Lab #9 - Diels Alder PDF

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This is a lab report that I got a 50/100 but hope it helps!...

Description

NAME: Leia de los Santos CHEM 241L SECTION #: 1008 SEMESTER: Fall 2021

DIELS-ALDER REACTION

PURPOSE The purpose of this reaction is to produce the target compound, cis-4-cyclohexene-1,2dicarboxylic anhydride, by using a reflux system. The reagents are 1,3-butadiene and maleic anhydride. The solvent is xylene. The main reaction performed in this lab is a Diels-Alder reaction. After the initial reaction, recrystallization is used to purify the product mixture and the purified product is analyzed by calculating its percent yield and measuring its melting point. PHYSICAL PROPERTIES Compound

Molecular Formula

Molar Mass (g/mol)

Density (g/cm3)

Melting Point (°C)

Boiling Point (°C)

3-Sulfolene (2,5-Dihydrothiophene 1,1-dioxide)

1,3-Butadiene Maleic anhydride

C4H6O2S

118.155

---

64.0(4)

---

C4H6

54.091

0.614925 (p>1 atm)

-108.9(1)

-4.6(2)

C4H2O3

98.057

1.31460

52.56(4)

202

REACTIONS:

 In situ generation of 1,3-butadiene

 Diels-Alder Reaction

PROCEDURE 0.0994 grams of maleic anhydride and 0.2628 grams of 2-sulfolene were added to a 3 mL conical vial with a boiling chip. Both reagents were a white powder. 15 drops of xylene were also added to the conical vial. Xylene was a clear liquid. The conical vial that contained the reagents and solvent was placed on an aluminum block on a hot plate. A condenser was clamped and connected to the conical vial using vacuum grease. Then, a thermometer was clamped and placed onto the aluminum block on the hot plate. Two rubber tubings were attached to the condenser: one connected the inlet to the tap water and the other connected the outlet to the sink. The heat of the hot plate was increased until the mixture began to boil. The mixture began boiling at 135°C. Once it started to boil, the mixture continued to boil for another 20 minutes which acted as the reflux. The conical vial and its contents were cooled down on the lab bench for 20-30 minutes. The color of the mixture within the conical vial was brown and cloudy. The solution was then transferred to a Craig tube where 10 drops of Toluene was added to the mixture. The initial 10 drops of Toluene made the solution too saturated, so an additional 5 drops were added to help the recrystallization process. The Craig tube was placed into a hot water bath until all the solids dissolved. The dissolving process was aided by tapping and swirling the Craig tube occasionally. The hot plate had a temperature of 210°C. After all the solids had successfully dissolved, the Craig tube was removed from the water bath and cooled on the lab bench. By this time, the contents were now a lighter brown color. Once the Craig tube had cooled down, the procedure of Recrystallization was carried out using a Teflon plug and a test tube. The Recrystallization apparatus was centrifuged while an empty watch glass was weighed out, which came out to be 56.2129 grams. The crystals were collected from the Craig tube and weighed using the pre-weighed watch glass. The crystals were air dried for 10 minutes before weighing. The weight of the watch

glass and crystals was 56.252 grams. After the necessary weight of the products were obtained, the percent yield, theoretical yield and actual yield were calculated. Additionally, the melting point of the product obtained was evaluated to be 8295°C. DATA/RESULTS

Reagents

Required # of mmol

Actual mass used (g)

Actual # of mmol

Maleic anhydride

1.0

0.00994

0.09586261

3-sulfolene

2.2

0.260

2.20049934



The mass of the pre-weighed watch glass = 56.2129 grams



The mass of the watch glass + the product = 56.252 grams



The actual yield of the product = 0.0391 grams



The limiting reagent = Maleic Anhydride



The theoretical yield = 0.015 grams



The percent yield = 260.7%



Experimental melting point of the product = 82-95°C ( cis-4-cyclohexane-1,2-dicarboxylic anhydride, lit. m.p. = 102 ˚C)

DISCUSSION & CONCLUSION 0.096 mmol of Maleic Anhydride and 2.200 mmol of 3-Sulfolene were used in this experiment. After weighing the watch glass without the product crystals and then with the product crystals, I calculated that I had recovered 0.0391 grams of the target product. With this, I was able to determine that the limiting reagent in this reaction was Maleic Anhydride as it had the lower theoretical yield of 0.015 grams. I then took the actual yield of the product crystals (0.0391) divided by the theoretical yield and came up with 260.7%. The expected results of this lab included obtaining a cyclohexene derivative while having a high percent yield of the desired product. Additionally, another expected result would be to obtain a pure desired product. Since this lab called for a reaction (i.e., a Diels-Alder reaction), the product that I hoped to produce was cis-4cyclohexene-1,2-dicarboxylic anhydride. However, when analyzing my calculations, I noticed that the literature melting point value of the desired product is 102 °C, but the experimental melting point range of our product was 82-95 °C. Additionally, I was able to calculate the mmol used in this lab by taking the actual grams used multiplied by the compound’s molar mass multiplied by 1000mg/1. From there, I used the calculated mmol multiplied by 10-3 multiplied by the compound’s molar mass. Both calculations were performed on Maleic Anhydride and 3-Sulfolene.

When I had analyzed my percent yield, after calculating the limiting reagent and theoretical yield, I noticed that my experiment percent yield was greater than 100% which is physically impossible. Therefore, I can confidently conclude that I was not able to produce the desired cyclohexene product and it was not pure. A reasonable explanation for this discrepancy could be that my calculations for the limiting reagent, theoretical yield, and percent yield were wrong. But a mistake that could have been made in this experiment would be that I did not allow the crystals to dry for a full 10 minutes, resulting in some of the crystals to still be wet and forcing the weight of the crystals to be much higher than the theoretical yield (which would explain the “greater than 100%” percent yield).

Post-Lab Questions 1. In this experiment, why 3-sulfolene was used instead of 1,3-butadiene? Explain thoroughly for full credit. Our primary reagent, 1,3-butadiene, was produced by the In-situ reaction which entailed 3-sulfolene being broken down into 1,3-butadiene and sulfur dioxide. 3sulfolene was used as a measurement in this experiment because 1,3-butadiene is a gas which would make it harder to measure. Whereas 3-sulfolene (i.e., a solid) is much easier to handle and measure for the calculated results of this experiment. 2. What diene and dienophile would you need to prepare 1-methyl-4propylcyclohexene? In a Diels-Alder reaction, the reaction occurring is a [4+2] pi cycloaddition reaction. The 4 pi electrons come from a diene (electron rich) with two double bonds and the 2 pi electrons come from a dienophile (electron poor) with one double bond. To produce the desired product of 1-methyl-4-propylcyclohexene, the diene would need to be 2,4-octadiene (which would supply the 4 pi electrons) and the dienophile would need to be ethylene (which would supply the 2 pi electrons)....