Aniline on reaction with acetyl chloride gives: (a) Phenol (b) Acetamide (c) Acetanilide (d) Benzene

When studying organic chemistry, one comes across numerous reactions, each with its unique set of reagents and products. In the context of National Eligibility cum Entrance Test (NEET) preparations, understanding these reactions is vital. One such reaction is the interaction between aniline and acetyl chloride.

Aniline, with the scientific formula of C6H5NH2, is a primary amine where the amino group is directly bonded to a phenyl group. Acetyl chloride, denoted by CH3COCl, is characterized by the acyl group attached to a chloride. When these two chemicals react, acetyl chloride acts as an acylating agent, transferring its acetyl group to aniline. The nitrogen atom in aniline is nucleophilic, meaning that it has an affinity for positive charges, making it an ideal candidate for the acyl group to attach. As a result of this reaction, acetanilide is formed, which is an amide. An amide linkage occurs when the acyl group gets bonded to the nitrogen atom of aniline.

In organic chemistry, the acylation reaction mechanism plays a crucial role in the formation of complex molecules. An acylation reaction involves introducing an acyl group into another compound, which in this case, involves the transformation of aniline into acetanilide.

The mechanism for this process begins with the nucleophilic attack of the amine nitrogen of aniline on the carbonyl carbon of the acetyl chloride. This step is followed by the departure of the chloride ion, a good leaving group. The result is the formation of a tetrahedral intermediate, which eventually collapses to give rise to the amide product, acetanilide. The sequence typically involves two main stages:

• Nucleophilic attack and formation of a tetrahedral intermediate.
• Elimination of a leaving group and reformation of the carbonyl, producing the amide.

Understanding this mechanism is important as it underpins a wide variety of transformations in both laboratory and biological chemistry, and it's a key concept for students preparing for exams like NEET.

Identification of organic compounds is an essential skill for students, especially when preparing for competitive exams like NEET. Organic molecules can be characterized by their functional groups, which are specific groups of atoms that impart unique chemical properties to the compound.

In the given exercise, the conversion of aniline to acetanilide can be seen as a transformation of a primary amine to an amide. This change can be detected and confirmed through various analytical techniques such as infrared spectroscopy, which would showcase the presence of the amide bond through specific absorptions. Other methods such as nuclear magnetic resonance (NMR) spectroscopy can unveil details regarding the environment of hydrogen atoms and the carbon framework of the molecule. Besides, qualitative tests, such as the reaction with nitrous acid, can discriminate primary amines from secondary and tertiary amines. For NEET aspirants, mastering the identification of functional groups and understanding the reactions they undergo is essential in solving organic chemistry problems efficiently.