Question

Identify 1 and 2 in the following reaction:

• A.
• B. CH₃MgBr and CH₃CHO
• C.
• D. CH₄ and CH₃CHO
• E.

Answer 1

The Correct Option is C

Reaction Steps:

Formation of Grignard Reagent (Compound 1): The reaction of methyl bromide (CH3Br) with magnesium (Mg) in dry ether forms a Grignard reagent. A Grignard reagent has the general formula R-MgX, where R is an alkyl or aryl group and X is a halogen. In this case, R is methyl (CH3) and X is bromine (Br). So compound 1 is methylmagnesium bromide (CH3MgBr).

Grignard Reaction with a Ketone followed by Acid Workup (Compound 2): The Grignard reagent (CH3MgBr) acts as a strong nucleophile and attacks the carbonyl carbon of the ketone. This forms a new C-C bond. The subsequent acid workup (H3O+) protonates the alkoxide intermediate, resulting in an alcohol.

The ketone structure present will have two methyl groups on one side of the carbonyl, so it will become a 2 degree alcohol after being reacted with the Grignard and then protonated.

Therefore, the correct answer is (C) CH3MgBr and

Answer 2

1. Reaction analysis:

The given reaction involves the formation of a Grignard reagent and its subsequent reaction with an aldehyde. Let us analyze the steps in detail:

2. Step 1: Formation of the Grignard reagent (I):

• Methyl bromide (\( \text{CH}_3\text{Br} \)) reacts with magnesium (\( \text{Mg} \)) in the presence of dry ether.
• This forms the Grignard reagent, \( \text{CH}_3\text{MgBr} \).

3. Step 2: Reaction of the Grignard reagent with an aldehyde:

• The Grignard reagent (\( \text{CH}_3\text{MgBr} \)) reacts with acetaldehyde (\( \text{CH}_3\text{CHO} \)).
• Grignard reagents are strong nucleophiles and react with carbonyl compounds to form alkoxides. The reaction proceeds as follows:
• \[ \text{CH}_3\text{MgBr} + \text{CH}_3\text{CHO} \rightarrow \text{CH}_3\text{C(O)-O-CH}_3 + \text{MgBrOH} \]
• After protonation by \( \text{H}_3\text{O}^+ \), the final product is tert-butanol (\( \text{CH}_3\text{C(OH)}(\text{CH}_3)_2 \)).

4. Identifying 1 and 2:

• 1: The Grignard reagent formed in the first step is \( \text{CH}_3\text{MgBr} \).
• 2: The final product after the reaction with the aldehyde and protonation is tert-butanol (\( \text{CH}_3\text{C(OH)}(\text{CH}_3)_2 \)).

5. Matching with the options:

• Option (A): \( \text{H}_3\text{C-CH}_3 \) and \( \text{CH}_3\text{C(OH)}(\text{CH}_3)_2 \)
  • Incorrect. \( \text{H}_3\text{C-CH}_3 \) (ethane) is not involved in the reaction.
• Option (B): \( \text{CH}_3\text{MgBr} \) and \( \text{CH}_3\text{CHO} \)
  • Incorrect. \( \text{CH}_3\text{CHO} \) is the aldehyde used in the reaction, but it is not the final product.
• Option (C): \( \text{CH}_3\text{MgBr} \) and \( \text{CH}_3\text{C(OH)}(\text{CH}_3)_2 \)
  • Correct. \( \text{CH}_3\text{MgBr} \) is the Grignard reagent (1), and \( \text{CH}_3\text{C(OH)}(\text{CH}_3)_2 \) is the final product (2).
• Option (D): \( \text{CH}_4 \) and \( \text{CH}_3\text{CHO} \)
  • Incorrect. Neither methane (\( \text{CH}_4 \)) nor acetaldehyde (\( \text{CH}_3\text{CHO} \)) is the correct final product.
• Option (E): \( \text{H}_3\text{C-CH}_3 \) and \( \text{CH}_3\text{C(OH)}(\text{CH}_3)_2 \)
  • Incorrect. \( \text{H}_3\text{C-CH}_3 \) (ethane) is not involved in the reaction.

6. Final answer:

The correct option is (C).