This section contains multiple choice questions. Each question has 4 choices (a), (b), (c) and (d), out of which ONLY ONE is correct. The structure of the product formed when cyclohexanone reacts with dimethylamine in presence of catalytic amount of an acid such as \(\mathrm{p}\) -toluene sulphonic acid is

Understanding the imine formation reaction is key for students studying IIT JEE Organic Chemistry. An imine is a functional group or compound containing a carbon-nitrogen double bond, with the nitrogen atom typically connected to at least one organic substituent.

The process of imine formation involves a carbonyl compound such as an aldehyde or a ketone reacting with an amine. This kind of reaction is typically acid-catalyzed, meaning it requires the presence of an acid to proceed effectively. The general mechanism involves the nucleophilic attack of the amine on the carbonyl carbon, followed by a series of steps that result in the loss of water (dehydration) and formation of a C=N double bond.

Key Steps in the Formation of Imines:

• Addition of the amine to the carbonyl group to form a carbinolamine intermediate.
• Dehydration of the carbinolamine intermediate to form an imine.

In the context of IIT JEE problems, students should be able to recognize the starting materials and the conditions favoring imine formation, anticipate the structure of the imine product, and understand the significance of the acid catalyst in the mechanism.

In organic synthesis, the reaction between cyclohexanone and dimethylamine is a specific example of imine formation. Cyclohexanone, a cyclical ketone, is characterized by a six-membered ring with a carbonyl functional group. When cyclohexanone is treated with dimethylamine, a secondary amine, in the presence of an acid catalyst, they react to form an imine.

During this reaction:

• Cyclohexanone's carbonyl group is attacked by the nitrogen of dimethylamine.
• An intermediate carbinolamine forms initially.
• This intermediate loses water to become a cyclic imine, also known as a Schiff base.

The resulting product is a six-membered ring with a N-(dimethyl)imine group attached to it. Students should be able to visualize this process to understand not just the 'what' of the reaction, but also the 'why' and 'how', which is essential for mastering organic chemistry concepts for the IIT JEE examination.

Acid-catalyzed reactions are common in the realm of organic chemistry, playing a crucial role in facilitating many types of chemical transformations. In the context of imine formation, the role of the acid catalyst is pivotal. A catalytic amount of an acid, such as p-toluene sulphonic acid (p-TsOH), is often used to accelerate the reaction by activating the carbonyl group and assisting in the dehydration step.

In acid-catalyzed imine formations:

• The acid catalyst donates a proton to the oxygen of the carbonyl group, increasing its electrophilicity.
• The increased electrophilicity makes the carbonyl carbon a better target for nucleophilic attack by the amine.
• Additionally, the acid helps in the removal of water during the dehydration step.

The careful control of reaction conditions, particularly the acid catalyst, determines the success of the imine creation. These subtle yet critical aspects of acid-catalyzed reactions are what students should aim to master, as they will encounter them frequently in IIT JEE Organic Chemistry questions.