Question

Chloroethane reacts with magnesium in dry ether to form \(\mathrm{X}\). When \(\mathrm{X}\) is hydrolyzed, a carbon compound \(\mathrm{Y}\) and \(Z\) are formed. Which of the following is \(Y ?\) (a) \(\mathrm{C}_{2} \mathrm{H}_{4}\) (b) \(\mathrm{C}_{2} \mathrm{H}_{2}\) (c) \(\mathrm{C}_{2} \mathrm{H}_{6}\) (d) \(\mathrm{C}_{6} \mathrm{H}_{6}\)

Short answer

The compound \( Y \) is \( \text{C}_2\text{H}_6 \) (option c).

Step-by-step solution

Understanding the Reaction

Chloroethane (C2H5Cl) reacts with magnesium (Mg) in dry ether to form Grignard reagent. The reaction is as follows: \[ \text{C}_2\text{H}_5\text{Cl} + \text{Mg} \xrightarrow{\text{Ether}} \text{C}_2\text{H}_5\text{MgCl} \]This compound \( \text{C}_2\text{H}_5\text{MgCl} \) is known as the Grignard reagent \( X \).

Hydrolysis of Grignard Reagent

When the Grignard reagent \( \text{C}_2\text{H}_5\text{MgCl} \) is hydrolyzed, it reacts with water (H2O) to form an alkane, \( \text{C}_2\text{H}_6 \), and magnesium hydroxide \( \text{Mg(OH)}_x \).The hydrolysis reaction is:\[ \text{C}_2\text{H}_5\text{MgCl} + \text{H}_2\text{O} \rightarrow \text{C}_2\text{H}_6 + \text{Mg(OH)Cl} \]

Identify Compound \( Y \)

After hydrolysis of the Grignard reagent, the compound \( Y \) that is formed is \( \text{C}_2\text{H}_6 \), which is ethane. It corresponds to option (c).

Confirming Answer

The compound \( Y \) produced from the hydrolysis of the Grignard reagent \( \text{C}_2\text{H}_5\text{MgCl} \) is indeed \( \text{C}_2\text{H}_6 \). This confirms that the correct option is (c) \( \text{C}_2\text{H}_6 \).

Key concepts

Grignard Reagent

The Grignard reagent is a significant compound in organic chemistry, providing valuable tools for bond formation. It's generally prepared by the reaction of an alkyl halide with magnesium in the presence of a dry ether solvent. In our case, chloroethane reacts with magnesium to form \(\text{C}_2\text{H}_5\text{MgCl} \), the Grignard reagent. This reaction is important due to the unique properties of Grignard reagents. They are highly reactive and can react with many electrophilic compounds, facilitating the creation of new carbon-carbon bonds.

• The reaction of chloroethane and magnesium occurs smoothly in an anhydrous environment. The presence of water can ruin the reaction by converting the Grignard reagent into magnesium hydroxide before it can be used.
• Grignard reagents such as \(\text{C}_2\text{H}_5\text{MgCl} \) are strong nucleophiles, making them versatile for different reactions.

Overall, the formation of Grignard reagents is foundational for synthetic routes in organic chemistry, given their widespread use in forming various molecules.

Hydrolysis Reaction

Once formed, Grignard reagents can undergo hydrolysis, which is their reaction with water. This process is vital because it leads to the formation of an alkane and a byproduct, generally magnesium hydroxide in some form. In the reaction given:\[\text{C}_2\text{H}_5\text{MgCl} + \text{H}_2\text{O} \rightarrow \text{C}_2\text{H}_6 + \text{Mg(OH)Cl}\]Hydrolysis essentially 'kills' the Grignard reagent by providing a proton, which converts the alkyl group into an alkane. Understanding this reaction is crucial for predicting the products formed when a Grignard reagent interacts with water.

• The hydrolysis of Grignard reagents is specific to the structure of the starting material. For example, \(\text{C}_2\text{H}_5\text{MgCl} \) yields ethane (\(\text{C}_2\text{H}_6\)) when hydrolyzed.
• This reaction is a typical example of how organometallic compounds can lead to the creation of simple hydrocarbons through a straightforward reaction process.

This reaction is fundamental in organic synthesis, often serving as a step to generate specific hydrocarbons.

Chloroethane

Chloroethane (C₂H₅Cl), also known as ethyl chloride, is a haloalkane that plays a role in the formation of Grignard reagents. Its simple structure serves as a starting point for this transformative reaction. Here’s what you need to know about chloroethane:

• Chloroethane is an organic compound that consists of an ethyl group bonded to a chlorine atom.
• It's typically used in industry both as a precursor to other chemical substances and as a refrigerant.
• When chloroethane reacts with magnesium in dry ether, it forms the Grignard reagent \(\text{C}_2\text{H}_5\text{MgCl} \), which opens pathways to numerous synthetic transformations in organic chemistry.

Chloroethane is useful because it readily undergoes nucleophilic substitution reactions due to the presence of the chlorine leaving group, making it incredibly effective in forming Grignard reagents.