Beyond Labz Assessment PDF

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Beyond Labz Assessment

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Beyond Labz Assessment

1-2: Performing a Separatory Funnel Extraction Often in organic synthesis reactions, multiple products will be synthesized that need to be separated from each other. The separatory funnel is a standard organic laboratory tool that uses differences in chemical solubility to separate compounds. All separatory funnel extractions involve a polar and a non-polar solvent. The two solvents are immiscible, meaning that they will not mix with each other.

The product mixture is added to a separatory funnel, which has a stopcock and can be sealed with a glass stopper. The product mixture is often (but not always) in an organic (non-polar) solvent. A volume of polar solvent is added to the separatory funnel which is then sealed and shaken vigorously. Products that are more soluble in the polar solvent will be dissolved into that solvent. This portion of the mixture is often called the “aqueous phase” or the “aqueous layer”. Products that are more soluble in the non-polar solvent will dissolve in that solvent, and this portion is known as the “organic phase” or the “organic layer”. After shaking, the funnel is placed in a ring stand and the solvents are allowed to settle. Because the two solvents are immiscible, they will separate into two layers, with the more dense solvent settling at the bottom. The separatory funnel is then unstoppered, and the lower layer is carefully drained into a separate flask by opening the stopcock. This layer can be the aqueous or the organic layer, depending on the solvent densities. In a real laboratory, the separatory funnel extraction is often repeated several more times to ensure the best separation of the products.

Below is a table of some common organic laboratory solvents and their approximate densities. In the real lab, it may be difficult to determine visually which layer in the extraction is which. A knowledge of the densities of the solvents will help you correctly identify the layers. Solvent

Density (g/ml) at ~20 °C

H 2O

1.000

Diethyl Ether – (C2H5)2O

0.713

Dichloromethane – CH2Cl2

1.327

In this assignment, you will be guided through the steps of a hydroboration reaction as a demonstration of how to use separatory funnel extraction as a tool to separate products. This assignment will also serve as a tutorial to teach you how to utilize the various parts of the organic simulation that will be used in later assignments. Help with using Beyond Labz Organic Synthesis can be found by clicking on the bell on the stockroom counter.

1. To start this activity, click this link for Performing a Separatory Funnel Extraction . The lab will load in a new tab. Click back to this tab to read further instructions and complete the questions below. You will see a lab bench containing reagents on the back of the bench, aqueous reagents on the right, an equipment rack containing necessary laboratory equipment, a red disposal bucket for cleaning up the lab, and the organic stockroom in the back. Other pieces of laboratory equipment will be used in other assignments.

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Beyond Labz Assessment

2. You will find a round bottom flask located on the stockroom counter. Select the starting materials for the reaction by clicking on 1-hexene in the Hydroboration menu in the Stockroom tab. Now add the solvent, ether (Et2O) from the top of the Stockroom tab. Double click on the flask to move it to the stir plate on the lab bench.

3. The starting materials you added will be listed in the Live Data Flask Contents display and hovering over a reagent will display its structure on the chalkboard.

4. In order to perform the reaction, a mixture of borane (BH3) and tetrahydrofuran (THF, C4H8O) in hydrogen peroxide (H2O2) must be added. This is done by double clicking on the BH3 bottle on the back of the lab bench. The Live Data display will now show that the reagent has been added to the reaction mixture.

5. Before the reaction can be started, we must be able to heat the reaction mixture so the reaction can proceed at a suitable rate. This is done by adding a heating mantle to heat the reaction mixture, adding a condenser so the mixture can be refluxed, and then adding nitrogen gas to maintain an inert atmosphere and to prevent pressure buildup. Double click on the Heater mantle on the bench in front of all of the reagent bottles. Now double click on the Condenser from the equipment rack. Finally, double click on the nitrogen gas hose to the right of the stir plate. Now click on the dials on the front of the stir plate to start the reaction. You should see the reaction mixture stirring in the round bottom flask. 6. Monitor the reaction by TLC and by looking at the contents of the flask in the Live Data display. Let the reaction reach completion. If you have not previously completed the activity Using Thin Layer Chromatography, please see the note at the bottom of that assignment regarding TLC in Beyond Labz.

What are the two products formed (ignore the solvent)? 1-Hexanol and Boric Acid

7.

The solvent for this reaction is ether.

Do you expect product #1 to be more soluble in ether or an aqueous solvent? Draw the structure and explain your response. Attach a picture of the structure you drew. Explanation 1-Hexanol is more soluable in ether because an organic molecule dissolves when in an organic solvent.

File - Choose File hexanol.png

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Do you expect product #2 to be more soluble in ether or an aqueous solvent? Draw the structure and explain your response. Attach a picture of the structure you drew. Explanation Boric Acid would be more soluable in an aqueous solution because it ereacts with the aqueous soluion to form B(OH-)4.

File - Choose File boric acid.png

My predictions were correct; the aqueous layer contained Boric acid while the organic layer contained the 1-hexanol.

A seperatory funnel extraction isolates components of two different solvents (with different densities) that are merged together in a liquidliquid reaction.

The ether is less dense than the aqueous solution (which in this case is water)

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If the original organic solvent was dichloromethane and water was used as the aqueous extraction solvent, which layer would you expect to be at the top and why? The dichloromethane layer would be on the bottom because it is more dense than water.

When you remove the organic layer from the separatory funnel in Beyond Labz Organic Synthesis, there is an automatic rotary evaporator step that is performed to drive off the organic solvent. The organic solvent will disappear when you move the organic layer to a new flask on the cork ring. In the real lab you would need to perform this step on your own. This will not occur when you remove the aqueous layer, however. You will need to perform a different kind of separation following the separatory funnel extraction to remove your product from water. Occasionally in organic synthesis, an ionic product is formed. In these cases, it is often necessary to supply the product mixture with an excess of protons to neutralize the ionic product. This can be accomplished by adding an acid – such as HCl – to a product mixture in a separatory funnel. Acids are aqueous and will therefore form the aqueous layer. Some lab activities in Beyond Labz Organic Synthesis will require you to do this. An important note: In Beyond Labz, when any aqueous solvent is added to the separatory funnel (e.g. H2O, HCl, or NaOH), there is also a volume of diethyl ether added. The addition of diethyl ether is not explicitly shown but does occur. This will be most notable when diethyl ether is not also chosen as the reaction solvent. In the cases where ethanol is chosen as the reaction solvent, it is assumed that the compounds in the reaction are transferred into a solution of diethyl ether (perhaps through the evaporation of ethanol and redissolution in ether). Please keep this in mind as you work through activities in Beyond Labz.

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