Acetyl bromide reacts with excess of \(\mathrm{CH}_{3} \mathrm{MgI}\) followed by treatment with a saturated solution of \(\mathrm{NH}_{4} \mathrm{Cl}\) gives (a) Acetone (b) Acetamide (c) 2 -methyl-2-propanol (d) Acetyl iodide

Acyl halides, such as acetyl bromide, are known for their high reactivity due to the presence of a good leaving group, the halide ion. This characteristic makes them excellent acylating agents in organic synthesis.

In the context of the exercise, the acyl halide (acetyl bromide) is attacked by the Grignard reagent, which is a nucleophilic carbon species. The bromide ion leaves, yielding a ketone as the initial product. This transformation is a typical example of an acyl halide undergoing a nucleophilic acyl substitution. The nucleophile, in this case, comes from the organometallic compound.

As a tip for students, remember that acyl halides are less stable than other carboxylic acid derivatives; therefore, they can react with a wider range of nucleophiles, including weaker ones.

The nucleophilic addition mechanism characterizes many reactions in organic chemistry involving carbonyl compounds. A nucleophile, which is an electron-rich species, donates a pair of electrons to an electrophilic, electron-deficient carbon atom of the carbonyl group.

This type of reaction expands to many different nucleophiles and electrophiles, but fundamentally, it involves the nucleophile attacking the carbon and forming a new bond. Subsequent steps depend on the nature of the reagents and the workup of the reaction.

In our exercise, the methyl group from the Grignard reagent acts as the nucleophile and adds to the electrophilic carbonyl carbon of acetyl bromide. Students should pay attention to how the polarity of the carbonyl group makes the carbon an electrophile and visualize how the nucleophile adds to this site.

Organometallic reagents are compounds that contain a direct bond between a carbon atom of an organic moiety and a metal. Methylmagnesium iodide, the Grignard reagent used in our exercise, is a prime example. These reagents are highly nucleophilic due to the polarization of the carbon-metal bond.

Grignard reagents are pivotal in forming carbon-carbon bonds in organic synthesis. To harness their full potential, it's crucial to remember that they are incompatible with water or other protic solvents, as they will be readily quenched, resulting in the loss of their reactivity. In the presence of acyl halides, they deliver the alkyl group to the electrophilic center creating new ketones or alcohols after suitable work-ups.

The synthesis of carbonyl compounds, particularly ketones and aldehydes, often utilizes organometallic reagents like Grignard reagents. The carbonyl group's double bond oxygen is highly electrophilic, making it a perfect target for nucleophilic attack.

In this exercise, the synthesis of a carbonyl compound, acetone, from acetyl bromide and a Grignard reagent, is a textbook example of such a transformation. It's essential to be aware that the choice of reagents, solvents, and workup conditions can significantly influence the outcome of the carbonyl compound formed.

A saturated solution of ammonium chloride finishes the reaction by providing a proton to any remaining anionic species, effectively quenching the reaction and stabilizing the product, acetone in this case.