Question

Which of the following is not correct about Grignard reagent?

• A. It is a nucleophile
• B. Forms new carbon-carbon bond
• C. Reacts with carbonyl compounds
• D. It is an organomanganese compound

Hint:

Grignard reagents contain magnesium (Mg), not manganese (Mn).

Answer 1

The Correct Option is D

Step 1: Understanding Grignard Reagents
Grignard reagents are organomagnesium compounds of the form \( {R} - {MgX} \).
Step 2: Evaluating the Options
They act as strong nucleophiles.
They react with carbonyl compounds to form alcohols.
They are not organomanganese compounds (which contain Mn instead of Mg).
Thus, the correct answer is (D).

Answer 2

Step 1: Understand what a Grignard reagent is
A Grignard reagent has the general formula RMgX, where:
- R = alkyl or aryl group
- Mg = magnesium
- X = halogen (Cl, Br, or I)
It is an organomagnesium compound, commonly used in organic synthesis for forming carbon-carbon bonds.

Step 2: Preparation of Grignard reagent
Grignard reagents are prepared by reacting an alkyl or aryl halide (R–X) with magnesium metal in dry ether:
R–X + Mg → R–Mg–X
This reaction must be carried out in anhydrous (dry) conditions, as Grignard reagents react vigorously with water.

Step 3: Reactivity of Grignard reagent
Grignard reagents are highly reactive due to the polar carbon-magnesium bond. The carbon is nucleophilic and can attack electrophilic centers like carbonyl groups.
For example:
R–Mg–X + H₂C=O → R–CH₂–OH (a primary alcohol after hydrolysis)

Step 4: Eliminate correct statements
If the options included statements such as:
- “Grignard reagent is reactive with water.” → This is correct.
- “Grignard reagent is used to prepare alcohols.” → This is correct.
- “Grignard reagent is an organomagnesium compound.” → This is correct.

Step 5: Identify the incorrect statement
The statement “It is an organomanganese compound” is incorrect.
Reason: Manganese (Mn) is not involved in Grignard reagents. They are organomagnesium compounds, involving magnesium (Mg) only.

Final Answer:
The incorrect statement is: “It is an organomanganese compound”
This is because it misrepresents the chemical identity of Grignard reagents.