ORGO 2 LAB 5 - Lab for. Chem 2313 PDF

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Lab for. Chem 2313...

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Leigh Burgess Nathalie Myrthil Date of Lab: 10 March 2020 Date of Lab Report: 17 March 2020 Wittig Reaction

OBJECTIVE The objective of this experiment was to synthesize trans-9-(2-phenylethenyl)anthracene from benzyltriphenylphosphonium and 9-anthraldehyde. The purpose of this experiment was to observe an experiment that contains a Wittig reagent as the intermediary step in the reaction. Upon the addition of sodium hydroxide, calcium chloride, and water, students were able to observe that step. With the spotting of the TLC plate at the end of the experiment, students learned about the mechanisms behind the experiment focusing on polarity. REACTION EQUATIONS

Name

Benzyltriphenylphospho nium chloride

Formula

Molar Mass

Density

Melting Point

Solubility in water

388.9 g/mol

1.18 g/cm³

337 °C

Soluble

206.24 g/mol

1.21 g/cm³

103-105 °C 

Insoluble

39.9971 g/mol

2.13 g/cm³

323 °C

418 g/L at 0 °C

84.93 g/mol

1.33 g/ cm³

-142.1 ° C

25.6 g/L at 15 °C

60.09 g/mol

0.803 g/mL

-126 ° C

Miscible

9-anthraldehyde

Sodium hydroxide

Dichloromethane

1- Propanol

THEORETICAL YIELD There is no theoretical yield in this experiment because there is no limiting reagent. PROCEDURE 0.200 g of benzyltriphenylphosphonium chloride, 0.115g of 9-anthraldehyde, and 0.6mL of dichloromethane were added to a test tube. Drops of sodium hydroxide were added to the vial dropwise to the test tube. The mixture is stirred after the addition of each drop. Once all the drops are added, the mixture is stirred for 10 minutes. After the 10 minutes is up, 1.5 mL of water and 1.5 mL of dichloromethane are added to the mixture

and the solution is stirred again. A Pasteur pipette is used to pipette out the bottom layer and is added to a 20mL beaker. The process was repeated again with 1 mL of dichloromethane and the extracted portion was also combined to the 20mL beaker from the previous step. The dichloromethane solution was then dried with calcium chloride. The dichloromethane without the calcium chloride pellets was then added to a round bottom flask and the dichloromethane was evaporated off using a rotary evaporator. The product was then recrystallized with 3 mL of 1-propanol being added to the round bottom flask and heated in the hot water bath until the solid dissolved. The hot solution was then added to a 50 mL beaker and allowed to cool to room temperature. Once cooled to room temperature it was cooled using an ice bath. The solid product was collected using vacuum filtration on a Hirsch funnel. The product was then weighed on the balance and the percent yield was calculated. A TLC plate was spotted using the product, benzyltriphenylphosphonium, and 9-anthraldehyde. 9:1 hexane/ethyl acetate was the developing solvent. Once complete, the Rf value was calculated and the TLC plate was drawn in the lab notebook. The melting point of the product was then determined. OBSERVATION It was noted that once the 0.200 g of benzyltriphenylphosphonium chloride, 0.115g of 9-anthraldehyde, and 0.6mL of dichloromethane were added to a test tube and the drops of sodium hydroxide were mixed in the mixture turned a dark brown, the tube heated up slightly, and the difference between the two layers became apparent. When

the DCM and water were added to the mixture, two distinct layers formed and the organic layer became a more yellowish color. The solution became a yellowish color and was transferred to the rotary evaporator. When the product was then recrystallized, golden colored crystals were noted in the solution. On the TLC plate, it was noted that there were some impurities in the same shown in the extra dot over benzyltriphenylphosphonium and the skewed dot over 9-anthraldehyde. This is thought to be due to the shaking of the TLC container during developing. Deviations in the experiment from the expected values are due to human error and some product was lost in transfer from one vial to another throughout the experiment. CHARACTERIZATION The final product was a tan powdered substance and weighed 1.006 g. The mass of the filter paper was 0.909g. The final melting point was determined to be 135.4 degrees C. Mass of Product= 0.097g Percent Yield= 67.36% Percent Yield Calculation: 0.200 g of benzyltriphenylphosphonium chloride x 1 mol/388.9 g= 0.00051427 mol 0.115g of 9-anthraldehyde x 1mol/206.24 g= 0.0005576 mol 0.00051427 mol x 280.4  g/mol= 0.144g

(0.097g/0.144g) x100= 67.36% TLC Plate=

Rf Values: Product= 3.1/5.15= 0.6019 Benzyltriphenylphosphonium= 0 9-anthraldehyde= 1.5/5.15= 0.2913 CONCLUSION The experiment provided students with the opportunity to observe a reaction that contained a Wittig reagent. The process to synthesize trans-9-(2-phenylethenyl)anthracene from benzyltriphenylphosphonium and 9-anthraldehyde was a multi step reaction that involved pulling skills and knowledge from a variety of different labs and sources. The product was a yellow solid weighing 0.097g. It’s melting point was determined to be 135.4 C. Once the TLC plate was done and had developed, we could see that there was some impurity in our product. This is

most likely due to poor separation of product during vacuum filtration and extraction using the Pasteur pipette. The TLC demonstrated the principle of how our more nonpolar would move with the nonpolar solvent we used. The

benzyltriphenylphosphonium did not move because it is a polar substance....