CHEM 2211 Lab Final: Labs 4-6

What is the name and specific percentage of the hydrogenation catalyst used in today's experiment?

10% Palladium on Carbon

What solvent system will you be using to dissolve the common analgesics in preparation for TLC spotting?

1:1 methylene chloride and ethanol.

Name the four active ingredients that we will be testing in today's lab:

Acetaminophen, acetylsalicylic acid, ibuprofen, and caffeine

Acetone is an organic solvent in which all three components of the 3-component mixture are soluble. Why would it not be a good substitute for dichloromethane in this experiment?

Acetone would not be a good substituent because it is miscible with water.

During your extraction, you become confused as to which layer is the organic and which is the aqueous. How would you identify them experimentally?

Add a few drops of distilled water to each layer. If it separates, the layer is organic, if it doesn't separate it is aqueous.

Separation in a TLC Experiment

As the mobile phase moves up the TLC plate, the unknown compounds will partition between the mobile phase and the stationary phases. The fractionating will cause a separation to take place between the compound in the mixture.

What is the liquid/volatile product of this reaction?

Benzene

Palladium on Carbon (Pd/C)

Catalyst.

What specific compound is used to filter the catalyst from the reaction mixture after the reflux period is finished?

Celite

Celite

Celite was used for filtering, it caught impurities.

What compound serves as the source of hydrogen for this experiment?

Cyclohexene

Identify which of the following solvents in each pair would constitute the "upper" layer in a liquid/liquid extraction solution. If layer separation would not be observed, indicate this by stating "miscible." Ethyl acetate and 6M sodium hydroxide solution (aq): Diethyl ether and water:

Ethyl acetate and 6M NaOH are miscible. Diethyl ether will be the top layer and water will be the bottom layer.

What solvent system will you be using to "develop" your TLC plate in today's experiment?

Ethyl acetate with 0.5% acetic acid.

What would be the result of failing to mark the solvent front after developing a TLC plate? Would this affect your ability to calculate component Rf values? Why or why not?

Failure to mark the solvent line on the developed TLC plate would result in not being able to measure the distance traveled by the solvent. This would affect your ability to calculate Rf values because the formula requires that information.

Describe how TLC could be used to monitor a reaction's progress (product & byproduct formation) in a research/teaching laboratory.

First, develop the TLC plate containing the reactants. After starting the reaction, take samples of the by products and develop them as well. Next, take the products, after the reaction is complete, and develop them on other TLC plates. Lastly, compare the TLC plates to see how the reaction progressed.

Mobile Phase

Flows through the stationary phase and carries the components of the mixture with it. In this lab the mobile phase was in the liquid state, and the compound used was ethyl acetate.

What solvent is used to wash the reaction residue through the filter paper?

Hexane

What would happen if your origin line was oriented so low on the TLC plate that when it was lowered into the TLC chamber it was positioned below the level of the developing solvent (eluent)?

If the origin line were to fall below the developing solution level, the mixtures being tested would flow from the TLC plate into the developing solution rather than up the TLC plate.

Why must you remove the separatory funnel stopper prior to opening the stopcock and draining out the lower layer?

If the stopper isn't removed, a vacuum will build above the liquid causing the lower level of fluid to stop draining.

Polarity of the Solvent

In polar solvent, the more polar compounds will separate further and go higher on the TLC plate than less polar compounds.

Liquid bromine is a dark maroon/brown color. 1,2-dibromo alkanes, on the other hand, are colorless. What would it mean and why, if you added liquid bromine to your final transfer hydrogenation product and the resulting mixture converted from dark maroon to clear upon heating? Be detailed in your answer.

Liquid bromine was used to break alkenes. If you add liquid bromine to the final product and it becomes clear, then it reacted. A reaction means double bonds are breaking, therefore, your original transfer hydrogenation was incomplete.

In which solvent are all the components of today's mixture soluble?

Methylene chloride

Bronsted Base

Proton acceptor.

Bronsted Acid

Proton donor.

Retention Factor (Rf)

Rf represents the ability for a compound to move along a TLC plate when the TLC plate is developed in a specific solvent system. Rf values are calculated by measuring the distance that TLC spot moves and dividing that by the distance that the solvent moved. Rf values will not change from the TLC experiment to experiment so if you know the Rf values of a series of known compounds, you can use these Rf values to determine whether an unknown is present or not.

Unknown compound Q is spotted on a TLC plate that is then developed in cyclohexane. The solvent front is measured at 5.2 cm and the distance traveled by compound Q is measured at 3.4 cm. A sample of acetaminophen is spotted on a TLC plate that is then developed in cyclohexane. The solvent front is measured at 4.15 cm and the distance traveled by acetaminophen is measured at 2.70 cm. What can be determined about the identity of compound Q in light of this data

Rf value of Q=0.65 Rf value of acetaminophen=0.651 The identity of Q is most likely acetaminophen because their Rf values are almost the exact same. Other known substances may need to be tested to make sure.

Define Rf. What specific measurements will be used to calculate it during today's experiment?

Rf value represents the ability for a compound to move along a TLC plate when the TLC plate is developed in a specific solvent system. Rf = distance (spot)/distance (solvent)

Provide the names and structures of the compounds in today's experiment that are insoluble in aqueous sodium hydroxide. Explain why this is so:

The compounds are benzocaine and diphenylmethanol. They don not combine with NaOH to produce water or water soluble salts.

Provide the names and structures of the compounds in today's experiment that are insoluble in aqueous hydrochloric acid. Explain why this is so:

The compounds are benzoic acid, o-toluic acid, 2-methoxybenzoic acid, and diphenylmethanol. They do not combine with HCl to form water or water soluble salts.

Cyclohexene

The hydrogen donating reagent.

Olive Oil States through this experiment

The olive oil was a liquid because it was unsaturated at the beginning of the experiment. After hydrogenation, it became saturated and a solid.

Which solution will comprise the bottom layer in today's experiment? Will the composition of the aqueous solution change this relative positioning during the course of the separations?

The organic layer will be on the bottom. The acid/base will not not change the position.

Stationary Phase

The phase of a chromatography system on which the materials to be separated are selectivity absorbed. In this lab the stationary phase was in the solid state, and the compounds used were acetaminophen, acetylsalicylic acid, caffeine, and ibuprofen.

Lab 6: Transfer Hydrogenation

The purpose of this lab is to preform transfer hydrogenation on olive oil to produce shortening. Transfer hydrogenation is the process of using organic molecules as a hydrogen source to transfer hydrogen to other molecules. Unsaturated fats can be turned into saturated fats using this method.

Lab 5: Separation of Three Component Mixture (Acid/Base Extraction)

The purpose of this lab is to separate a mixture that contains an acidic, a basic, and a neutral component.

Lab 4: Thin Layer Chromatography

The purpose of this lab was to identify the components of six unknown mixtures using thin layer chromatography and Rf value.

Why is the solubility of a neutral organic compound unaltered by exposure to aqueous acid or base?

The solubility is unaltered when exposed to acids and bases because organic neutral compounds don't interact with them. It does not accept or donate hydrogens, therefore, its solubility stays the same.

Assuming that the separation of a binary mixture in ideal circumstances (concentrated spotting) would be relatively small (less than 0.5 cm), what would be the result of applying too large a spot of this mixture to the TLC plate? How would it affect your ability to distinguish one component from the other on the plate? How would it affect your Rf values? Draw a sample TLC plate to help illustrate your answe

Too large of a spot would result in not being able to see how far the substance moved. Since it only moves 0.5cm it could easily be covered up by a large spot. It could also lead to long streaks and bleeding into surrounding mixtures being tested. If you couldn't see movement you would have an Rf value of 0. If they appeared as streaks, accurate Rf values would not be found.

Ionization

When both the organic acid and organic base in the mixture are ionized, they become part of the aqueous layer.

How will you be visualizing your TLC plates in today's experiment?

With a UV light.