Question

Select the correct option(s). (A) Kucherov's reaction (1\% \(\mathrm{HgSO}_{4}\), dil. \(\left.\mathrm{H}_{2} \mathrm{SO}_{4}\right)\) is nucleophilic addition reaction (B) Benzaidehyde is more reactive in nucleophilic addition than propanal because resonance wì increase the polarity of carbonyl group (C) \(p\)-Nitrobenzaldehyde \(>\) Benzaldehyde \(>\) Acetophenone \(>p\)-Tolualdehyde (Reactivity in Nu-addition) (D) Butanal is more polar than ethoxyethane. Therefore, intermolecular dipole- dipole attractiod? stronger in butanal

Short answer

The correct options are (A) and (D). Kucherov's reaction is a nucleophilic addition reaction, and butanal is more polar than ethoxyethane, leading to stronger intermolecular dipole-dipole interactions.

Step-by-step solution

(A)Kucherov's Reaction

Kucherov's reaction involves the addition of an organometallic reagent (Grignard reagent or organolithium compound) to a carbonyl group to form an alcohol. This reaction is a nucleophilic addition because the negatively charged organometallic reagent is a strong nucleophile and adds to the carbonyl group, which is electrophilic. Thus, this statement is true.

(B)Benzaldehyde vs. Propanal reactivity

Benzaldehyde has a phenyl group attached to the carbonyl group, which allows for resonance stabilization. This delocalization of electrons decreases the electrophilicity of the carbonyl carbon and, therefore, lowers the reactivity of benzaldehyde in nucleophilic addition reactions when compared to propanal. Therefore, this statement is false.

(C)Reactivity order

The reactivity order for nucleophilic addition reactions is determined by the degree of electrophilicity of the carbonyl carbon. This order should be: \(p\)-Nitrobenzaldehyde \(>\) Benzaldehyde \(>\) \(p\)-Tolualdehyde \(>\) Acetophenone. The given order in the statement is incorrect, so the statement is false.

(D)Polarity of Butanal vs. Ethoxyethane

Butanal is an aldehyde and contains a polar carbonyl group. Therefore, it exhibits intermolecular dipole-dipole interactions. Ethoxyethane (also known as diethyl ether) has two nonpolar ethyl groups and exhibits only weak van der Waals forces. Thus, butanal is more polar than ethoxyethane, and its intermolecular forces are stronger. The statement is true. In conclusion, the correct options are (A) and (D).

Key concepts

Kucherov's Reaction

Kucherov's reaction is a classic chemical transformation often discussed in organic chemistry. In this reaction, an organometallic reagent, either a Grignard reagent or an organolithium compound, acts as a strong nucleophile. What sets this reaction apart is its mechanism: the organometallic reagent, rich in electrons, targets the electrophilic carbon atom of a carbonyl group—a carbon atom doubly bonded to oxygen, which is partially positive.
Adding the nucleophile leads to the formation of an alcohol. This forms the basis for calling it a 'nucleophilic addition reaction,' where the nucleophile adds to the carbonyl group. Essential steps include the attack by the nucleophile followed by protonation to form the final alcohol product. Understanding Kucherov's reaction helps conceptualize how organometallic compounds can transform carbonyl groups into alcohols. Overall, knowing this reaction aids in grasping broader concepts of nucleophilic addition and the behavior of electron-rich compounds in organic synthesis.

Carbonyl Group Reactivity

Carbonyl groups, characterized by a carbon-oxygen double bond, exhibit unique reactivity patterns in organic compounds. The carbon atom is electrophilic, which means it attracts electrons, while the oxygen atom is partially negative due to oxygen's higher electronegativity. This polar nature makes carbonyl groups significant targets for nucleophilic addition reactions.
The reactivity of a carbonyl group depends heavily on its surrounding molecular environment. Consider benzaldehyde versus propanal as an example. Benzaldehyde, which includes a benzene ring, experiences resonance stabilization. This means the electron-rich benzene ring delocalizes some electron density, reducing the carbonyl carbon's electrophilicity. Conversely, propanal lacks such stabilization, making it more reactive to nucleophiles. Understanding these differences helps chemists predict how various carbonyl-containing compounds will behave in reactions. It highlights how structural components like aromatic rings can influence electrophilicity and, consequently, reactivity. These insights are crucial when planning synthetic routes in organic chemistry.

Polarity in Organic Compounds

Polarity is a cornerstone concept in chemistry that influences many physical properties, such as boiling and melting points, solubility, and intermolecular interactions. In organic compounds, polarity primarily stems from differences in electronegativity between atoms, leading to dipole moments within molecules.
Butanal and ethoxyethane present an excellent case study. Butanal contains a highly polar carbonyl group. This not only contributes to its polarity but also facilitates stronger intermolecular dipole-dipole forces, making it more "sticky" so to speak, leading to higher boiling points compared to nonpolar ether compounds like ethoxyethane. These differences are crucial across various fields: understanding them aids in interpreting reactions' behaviors, predicting physical properties, and determining compound applications. For students, grasping the concept of polarity is instrumental, whether you're focusing on reaction mechanisms or more practical applications like extraction and purification processes.