High School

Remove the solvent using the square-tip Pasteur pipette filtration method. Rinse the crystals with approximately 0.5 mL of ice-cold water and remove the rinse with the Pasteur pipette. Scrape the wet crystals onto a piece of filter paper and allow them to dry before determining the weight and melting point.

Before leaving the laboratory, record your partner's results in your laboratory notebook. Put your product in an appropriate container. Neutralize the filtrate with 1 N sulfuric acid to destroy any remaining reducing agent. Put the aqueous filtrate in the appropriate liquid waste container. Dispose of all contaminated Pasteur pipettes, melting point and TLC capillaries, and TLC plates in the container for chemically contaminated laboratory debris.

**Chemical Safety Note:** Sulfuric acid is corrosive. If any solution containing sulfuric acid comes in contact with your skin, flush the affected area immediately with water for at least five minutes and have another student notify the instructor immediately.

1. Discuss the fact that there is more than one possible stereoisomeric product from the reduction of (±)-benzoin.
2. Discuss the reduction of benzil and identify the products that are possible from this reaction.
3. Based on your and your partner's results, which product(s) was formed? If one product appeared to be favored, speculate as to why this was the case.
4. Why did you need to make two mixed melting point determinations? Did these help you identify the major product? If so, explain how.
5. Discuss and explain the similarities and differences between the reactions run in 2-propanol, methanol, and 95% ethanol.

Answer :

Rinse the crystals with approximately 0.5 mL of ice-cold water and remove the rinse with the Pasteur pipette.

What are the major steps should be taken before leaving the laboratory?

Before leaving the laboratory, also record your partner's results in your laboratory notebook. Put your product in an appropriate container Neutralize the filtrate with 1 N your sulfuric acid to destroy any remaining reducing agent.

Put the aqueous filtrate in the appropriate liquid waste container. Dispose of all contaminated Pasteur pipettes melting point and TLC capillaries, and TLC plates in the container for chemically contaminated laboratory debris.

Therefore, Rinse the crystals with approximately 0.5 mL of ice-cold water and remove the rinse with the Pasteur pipette.

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Final answer:

The reduction of benzoin leads to different stereoisomeric products, with the experiment illustrating the importance of solvent volume in crystallization efficiency. Identification of the major product involves melting point analysis, while the choice of solvent affects the reaction outcomes significantly.

Explanation:

The reduction of benzoin to form different possible stereoisomeric products is a crucial concept in organic chemistry, especially when considering the reactivity and purification process involved. One significant aspect of this process involves the use of the minimum amount of hot solvent for crystallization, as demonstrated through the crystallization of benzil from hot ethanol. It was observed that using the minimum amount of solvent yielded a higher recovery rate compared to using an excess. This illustrates the importance of solvent volume in the crystallization process.

In addition to the practical steps taken in the laboratory for the purification and analysis of the products formed from benzoin reduction, the reaction's stereoisomeric nature raises discussions about the various possible products. Typically, the reduction of benzoin could lead to different stereoisomers, each with unique properties and reactivities. Identifying the major product formed in the reaction requires analyzing the melting point and possibly using mixed melting point determinations to characterize the purity and identity of the stereoisomeric products.

Moreover, the choice of solvent (2-propanol, methanol, and 95% ethanol) also plays a significant role in the reaction outcomes. Different solvents can influence the reaction path, the yield, and the purity of the products formed. This ties back to the general principle in organic synthesis that the conditions, including the choice of solvent and the control of the amount used, are pivotal in steering the reaction towards the desired product.

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