The Grignard reagent, on reaction with acetone, forms :

Options

A. Tertiary alcohol
B. Secondary alcohol
C. Acetic acid
D. Acetaldehyde

Answer

To determine what the Grignard reagent forms when it reacts with acetone, let's break down the reaction step by step.

### Step 1: Identify the Grignard Reagent
The Grignard reagent is represented as R-MgX, where R is an alkyl or aryl group, and X is a halogen (like Cl, Br, or I). This reagent is highly reactive and acts as a nucleophile.

**Hint:** Remember that Grignard reagents are formed by the reaction of an alkyl or aryl halide with magnesium in dry ether.

### Step 2: Identify Acetone
Acetone is a ketone with the structure CH3-CO-CH3. It has a carbonyl group (C=O) flanked by two methyl groups.

**Hint:** Recognize that acetone is a simple ketone and has the formula (CH3)2CO.

### Step 3: Reaction Mechanism
When the Grignard reagent (R-MgX) reacts with acetone, the nucleophilic R group attacks the electrophilic carbon of the carbonyl group (C=O) in acetone. This results in the formation of a tetrahedral intermediate.

**Hint:** The carbonyl carbon is electrophilic and will accept the nucleophile (R group).

### Step 4: Formation of the Intermediate
The attack of the R group on the carbonyl carbon leads to the formation of an intermediate that has an alkoxide structure (R-C(OH)-C(CH3)2). This intermediate contains an oxygen atom with a negative charge.

**Hint:** The intermediate will have a negative charge on the oxygen after the nucleophilic attack.

### Step 5: Protonation of the Intermediate
The next step involves the addition of water (H2O) to the reaction mixture. The alkoxide (R-C(OH)-C(CH3)2) will be protonated by water, resulting in the formation of a tertiary alcohol.

**Hint:** Protonation occurs when the alkoxide ion (O-) picks up a proton (H+) from water.

### Step 6: Final Product
The final product of the reaction is a tertiary alcohol, which has the structure R-C(OH)(CH3)2. This alcohol has three alkyl groups attached to the carbon bearing the hydroxyl (OH) group.

**Hint:** Tertiary alcohols are characterized by having three carbon groups attached to the carbon that holds the hydroxyl group.

### Conclusion
Thus, the Grignard reagent when reacted with acetone forms a tertiary alcohol.

**Final Answer:** Tertiary alcohol.