Question

Choose the correct option regarding following reaction : \((\mathrm{P}) \stackrel{\mathrm{H}_{2} / \mathrm{Ni}}{\longrightarrow}(\mathrm{Q})\) (A) (P) is thioketal (B) IUPAC name of ' \(\mathrm{Q}\) ' is methyl cyclohexane (C) Formation of \((\mathrm{P})\) is electrophilic addition reaction (D) \((\mathrm{Q})\) is formed by hydrogenation of \((\mathrm{P})\)

Short answer

Option (D) is the correct answer. $\mathrm{(Q)}$ is formed by hydrogenation of $\mathrm{(P)}$.

Step-by-step solution

Identifying the Reaction

The given reaction is a hydrogenation reaction, where a substrate \((\mathrm{P})\) is treated with hydrogen gas \((\mathrm{H}_{2})\) in the presence of a catalyst, in this case, Nickel \((\mathrm{Ni})\). This reaction would result in the formation of the product \((\mathrm{Q})\).

Examine Option A

Option A states that (P) is a thioketal. Thioketals are sulfur analogs of ketals and are formed by adding two equivalents of a thiol to a ketone. The hydrogenation reaction can be carried out on thioketals, so this option could be correct.

Examine Option B

Option B suggests that the IUPAC name of ' \(\mathrm{Q}\) ' is methyl cyclohexane. Since \(\mathrm{Q}\) is the product of the hydrogenation of \(\mathrm{P}\), if \(\mathrm{P}\) is a suitable substrate for the reaction and upon hydrogenation becomes methyl cyclohexane, then this option can also be correct.

Examine Option C

Option C states that the formation of \((\mathrm{P})\) is an electrophilic addition reaction. Electrophilic addition reactions usually involve unsaturated hydrocarbons like alkenes and alkynes. Hydrogenation reactions typically involve reduction of unsaturated compounds, which may include those formed via electrophilic addition reactions. So, option C could also be correct.

Examine Option D

Option D asserts that \((\mathrm{Q})\) is formed by hydrogenation of \((\mathrm{P})\). This statement is true, as it is the given reaction \((\mathrm{P}) \stackrel{\mathrm{H}_{2} /\mathrm{Ni}}{\longrightarrow}(\mathrm{Q})\). Thus, option D is correct.

Determine the Correct Option

All the options (A), (B), (C), and (D) seem to be true. However, the exercise mentions choosing "the correct option," implying there is only one correct answer among them. Option D is the most general option, which describes the given reaction directly. Therefore, option D is the correct answer.

Key concepts

Thioketal

A thioketal is an organosulfur compound characterized by a carbon atom connected to two sulfur atoms and two alkyl or aryl groups. Structurally similar to an acetal but with sulfur replacing the oxygen atoms, thioketals are typically prepared through the reaction of ketones with thiols.

Thioketals display unique chemical properties due to the presence of sulfur atoms. They are often used in organic synthesis because they can act as protecting groups for carbonyl compounds, making them resistant to certain reactions. When used as such, thioketals can be converted back into the carbonyl compounds by desulfurization. In hydrogenation reactions, the sulfur atoms do not interfere and the hydrocarbon portions can be readily hydrogenated in the presence of suitable catalysts, like nickel.

IUPAC Nomenclature

IUPAC nomenclature is an internationally recognized system for naming chemical compounds established by the International Union of Pure and Applied Chemistry (IUPAC). Its purpose is to ensure that each compound has a unique and descriptive name.

The naming process involves several rules to determine the base name of the compound, which corresponds to the longest continuous chain of carbon atoms. Prefixes and suffixes are then added to identify substituents, functional groups, and other modifications. For example, the IUPAC name for 'Q' would depend on the structure of 'P' and how it changes during hydrogenation. If 'P' is a cyclic alkene and hydrogenation results in a fully saturated ring with a methyl group as a substituent, the product 'Q' would be named methylcyclohexane.

Electrophilic Addition Reaction

Electrophilic addition is a fundamental type of reaction in organic chemistry where an electrophile and a nucleophile combine to form a more stable molecule. Unsaturated hydrocarbons, like alkenes and alkynes, are common substrates because they have double or triple bonds, which are electron-rich sites.

During an electrophilic addition reaction, the π bond of the unsaturated hydrocarbon is broken and two new sigma (σ) bonds are formed. Electrophiles, being electron-deficient, attack the electron-rich double bond, followed by nucleophiles joining to the positively charged intermediate. Hydrogenation can be seen as a form of electrophilic addition where molecular hydrogen (H2) is the electrophile and the unsaturated bond acts as the nucleophile.

Unsaturated Hydrocarbons

Unsaturated hydrocarbons are organic compounds that contain double or triple bonds between carbon atoms. These include alkenes (with one double bond), alkynes (with one triple bond), and arenes (aromatic hydrocarbons with alternating double bonds).

Due to the presence of double or triple bonds, unsaturated hydrocarbons are more reactive than their saturated counterparts, which only have single bonds. The double or triple bonds allow for reactions such as hydrogenation, where hydrogen is added across the bond, converting unsaturated hydrocarbons to saturated hydrocarbons. The increased reactivity makes unsaturated hydrocarbons key players in electrophilic addition reactions.