Question

The incorrect option regarding the following reaction sequence is (A) Reaction is reversible and catalysed by acid (B) \(\mathrm{Z}\) can be alkyl, aryl, \(\mathrm{OH}, \mathrm{NHCONH}_{2}\) (C) Product is favoured because of rapid dehydration of (P) (D) If \(\mathrm{NHZ}_{2}\) is used in place of \(\mathrm{H}_{2} \mathrm{~N}-\mathrm{Z}\), then imine will be obtained as (Q)

Short answer

Upon analyzing all the options, none of them seem to be incorrect based on the limited information given in the exercise. It is possible that an error has been made in the question or the problem requires more context to deduce the incorrect option.

Step-by-step solution

Option (A): Reversible Reaction and Acid Catalysis

We are not given any information about the reaction itself, making it difficult to determine if this statement is true or false. However, we do know that many organic reactions are reversible and catalysts, especially acid catalysts, are used to speed up the reaction. Without any additional information, we cannot conclude that this option is incorrect.

Option (B): Z Substituent Options

The \(\mathrm{Z}\) group refers to a substituent that can be present in the reactant or product molecule. The given options for \(\mathrm{Z}\) are alkyl, aryl, \(\mathrm{OH}, \mathrm{NHCONH}_{2}\). All of these are viable substituents in organic reactions. Therefore, this statement is reasonable and does not seem to be incorrect.

Option (C): Product Favored by Rapid Dehydration of (P)

Without any information on the reaction sequence or the structure of the reactants and products, we cannot determine if this statement is true or false. However, it is possible for a product to be favored in a reaction because of rapid dehydration of an intermediate, leading to thermodynamic control of the reaction. We cannot conclude that this option is incorrect.

Option (D): Imine Formation with \(\mathrm{NHZ}_{2}\)

The formation of an imine involves the reaction between a carbonyl compound (aldehyde or ketone) and a primary amine, resulting in a Schiff base. The statement tells us that if we use \(\mathrm{NHZ}_{2}\) in place of \(\mathrm{H}_{2}\mathrm{N}-\mathrm{Z}\), then an imine will be obtained as (Q). This statement is true for primary amines, as imines would be formed in such a reaction. Upon analyzing all the options, none of them seem to be incorrect based on the limited information given in the exercise. It is possible that an error has been made in the question or the problem requires more context to deduce the incorrect option.

Key concepts

Acid Catalysis in Organic Chemistry

Acid catalysis plays a crucial role in organic chemistry by providing an alternative pathway for a reaction with a lower activation energy. It often involves the donation of protons to the reactant molecules to increase the rate of reaction. This process is widely used in synthesizing many compounds. For example, in a reversible reaction where equilibrium is involved, an acid catalyst can help achieve desired products more efficiently.

Understanding the Role of Acid in Catalysis

Acids can protonate nucleophiles or activate electrophiles, thus facilitating the bond formation or bond cleavage necessary for the progress of the reaction. An acid catalyst is typically a strong acid, and it comes back unchanged at the end of the reaction cycle, ready to participate in another reaction.

Substituents in Organic Reactions

Substituents are atoms or groups of atoms that are attached to the carbon backbone of an organic molecule. They can greatly influence the behavior of the molecule in chemical reactions. Factors such as the size, electronic properties, and the ability to donate or withdraw electrons make different substituents affect the reaction outcomes in various ways.

Electron Donating and Withdrawing Effects

Electron-donating groups can activate the molecule towards nucleophilic attack, while electron-withdrawing groups can deactivate it. Understanding how these substituents interact with the main framework of the organic compound is key to predicting the product distribution of a reaction.

Dehydration Reactions

Dehydration reactions involve the loss of a water molecule from a reactant. In organic chemistry, this process is crucial for the formation of double bonds in alkenes or the synthesis of ethers. Dehydration typically requires an acid catalyst to proceed.

Mechanism and Thermodynamic Considerations

During a dehydration reaction, an alcohol, for instance, might first be protonated by an acid, increasing its tendency to lose a water molecule. The resulting carbocation is a key intermediate that will lead to the desired alkene upon elimination. This reaction is generally favored by high temperatures and can be a part of a mechanism with several steps, including the production of more stable (and thus more favored) products.

Imine Formation

Imines are nitrogen-containing compounds formed via the condensation of carbonyl compounds with primary amines. This reaction initially forms a carbinolamine intermediate, which then dehydrates to yield an imine, often requiring an acid catalyst.

Significance of Imines

Imines are significant intermediates in organic synthesis and can give rise to a variety of other compounds through further reactions, including amines, amides, and other nitrogenous functionalities. The choice of primary amine, including its substituents, can lead to diverse structures in the realm of imine derivatives.