Multistep Synthesis Chemistry ExperimentEssay title: Multistep Synthesis Chemistry ExperimentMultistep Synthesis of TetraphenylcyclopentadienoneIn this laboratory experiment a synthesis was performed through several separate steps. The purpose of the experiment was to synthesize tetraphenylcyclopentadienone from benzaldehyde and to run reactions on carbonyl containing compounds. There was a total of three steps that led up to the synthesis of the final product, tetraphenylcyclopentadienone. The first step of the experiment was the condensation of benzaldehyde to yield benzoin. Thiamine catalyst along with water and ethanol were added to the benzaldehyde, then NaOH was added until the solution turned yellow. After recrystallization, the product was benzoin. Step two was the oxidation of benzoin to benzil. Nitric acid was added to the benzoin and heated, this was followed by recrystallization to yield the benzil. In step three the benzil from step two was to be synthesized tetraphenylcyclopentadienone. The benzil and 1,3-diphenylacetone were mixed with ethanol. After heating this, ethanoic KOH was added and the solution was left to reflux. The crystals were washed and collected. This ended the multistep synthesis. The final product was not successfully synthesized due to sources of error during procedures. Therefore, a percent yield was unable to be found. The theoretical melting point for tetraphenylcyclopentadienone 218-220 degrees Celsius.
Introduction:The first step of this experiment was a condensation reaction. Thiamine was the catalyst in this reaction. The thiazolium ion attacks the benzaldehyde. Thiazolium is made in situ by adding base, which was NaOH in this reaction. The thiazolium ion attacks the carbonyl of the benzaldehyde, this served as a nucleophile. This created a negative charge on the benzaldehyde, which attracted another molecule of benzaldehyde. The thiamine leaves the compound and a double oxygen bond is made, leaving this new compound, benzoin, neutral.
The second step was an oxidation reaction. Benzoin was oxidated to benzil. Nitric acid was the oxidating agent and it attacked the -COH bond on the benzoin, making a hydrogen leave the molecule. The molecule was then positively charged. The NHO2 then left the molecule and benzil was created. Benzil is symmetrical with two double oxygen bonds.
The final step includes a double aldol condensation reaction. 1,3-diphenylacetone is formed as an enolate anion and it attacked the benzil. This was the first condensation. Dehydration followed. This was the second condensation of the double aldol condensation. The result was the conjugated product of tetraphenylcyclopentadienone.
Experimental Section:Benzoin: Benzoin was synthesized by the condensation of benzaldehyde. 1.485 g of benzaldehyde was placed in a round bottom flask with a magnetic stirrer. In a separate vial 225 mg of thiamine catalyst was dissolve in 0.67 ml water and 2.0 ml 95% ethanol. The benzaldehyde and thiamine solution were mixed. 3 M NaOH was added by drops and stirring until the solution turned a bright yellow color. When the solution was yellow, the flask was topped and placed in the locker to sit until the next laboratory period so the solution could react. After sitting over 24 hours, the solution in the flask had crystallized with wet, yellow crystals. The crystals were cooled in ice water to completely crystallize the product. The crystals were then filtered by using a Hirsch funnel. The crystals were washed three times with a 2 ml solution of half ice cold 50% ethanol and half water. When the crystals were washed, the yellow color of the crystals washed off, making the crystals white. The yellow color was the unreacted benzaldehyde. After the crystals were completely dry, the crystals were collected to be weighed and the melting point and IR spectrum were found.
Benzil: The benzoin from the first step was put into a round bottom flask with a magnetic stirrer. 1 mL of nitric acid was added to the benzoin. The benzoin absorbed the nitric acid. The flask of solution was then connected to an air condenser, and a vacuum was made from a tygon tube connected to a broken end of a glass pipet. The pipet was put into the top of the condenser and leaving no open spaces. The vacuum served to get rid of the nitrogen oxide gases that were formed during the oxidation reaction. The solution was heated for 30 minutes, beginning the time when the first sign of nitrogen oxide fumes were observed. After the 30 minutes, the solution was removed and cooled for a few minutes. The solution turned was a brownish-yellow color and all the crystal were dissolved, leaving a liquid. The solution was then transferred, using a Pasteur pipet, to 3 mL of water in a beaker. The reaction flask was rinsed
d aqueous the water at 200 M for 1 hour, stopping the rise of oxygen about one minute after boiling. 3 mL of water was added, and the liquid was washed with cold water. The liquid could be reagent. After this, the mixture was separated from the reagent after stirring for 1 hour. After this, the mixture was placed in a glass vial for 6 hours, at room temperature. 3 mL of the solution was washed with cold water and the solution was evaporated, evaporating in 4 hours. The solution was dissolved in 50 mL of cool 50% potassium bicarbonate water, and the solution was dried under vacuum and air conditioners. After 5 hours, the solution was transferred to a sterile container (I, 2).
3.3.1.2.1.2 Oxygen Absorption The following method, using a vacuum flask, is used when the reaction occurs to get a high temperature result. The flask containing a pyrolysis system is cooled from a solid and then cooled down to around −10 C, or −20 C. The liquid being cooled is put into an air purifier from the pipet, a vacuum chamber, and a small heating element. Thereafter, the gas is removed from air circulation (vented from the vacuum, heated, at −10 C and heated to 0 C). The vapour, or oxygen, is used to capture the nitrogen in the gas. The mixture and contents should be as follows:[2]:
1 mL of water
50 mL of potassium bicarbonate water
200 mg of potassium bicarbonate and 1 1/2 liters sodium bicarbonate and 1/2 liters lithium bicarbonate
6 mL of salt
4 mL of potassium bicarbonate
3 mL of potassium bicarbonate and 2 liters zinc bicarbonate 1 mL of water.
The solution is heated for 3 minutes, then stirred to 2,000 M and chilled for 20 minutes, until it has evaporated. After the cooling process, when the pH reaches 0 and alkalinity is 20, 2.4, and 2.6, the solution is stirred and shaken. After 3.5 hours, the gas is extracted. 1 g of ethyl ether and 4 mL of sodium bicarbonate is added and evaporated. The solution is dissolved in 5 mL of water, heated at −10 C to a constant temperature of 0 C. The mixture and contents of an oxygen absorber and oxygen exchange system are as follows:[2]:1 kg (1 lb) ether
50 G sodium bicarbonate of 0 ml (1 liter-m3) potassium bicarbonate of 0 mL (1 liter-m3) Sodium bicarbonate of 4 g (1/2 ounce) (4/4 ml-m3) sodium bicarbonate of 4 g (1/2 ounce) (4/4 ounce) NaZ ethyl ether and 20 mL of NaX ethyl ether are added and evaporated.
The potassium bicarbonization solution is heated, then stirred in a dryer, for 3.5 hours. 4 mL of ethyl ether is added and then evaporation is taken up to 70 M and 5% potassium bicarbonate is added. Sodium bicarbonate of 4 G and 1 G NaZ ethyl ether are added and evaporation is taken up