Reaction Overview:
- Acetyl bromide reacts with excess CH3MgI (Grignard reagent) to form a ketone intermediate.
- The ketone intermediate is then treated with a saturated solution of NH4Cl to give 2-methyl-2-propanol.

Reaction Steps:

Step 1: Formation of Grignard reagent
- CH3MgI is prepared by reacting methyl iodide (CH3I) with magnesium (Mg).
- The reaction occurs as follows:
CH3I + Mg → CH3MgI

Step 2: Reaction of Acetyl bromide with CH3MgI
- Acetyl bromide (CH3COBr) reacts with the Grignard reagent (CH3MgI) to form a ketone intermediate.
- The reaction occurs as follows:
CH3COBr + CH3MgI → CH3COCH3

Step 3: Treatment with NH4Cl
- The ketone intermediate (CH3COCH3) is treated with a saturated solution of NH4Cl to give 2-methyl-2-propanol.
- The reaction occurs as follows:
CH3COCH3 + NH4Cl → (CH3)3COH

Explanation:
- Acetyl bromide (CH3COBr) reacts with the Grignard reagent (CH3MgI) to form a ketone intermediate, acetone (CH3COCH3).
- The reaction between acetyl bromide and the Grignard reagent is a nucleophilic addition reaction. The nucleophilic carbon of the Grignard reagent attacks the electrophilic carbonyl carbon of acetyl bromide. This leads to the formation of a tetrahedral intermediate, which subsequently collapses to form the ketone.
- The ketone intermediate, acetone, is then treated with a saturated solution of NH4Cl. This treatment results in the formation of 2-methyl-2-propanol ((CH3)3COH) through a reduction reaction.
- The saturated solution of NH4Cl serves as a source of H+ ions, which act as a reducing agent in the reaction. The H+ ions react with the carbonyl oxygen of the ketone, causing it to be reduced to a hydroxyl group (-OH). This results in the formation of 2-methyl-2-propanol.
- The final product, 2-methyl-2-propanol, is a tertiary alcohol with a branched structure.

Conclusion:
- The reaction of acetyl bromide with excess CH3MgI followed by treatment with a saturated solution of NH4Cl leads to the formation of 2-methyl-2-propanol.
- This reaction demonstrates the use of Grignard reagents and reduction reactions in organic synthesis.