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Objective: To gain a better understanding of how to separate organic compounds from water using steam distillation, building upon concepts from our last lab on distillation. We will be extracting the natural product from plants through the process of vaporization through high-pressure and high-temperature processes.
Compounds of Study:
Dichloromethane
Dichloromethane
Chemical Formula: (CH2Cl)
Boiling Point: (39.6°C)
Molar Mass: (84.93 g/mol)
Image from Sciencemadness.org
Isolate Euganol
Isolate Euganol
Chemical Formula: (C10H12O)
Boiling Point: (254°C)
Molar Mass: (164.2 g/mol)
Image from PubChem
Pre Lab:
High-end perfumes are very expensive because the natural products used to create the scent are very expensive. Even though steam distillation is an effective way to isolate such products, what do you think the price of such products means about the efficiency of the isolation?
The cost of high-end perfume leads me to believe that isolation is not very efficient.
2. Most of the desired products are terpenoid in character. They belong to a class of compounds known as the terpenes. Conduct an image search of terpenes and describe in good detail what structural component that all terpenes have in common.
Terpenes are cyclic in nature and are primarily made up of carbon with a grouping on the first carbon structure.
3. In a paragraph (4-5 sentences), describe how the process of steam distillation works.
Steam distillation allows us to separate compounds and water. When water is boiled in a distillation
apparatus, the steam is brought into a condenser, the vapor is brought to a condenser. When both substances cool, the water is collected in the condenser and the other compound remains behind in the original boiling container. Steam distillation is often used when the boiling point of the second substance is higher than the boiling point of water to ensure that the second substance stays behind in the boiling container.
4. The amount of a natural product that is “carried” by steam depends upon the molecular math of the product. Solve for the following scenario using the equations presented in the text. A mixture of ethyl iodide (CH3CH2I, bp 72.3 °C) and water boils at 63.7 °C. What weight of ethyl iodide would be carried over by 1 g of steam during steam distillation?
See image below!
5. Sometimes the molecular weight of the natural product being isolated is not known. It is important to know the molecular weight so that the product can be identified. Using the same equations, one can solve for this mass. Consider the following scenario - the condensate from a steam distillation contains 8 g of an unknown compound and 18 g of water. The mixture steam distilled at 98 °C. What is the molecular weight of the unknown?
See image below!
6. Extraction is described as a partitioning. This is exactly how we describe what happens during TLC – the material partitions between the mobile phase and the continuous phase. In extraction the partitioning is between two liquid phases.
A. Considering that your two solvents are water and dichloromethane, if the natural product material partitions into the dichloromethane, what does that mean about the polarity of the compound? Briefly explain.
The natural product material is likely non-polar. We know that dichloromethane is a nonpolar compound and because "like compounds partition with like compounds," we can assume that the natural compound is also non-polar.
B. Will the partition coefficient/distribution coefficient be greater than 1 or smaller than 1? Briefly explain.
The partition coefficient/distribution coefficient will be greater than 1. We know this due to its partitioning with dichloromethane, which means it has a density that is greater than water.
7. You will have two layers within your separatory funnel, what do you need to know about the two phases in order to determine which is forming the top layer and which is forming the bottom layer?
The solvent with the greater density will be on the bottom of the funnel and the solvent with the lesser density will be on top.
8. What are the seven steps for using the separatory funnel?
Add dichloromethane to the separatory funnel. The amount used should be about 1/3 of the volume of the distillate.
Place the cap on the separatory funnel and invert the funnel about 20 times for it to complete mixing. Open the stopcock every 4-5 inversions to release pressure.
Allow the layers to settle. If an emulsion forms, add a small amount of saturated salt solution.
Take the stopper off the separatory funnel and drain into two Erlenmeyer flasks.
Add a small amount of dichloromethane to each flask to test which sample is dichloromethane.
Add magnesium sulfate to the dichloromethane layer until the solid no longer appears to "clump.
Filter the magnesium sulfate from the dichloromethane layer by gravity filtration and evaporate the dichloromethane layer under vacuum pressure using heat.
9. The only time one holds a separatory funnel in their hands is during mixing. What is the proper way for the separatory funnel to be secured at other times?
Using a ring stand.
10. Although dichloromethane is not soluble in water, because there are polar bonds, there can be dipole-dipole interaction between dichloromethane and water. A small amount of water therefore is going to dissolve into the dichloromethane. Magnesium or sodium sulfate is added because it is a solid hygroscopic material. What is a hygroscopic material and therefore what is its purpose in the extraction process?
Hygroscopic materials absorb water. By adding a hygroscopic material to a solution after it has been distilled, we are able to move any excess water from the substance, allowing us to filter out the purest possible product.
Problem 4
Problem 4
Problem 5
Problem 5
Procedural Steps:
Experimental:
Obtained 20 grams of pre-measured clove in a round bottom flask and filled the round bottom flask containing cloves halfway with DI water.
Set up a steam distillation experiment according to the image provided below.
Placed 700 ml of DI water in the steam-generating flask.
Filled the round bottom flask containing sage to the halfway mark using DI water.
Filled the condenser with water
Weighed the flask that will contain the solution, weight of the flask was determined to be 127.38 grams.
Set the hot plate setting to eight and the heating mantle setting to 45. After 35 minutes the steam-generating flask began to boil.
The first droplet of distillate was obtained 44 minutes after the experiment began.
Carefully monitored the solution until 150 ml of distillate had been obtained. It took 1 hour 30 minutes to collect all of the distillate.
The aqueous distillate was then placed into a separatory funnel with 50 mL of dichloromethane.
The funnel was inverted approximately 20 times, venting every 4-5 times to reduce any pressure that had built up in the funnel.
After inverting some emulsion occurred. To reduce emulsion, 20 mL of a saturated salt solution was added.
The funnel was set to rest for about 5 minutes until two distinct layers formed.
The layers were removed and separated into two separate flasks.
Dichloromethane was added to each flask to determine the organic and aqueous layers. The layer the dichloromethane was miscible in was determined to be the organic layer which also contains the natural oil.
The organic layer was transferred into a Buchner flask which was then connected to a vacuum.
The flask that is connected to the vacuum was then placed on a hot plate which was set to a heat level of 4 and was moved in circles until a yellow and thick substance was formed that smelled strongly of clove.
The flask was then removed from the heat and the oil was weighed.
The oil was then dotted on a TLC plate and placed in a solvent for TLC analysis.
Results:
Observations:
The oil extracted from the cloves was a yellow/brown color with a strong clove scent. The oil felt warm immediately after being extracted but eventually came to room temperature after being allowed to sit. Once evaporated from the solvent, the pure oil had an increased viscosity. The mass oil was about 1/20th of that of the total organic solution.
The clove oil extracted was analyzed using TLC. The extract and was placed into a TLC place and placed in a TLC chamber, two dots appeared on the plate when examined under the UV light.
Results:
The total amount of clove oil extracted by steam distillation was 1.14 grams. The percent yield with an original mass of 20 grams and a recovered mass of 1.14 grams is 5.7% (%yield = (recovered mass/original mass)*100=(1.14/20)*100=%5.7).
By examining the TLC plate (as shown in the image below), it is observed that the solvent from the chamber traveled 4.5 cm from the starting line. By examining the two dots under UV light we see that spot 1 the shorter/smaller smear, traveled a total of 1.7cm from the starting line when analyzing the midline of the spot, giving it an RF value of 0.378 (RF1=(1.7/4.5)=0.378. Spot 2, the longer/larger spot traveled a total of 3.6 cm when examining the midline of the spot from the starting line, giving it an RF value of 0.8 (RF2=(3.6/4.5) = 0.8).
Discussion:
The percent recovery for the extracted clove oil for this lab was very small. This correlates with current information about how difficult it is to extract pure oils from natural compounds as this process is very complex and has low yield. The complexity and low yield of extraction is of particular importance in the perfume industry, leading to the high cost of high-end products and fragrances.
The TLC analysis presented two spots under the UV light. The presence of these two spots indicates that the extraction of the oil was able to isolate two different distinct terpenes. The smaller spot on the TLC plate is a polar substance. Due to the solvent being a non-polar substance, the spot that only existed towards the beginning of the analysis was a polar substance as it wasn't miscible with the non-polar solvent which would cause the spot to stop further down on the TLC plate. This was also shown by the spot's RF value as it was very small which corresponds with its polar characteristics.
The spot near the top of the TLC analysis however was non-polar as it traveled with the solvent. This was probably the isolate eugenol as it displayed strong non-polar characteristics and created a dark and large spot. This is further shown by the RF value for that spot being closer to 1 which indicates a non-polar substance.
Conclusion:
Even with high precision in extracting pure oils, the low yield of this laboratory procedure leads to increased costs of fragrances and perfumes.
Reflection:
In this lab, I learned about how oils can be distilled from a solid compound using steam. I practiced laboratory techniques including steam distillation system set-up, extraction using a separatory funnel, evaporation, and TLC. I particularly enjoyed working with materials that I was familiar with and seeing how processes are performed to create the products that I use on a regular basis.
This lab had to be repeated as my partner and I initially evaporated our oil while going through the evaporation procedure. We lost a lot of the product we had collected, resulting in a low yield and a poor sample for TLC analysis. When this experiment was repeated my partner and I took special care to keep the temperature of the hot plate low to prevent accidental evaporation and associated loss of product. My partner and I learned a lot about the importance of being aware of the expected boiling points for all chemicals in a solution and how these values will change when substances are mixed together.
If I had to repeat this lab again, I would make sure to monitor my hot plate settings throughout all parts of the experiment. By keeping the distillate on a lower hot plate setting for a longer duration of time, it is possible that the yield for my experiment would increase, allowing for more pure oil to be collected.
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