Please help!

It's one of the prelab questions.

**Exp. Ethanol from Sucrose
The diethylacetal of acetaldehyde can be detected by gas chromatography. How does this impurity arise in fermentation?

**Exp. Acetaminophen
In the reaction between p-aminophenol and acetic anhydride to form acetaminophen, 4.5 mL of water were added. What was the purpose of the water?

For the prelab question about the impurity in the production of ethanol from sucrose, the impurity is the diethylacetal of acetaldehyde. This impurity arises in fermentation due to condensation reactions between acetaldehyde and ethanol formed during the process. To understand this, let's break it down step by step:

1. Fermentation: Sucrose is fermented by yeast or bacteria to produce ethanol and carbon dioxide. This process involves breaking down sucrose into glucose and fructose, and then converting these sugars into ethanol.

2. Formation of acetaldehyde: During fermentation, enzymes in the yeast or bacteria convert glucose into pyruvate. Pyruvate is then converted to acetaldehyde, releasing carbon dioxide in the process.

3. Formation of diethylacetal: Acetaldehyde is a highly reactive compound and can react with ethanol when present. The reaction between acetaldehyde and ethanol forms the diethylacetal of acetaldehyde, which is an impurity in the final product.

To prevent the formation of this impurity, it is important to control the fermentation conditions, such as temperature, pH, and oxygen levels. Additionally, separating the impurity through distillation or other purification techniques can help improve the purity of ethanol.

Regarding the purpose of adding water in the reaction between p-aminophenol and acetic anhydride to form acetaminophen, let's understand it as well:

1. Reaction between p-aminophenol and acetic anhydride: Acetaminophen, also known as paracetamol, is synthesized by reacting p-aminophenol with acetic anhydride. This reaction results in the formation of acetaminophen and acetic acid.

2. The role of water: Adding 4.5 mL of water in this reaction serves as a source of hydroxide ions (OH-) that facilitates the reaction. Water can act as a base and promote the hydrolysis of the acetic anhydride. Hydrolysis is the chemical process that involves the breaking of chemical bonds through the addition of water.

When acetic anhydride reacts with water, it forms acetic acid. The hydroxide ions present in water can interact with acetic acid, creating acetate ions. These acetate ions then react with p-aminophenol to produce acetaminophen.

In summary, the water is added in the reaction between p-aminophenol and acetic anhydride to provide hydroxide ions that promote the reaction and facilitate the conversion of acetic anhydride to acetic acid, ultimately leading to the synthesis of acetaminophen.