Session 1: In this lab, we will achieve a simple Friedel-Crafts alkylation of anthracene. The choice of anthracene as an aromatic substrate stems from two considerations. First, there is a question of regioselectivity. Second, anthracene and its derivatives are highly visible under UV light. Session 2: In this lab, we will complete a partial conversion of 9-acetylanthracene using m-chloroperoxybenzoic acid (mCPBA). We will also determine by NMR, the regiochemistry of the reaction. B. Chemical Properties: cetyl chloride CAS #75-36-5 Appearance: colourless to light yellow liquid with a pungent and choking odour Melting point: -112 C Boiling point: 51 C Vapour density: 2.
7 Vapour pressure: 315 mbar at 20 C Density (g cm-3): 1. 104 Flash point: 4 C (closed cup) Explosion limits: 7. 3% – 19% Autoignition temperature: 390 C Water solubility: decomposes aluminum chloride CAS #7446-70-0 Physical State: Crystalline powder Color: yellow – fine Odor: acrid odor – strong odor pH: Not available Vapor Pressure: 0. 004 mbar @ 50 deg C Vapor Density: Not available
Evaporation Rate: Not available Viscosity: Not available Boiling Point: Not available Freezing/Melting Point: 194 deg C ( 381.
20F) Decomposition Temperature: Not available Solubility in water: Reacts Specific Gravity/Density: 2. 440 Molecular Formula: AlCl3 Molecular Weight: 133. 34 anthracene CAS #120-12-7 Appearance: off-white to pale green crystals Melting point: 215 – 219 C Boiling point: 340 C Specific gravity: 1. 25 Vapour pressure: Flash point: 121 C (closed cup) Explosion limits: 0. 6% (lower) Autoignition temperature: nhydrous calcium chloride CAS #10043-52-4 Appearance: white beads or powder Melting point: 782 C Boiling point: Vapour density: Vapour pressure: negligible Specific gravity: 2. 15 Flash point: Explosion limits: Autoignition temperature: anhydrous chloroform (no stabilizer) CAS #67-66-3 Appearance: clear colourless liquid with a sweet odour Melting point: -63 C Boiling point: 61 C Vapour density: 4. 1 Vapour pressure: 159 mm Hg at 20 C Specific gravity: 1. 48 g cm3 Flash point: none Explosion limits: Autoignition temperature: Water solubility: 8 g/l at 20 C
Refractive index: 1. 4459 at 20 C, 589 nm concentrated hydrochloric acid CAS #7647-01-0 Appearance: clear colourless or slightly yellow liquid with pungent odour. Concentrated acid is fuming. Melting point: -25 C Boiling point: 109 C Specific gravity: 1. 19 Vapour pressure: Flash point: Explosion limits: Autoignition temperature: anhydrous magnesium sulfate CAS #7487-88-9 Appearance: solid Melting point: Boiling point: Vapour density: Vapour pressure: Density (g cm-3): 1. 07 Flash point: Explosion limits: Autoignition temperature:
Water solubility: saturated sodium bicarbonate CAS #144-55-8 Appearance: white powder or crystals Melting point: 50 C Boiling point: Vapour density: Vapour pressure: Density (g cm-3): 2. 16 Flash point: Explosion limits: Autoignition temperature: Water solubility: C. Chemical Reaction: Session 1 Session 2 D. Data and Result Look at appendix E. Discussion and Conclusion Session 1 (Partner up for this lab): We assembled a drying tube. Into a clean dry 50 mL round-bottom flask, we added 2. 0 g of anthracene and 15 mL of anhydrous chloroform.
We made an ice-water bath in a beaker that will hold the 50 mL round-bottom flask and placed the ice-water bath on a stir plate in the hood. We had to do the following things as quickly as possible: weighing approximately 3 g of aluminum chloride and adding it to the 50 mL round-bottom flask, also placing a septum securely over the neck of the round-bottom flask and plunge the needle of the drying tube into the septum. We clamped the round-bottom flask in the ice-water bath that we put in the hood. We placed a disposable needle on a 10 mL plastic syringe and used it to take up 4. mL of acetyl chloride. We stuck the acetyl chloride syringe through the septum on the flask and added the acetyl chloride slowly while stirring so that the reaction does not heat up too much –probably over the course of about 20 minutes. Later the acetyl chloride syringe was removed from the septum and allowed the reaction to stir for approximately 20 more minutes in the ice bath. We rinsed the 10 mL syringe with water and collect the water for neutralization with sodium bicarbonate, where we collected most aqueous solutions together for neutralization until the end of the lab. We placed a 1? olygon stir bar in the beaker with the ice and reaction mixture and began stirring. Later slowly added concentrated hydrochloric acid until the white precipitate clears and we had a translucent solution. We poured the contents of the beaker into a 125 mL separatory funnel. We drained off the chloroform layer into a clean 125 mL Erlenmeyer flask. We extracted two times with 15 mL aliquots of chloroform, draining the chloroform layers into the 125 mL Erlenmeyer. We retained about 0. 5 mL of this mixture in a small test tube for TLC. Add the chloroform solution back into the separatory funnel.
Slowly add 20 mL of saturated sodium bicarbonate solution to the separatory funnel. The reaction will produce carbon dioxide gas, so add the sodium bicarbonate slowly. With the stopper off,we swirled the separatory funnel. Then cap it and shake lightly. We drain the chloroform layer into the original Erlenmeyer and added the aqueous solution slowly to the solutions to be neutralized. Bubbles were form when adding to the acetyl chloride rinses previous collected. We continue to wash with 20 mL aliquots of sodium bicarbonate as above until the solution does not evolve carbon dioxide gas..
The solution was fully neutralized when the addition of solid sodium bicarbonate no longer results in the formation of bubbles. We added enough anhydrous magnesium sulfate to dry the chloroform solution in the 125 mL Erlenmeyer. We filtered the solution using a Buchner funnel and filter paper into a 125 mL filter flask. Place the magnesium sulfate in the “Used Magnesium Sulfate” container and toss the filter paper. I took the filtrate to rotavap and ran an NMR, while my partner ran a TLC. Session 2 For second session, we weighed 0. 5 g of 9-acetylanthracene into a 50 mL round-bottom flask.
We saved the remaining 9-acetylanthracene for TLC and added 15 mL of chloroform to the round-bottom flask. Additionally, we added 2. 6 g of 3-chloroperbenzoic acid (mCPBA) to the chloroform solution. We placed the round-bottom flask in a clamp above a stir plate and begin stirring gently for 1 hour at room temperature. We placed the reaction in a 125 mL separatory funnel. We extracted the reaction 5 times with 20 mL aliquots of 1 M sodium hydroxide. We use a 25 mL Erlenmeyer flask to collect the chloroform layer each time and a 125 mL Erlenmeyer flask to collect the aqueous washes.
We dried the chloroform layer with sodium sulfate anhydrous and filter the chloroform solution using a Buchner funnel and filter paper into a 125 mL filter flask. We reserve about ? mL of the chloroform solution in a small test tube for a TLC, while one partner takes the filtrate to rotavap and ran an NMR. F. Questions: Session I: 1. ) Download and print a spectrum of anthracene from www. sigma-aldrich. com. Label the peaks in the spectrum of your product that are due to your product? 2. ) What was the gas evolved when you extracted the reaction mixture with saturated sodium bicarbonate?
The gas evolved when we extracted the reaction mixture with saturated sodium bicarbonate was Carbon di oxide. 3. ) What product would you expect if the reaction got too warm? If the product is warm then we would be expecting acetylantracene and HCl as the product since the acid base reaction leads to exothermic reaction. 4. ) How many equivalents of AlCl3 did you use? Explain why in terms of the mechanism for this reaction? We used 3. 001 grams of AlCl3. As the following mechanism indicates, Friedel-Crafts acylation involves the formation of an acylium ion as the active electrophilic species.
The reactive acylium ion is generated from an acyl halide or anhydride. Aluminum chloride is commonly used for this purpose. Although AlCl3 could potentially affect the catalysis of the Friedel-Crafts acylation reaction, the product, a ketone, is sufficiently basic enough to interact strongly with AlCl3 such that more than one equivalent of AlCl3 is required. The AlCl3 is removed in the aqueous workup step by hydrolysis to HCl and aluminum hydroxide. 5. ) Would the resonance for the methyl group on the acetyl moiety be more downfield or upfield on the NMR spectrum in the diacylated product versus the monoacylated product?
The resultant calculated shifts for the assigned resonances were in good agreement with the observed shifts, the shifts of the CH3 groups near the EF site were then calculated from their geometry in this axis system and the best fit Al and A2. The choice of axis system was then rejected if it did not meet the criterion of having only two methyl groups shifted more downfield than 10 ppm, and no methyl resonance shifted more upfield than -5 ppm. Session II: 1. ) Draw a representation of your TLC from this reaction. Label each spot. 2. ) Write the mechanism for the Baeyer-Villiger reaction.
What are the products of the reaction you performed? 3. ) What do you think the purpose of the sodium hydroxide washes is? The sodium hydroxide is used to improve the percent yield, as well as, to remove sulfurous impurities in a process known as caustic washing. As above, sodium hydroxide reacts with weak acids such as hydrogen sulfide and mercaptans to give the non-volatile sodium salts which can be removed. 4. ) Why is the chloroform layer the bottom layer when performing extractions? Chloroform has a density of 1. 48 g/mL, so the chloroform will be the bottom layer. 5. Which group migrated in the Baeyer-Villiger reaction, methyl or anthracenyl? Using arguments based on your NMR spectrum, explain your answer. Migratory aptitude: H > tertiary alkyl > cyclohexyl > secondary alkyl, aryl > primary alkyl > methyl, and the migrating group is usually the one that can best stabilize positive charge. Thus, anthracenyl group would be migrated in the Baeyer Villiger reaction. G. Reference: List reference you looked up such as the ones for physical and chemical properties fishersci. com sigmaaldrich. com ucm crops wwwchem. csustan. edu H. Appendix:
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