Grignard Rxn Beyond Labz Notebook PDF

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Download Grignard Rxn Beyond Labz Notebook PDF

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CHM 2021-03 1/11/21

Beyond Labz Virtual Chem Lab Activity- Grignard Reaction Lab Notebook Objective: The purpose of this experiment is to perform a Grignard reaction and familiarize ourselves with the BeyondLabz software. This experiment illustrates the effect of various solvents on a Grignard reaction, which, in this case, synthesizes alcohols to a carbonyl group by Grignard addition. TLC and IR will be used to analyze the product.

COMPOUND

MW (G/MOL)

MP (C)

BP (C)

D (G/CM3)

BENZALDEHYDE

106.12

-26

178-179

1.045

ETHYL MAGNESIUM BROMIDE

133.27

n/a

n/a

1.020

WATER

18.02

0.0

100

1.000

ETHYL ALCOHOL

46.07

-144

78.29

0.79

DIETHYL ETHER

74.12

-116

34.6

0.71

1-PHENYL-1PROPANOL

136.19

n/a

103

0.994

SAFETY CONSIDERATIONS Flammable, acute toxicity (oral and inhalation), eye irritation, respiratory system organ toxicity, and acute aquatic hazard Flammable, acute oral toxicity, skin corrosion, serious eye damage, central nervous system organ toxicity n/a Highly flammable, eye irritation

Flammable, acute oral toxicity, central nervous system oral toxicity Combustible liquid, harmful if swallowed

Procedure: Part 1: Water as the solvent.  Open up Microsoft Word and Beyond Labz. Click “Virtual Chem Lab- Organic” then select “Synthesis” then “Grignard Addition”.  Add the aldehyde substrate- benzaldehyde. It is assumed that 2.50 mL was added.  Add the Grignard reagent- ethyl magnesium bromide. It is assumed that a slight excess of Grignard reagent was added.  Add the solvent- water*. It is assumed that about 15 mL was added.  Confirm the contents of the flask then secure it to the ring stand. 1

     

Double-click on the nitrogen line to add it to the top of the flask. Collect initial TLC (starting time= 0 mins) by double clicking on the TLC chamber and dragging it to the flask. Take a screenshot and paste into Word Doc along with what it means. Start the reaction but clicking the stirring knob on the hot plate (right knob) Advance the clock by one minute until the Grignard reagent has been consumed and record the time. Collect final TLC. Take a screenshot and paste into Word Doc along with what it means. Click on the waste container to discard all materials and reset the synthesis lab.

*Water is the solvent in this reaction only. This will change if the part 1 procedure is utilized in another step. Part 2: Ethanol as the solvent.  Repeat the part 1 procedure but utilize ethanol as the solvent instead of water. Assume about 10 mL was added. Part 3: Diethyl ether as the solvent.  Repeat the part 1 procedure but utilize diethyl ether as the solvent instead of water. Assume that about 10 mL was added. o Instead of advancing the clock one minute at a time until the Grignard reagent has been consumed, advance the clock by 10 minutes at a time until the reaction is consumed. Record the contents of the flask.  Stop the reaction by double-clicking the separatory funnel to move it to the flask.  Double click on the aqueous hydrochloric acid solution to add it to the separatory funnel to protonate the alkoxide and form the alcohol product.  There will now be 2 layers of liquid in the funnel. The organic, less dense later will float on top of the aqueous layer. Remove the aqueous layer by dragging it from the separatory funnel into the red waste container. The organic later will now be in the round-bottom flask.  Drag the ether layer to the cork ring support.  Record the IR spectrum of the product by clicking on the IR spectrometer and dragging the salt plate icon to the flask. Enter your name and date into the “Common Name” field and the name of the compound in the “IUPAC Name” field. Take a screenshot and record it in the Word Doc along with notes of what it represents.  Create a page for this Beyond Labz activity and Insert a File Printout of the Word Doc with the notes and images of the TLC plates and IR spectrum in the class notebook for lab. Observations: Part 1: Water as the solvent. Initial TLC:

The total reaction time for this reaction with water as the solvent in this initial TLC plate is 0 minutes. The lane on the left represents the starting materials and the lane on the right represents what was in the flask at the time that the TLC was measured. The lanes are identical because the reaction has not yet begun, therefore, the starting material is the same thing as what is in the flask and they have the same chemical components and, as a result, the same polarity.

Final TLC:

The total reaction time for this reaction with water as the solvent in this final TLC plate is 1 minute. The lane on the left represents the starting materials and the lane on the right represents what was in the flask at the time that the TLC was measured. Although the Grignard reagent was consumed, there is no change in the TLC plate because the Grignard reaction does not occur in water and, as a result, the polarity is the same. Water is a polar protic solvent and because Grignard reagents are very good nucleophiles, it is not the best option for Grignard reactions because the water protonates and destroys the Grignard reagent.

Part 2: Ethanol as the solvent. Initial TLC:

The total reaction time for this reaction with ethanol as the solvent in this initial TLC plate is 0 minutes. The lane on the left represents the starting materials and the lane on the right represents what was in the flask at the time that the TLC was measured. The

lanes are identical because the reaction has not yet begun, therefore, the starting material is the same thing as what is in the flask and they have the same chemical components and, as a result, the same polarity.

Final TLC:

The total reaction time for this reaction with ethanol as the solvent in this final TLC plate is 1 minute. The lane on the left represents the starting materials and the lane on the right represents what was in the flask at the time that the TLC was measured. Although the Grignard reagent was consumed, there is no change in the TLC plate because the Grignard reaction does not occur in ethanol and, as a result, the polarity is the same. Ethanol is a polar protic solvent and because Grignard reagents are very good nucleophile, it is not the best option for Grignard reactions because the ethanol protonates and destroys the Grignard reagent.

Part 3: Diethyl ether as the solvent. Initial TLC:

The total reaction time for this reaction with diethyl ether as the solvent in this initial TLC plate is 0 minutes. The lane on the left represents the starting materials and the lane on the right represents

what was in the flask at the time that the TLC was measured. The lanes are identical because the reaction has not yet begun, therefore, the starting material is the same thing as what is in the flask and they have the same chemical components and, as a result, the same polarity.

Final TLC:

The total reaction time for this reaction with diethyl ether as the solvent in this final TLC plate is 21 minutes. The lane on the left represents the starting materials and the lane on the right represents what was in the flask at the time the TLC was measured. The TLC reagent was consumed, and a Grignard reaction did occur, and as a result, the right lane is more polar than the starting materials since it is lower on the plate. Diethyl ether is an aprotic solvent and is a great option for Grignard reactions because the Grignard reagent is able to stay intact because there are no acidic hydrogens that could cause protonation.

IR of 1-Phenyl-1-propanol

This IR spectrum of 1-Phenyl-1-propanol represents the functional groups of the molecule when observing signals between 4500 and 1500 cm-1. The signals below 1500 cm-1 are in a region called “the fingerprint region” and have no diagnostic value. The strong, broad, and round signal at about 3800 to 3200 cm-1 indicate an alcohol group. Also, the strong and sharp 5

signals above and below 3000 cm-1 indicate sp2 and sp3 hybridized carbons which portray that there are alkanes and alkenes in the molecule. The weak signals from about 1600 to 2000 cm-1 that are referred to as “overtones” indicate the presence on an aromatic ring. Conclusion: Grignard reactions do not work in protic solvents, like water and ethanol, due to the fact that the solvent protonates and destroys the Grignard reagent. The TLC plates in part 1 and 2 of the procedure indicated that although the Grignard reagent was no longer in the flask, the reaction did not occur and there was not a change in polarity. The reaction works when an aprotic solvent, like diethyl ether, is utilized. The TLC plate and the IR spectrum from part 3 of the procedure proved that the Grignard reaction with diethyl ether as the solvent produced the expected product, 1-Phenyl-1-propanol, with the correct functional groups and produced a change in polarity, making the solution more polar.

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