 3.25 grams of Acetylsalicylic acid, provided a yield of 0.94 grams. Furthermore, from 2.02 grams of impure Benzil, we obtained a yield of 0.03 grams of pure benzil.
Discussion
Using steam distillation, we obtained a yield of 0.05 grams of Eugenol oil from 75 grams of cloves (potential Eugenol oil). This brings up a question: why was our yield so small?
A few factors may decrease our yield capacity. These include a lack of control and the use of impure chemicals. Lack of control can manifest in various ways such as poorly fastened joints or leaky thermometer holders, which allow vapors to escape. Additionally, the absence of a vacuum-sealed system can expose the experiment to temperature fluctuations. Moreover, using impure glassware might contaminate the experiment. Furthermore, inadequate reflux of the water/clove mixture can result in reduced pickup of Eugenol by vapor particles. Lastly, a poorly calibrated weighing apparatus can also contribute to diminishing our yield capacity.
Impure chemicals, such as reagents and solvents, can hinder the pure isolation of Eugenol from cloves. For example, impure Calcium Chloride would hinder the drying process, Dichloromethane would not effectively separate Eugenol from water, Sodium Hydroxide would not deprotonate enough Eugenol, and Hydrochloric acid would not sufficiently acidify Dichloromethane for separation. In the crystallization experiments, we obtained only .4 grams of aspirin from 10 tablets, which is significantly less than the ideal 3.25 grams that could have been isolated in a perfect experiment. Similarly, in the crystallization of Benzil, we isolated only .03 grams from the original 2 grams of impure Benzil. These poor results lead us to question what went wrong. Once again, lack of control and use of impure chemicals appear to be the main factors contributing to our unsatisfactory outcomes.
- Insufficient desired solute dissolving in the solvent
- Non-dissolved solute being filtered along with impurities
- Crystallization during filtration causing the filtering of crystals
- Rapid temperature drop at room temperature trapping impurities
- Possible loss of crystal parts during drying in vacuum flask
- Poor isolation of desired substances due to impure solutes or solvents
