In the following sequence of reactions, \(\mathrm{CH}_{3}-\mathrm{CH}\left(\mathrm{NH}_{2}\right)-\mathrm{CH}_{3} \stackrel{\mathrm{HNO}_{2}}{\longrightarrow} \mathrm{A}\) oxidation \(\longrightarrow \mathrm{B} \frac{\text { (i) } \mathrm{CH}_{3} \mathrm{MgI}}{\text { (ii) } \mathrm{H}^{+} / \mathrm{H}_{2} \mathrm{O}} \mathrm{C}\) the compound C formed will be: (a) Butanol-1 (b) 2 -methylpropanol-1 (c) 2 -methylpropanol-2 (d) Butanol-2

Understanding the diazonium salt formation is crucial for students preparing for NEET. This reaction involves the conversion of primary amines into diazonium salts using nitrous acid (HNO_2). Specifically, when a primary amine reacts with HNO_2, it forms a diazonium salt, which typically occurs in cold conditions around 0–5°C. One of the remarkable things about diazonium salts is that they are versatile intermediates in organic synthesis. They can easily be transformed into a variety of functional groups, such as alcohols, halides, or cyanides, and this transformation happens through nucleophilic substitution or reduction processes.

For example, in the provided problem, the primary amine in the initial compound (CH_3-CH(NH_2)-CH_3) is converted into an alcohol, denoted as compound A. This change occurs because the diazonium salt, which forms under the reaction conditions, readily decomposes to release nitrogen and create an alcohol group at the carbon where the amine was attached.

Oxidation reactions play a fundamental role in organic chemistry, particularly in transforming alcohols into ketones or aldehydes. The difference in the oxidation product depends on the type of alcohol undergoing the reaction.

Oxidation of Primary Alcohols

Primary alcohols are typically oxidized to aldehydes and can further oxidize to carboxylic acids.

Oxidation of Secondary Alcohols

Secondary alcohols, on the other hand, are oxidized to ketones, and this reaction generally stops at the ketone stage since further oxidation requires breaking a carbon-carbon bond, which is not favorable under mild conditions.

In our NEET example, the oxidation of propanol-1, a primary alcohol, results in the formation of propanone (acetone), a ketone. It is vital for students to understand the conditions needed for oxidation and the types of reagents used, such as KMnO_4, CrO_3, or PCC(Mild Oxidation for alcohols to aldehyde).

The Grignard reaction is a pivotal transformation in organic chemistry that allows the creation of new carbon-carbon bonds, which is fundamental for synthesizing more complex molecules. This reaction involves the use of Grignard reagents, which are organomagnesium compounds that have the formula R-MgX, where R is an alkyl or aryl group and X is a halogen.

Grignard reagents are highly nucleophilic and react with electrophilic carbon atoms. Specifically, they typically add to carbonyl compounds, such as aldehydes and ketones, to form alcohols after hydrolysis.

Mechanism Overview

The Grignard reagent attacks the electrophilic carbonyl carbon, pushing the pi-bond electrons onto the oxygen. Subsequent hydrolysis (addition of water and an acid) converts the resulting alkoxide into the alcohol.

In our exercise, CH_3MgI, the Grignard reagent attacks the carbonyl carbon in acetone to eventually yield a tertiary alcohol after the hydrolysis step.

The synthesis of tertiary alcohols is of great significance, given their wide use in different chemical industries and pharmaceutical applications. Tertiary alcohols have a carbon atom connected to three alkyl groups and the hydroxyl (-OH) group. They can be synthesized through various reactions, one of the most common being the Grignard reaction.

In the context of the NEET examination, understanding this synthetic route is essential when solving organic chemistry problems. Once the Grignard reagent adds to the ketone, it forms a new carbon-carbon bond, and the subsequent treatment with water and an acid leads to the formation of the tertiary alcohol.

Exam Approach

Students should recognize the structural clues: a tertiary alcohol is formed when a carbonyl compound reacts with an excess of a Grignard reagent, followed by hydrolysis. In the reaction sequence provided, the correct option for compound C is 2-methylpropan-2-ol (c), which exemplifies the creation of a tertiary alcohol from a ketone.