Which of the following statements are correct?

A. Dry ether is used in Wurtz reaction

B. Grignard reagent is an example of organo metallic compound.

C. Bond cleavage of \(C-Cl\) is easier in haloarene than haloalkane

D. Chlorobenzene does not show Friedel Craft reaction.

E. Enantiomers differ with respect to rotation of plane polarized light.

Choose the correct amnswer from the options given below:

A, B, E only

The correct answer is option 3. A, B, E only.

Let us look at each of the statements in detail:

A. Dry ether is used in Wurtz reaction: The given statement is correct.

The Wurtz reaction involves the coupling of two alkyl halides using sodium metal to form a new alkane. The general reaction is:

\(2 R-X + 2 Na \rightarrow R-R + 2 NaX \)

where \( R-X \) represents an alkyl halide, and \( R-R \) is the newly formed alkane.

Role of Dry Ether

Prevents Reaction with Water:

Sodium metal is highly reactive with water. In the presence of water, sodium reacts to form sodium hydroxide (NaOH) and hydrogen gas (H₂):

\(2 Na + 2 H_2O \rightarrow 2 NaOH + H_2 \)

This reaction not only consumes sodium metal but also produces hydrogen gas, which is dangerous and would interfere with the Wurtz reaction.

Solvent Properties:

Ether serves as a suitable solvent because it dissolves both the sodium metal and the alkyl halides effectively. It helps in creating a homogeneous reaction mixture where the sodium metal and alkyl halides can interact. Ether is non-polar and provides a stable environment for the reaction.

Stabilizes Reactive Intermediates:

During the Wurtz reaction, reactive intermediates like alkyl radicals or carbanions are formed. Ether helps in stabilizing these intermediates, facilitating their combination to form the final product.

Inert Nature:

Dry ether is relatively inert to the reactants involved in the Wurtz reaction. This means it does not participate in the reaction or undergo significant side reactions, ensuring that the reaction proceeds as intended.

The term "dry" indicates that the ether is free of water. Any moisture or water present could react with the sodium metal, reduce its effectiveness, and lead to side reactions. Therefore, dry ether is essential for the successful execution of the Wurtz reaction. In summary, dry ether is crucial in the Wurtz reaction because it prevents the sodium from reacting with water, provides an appropriate solvent environment, and stabilizes reactive intermediates, ensuring a successful and safe reaction.

B. Grignard reagent is an example of organo metallic compound: The statement is correct.

A Grignard reagent is indeed an example of an organo-metallic compound. Let me break it down:

Organometallic compounds are substances that contain a metal-carbon bond where the metal is typically a metal from groups 1, 2, or 13, or sometimes a transition metal, and the carbon is part of an organic group.

Grignard reagents have the general formula RMgX, where R is an organic group (such as an alkyl or aryl group), Mg is magnesium, and X is a halogen (such as chlorine, bromine, or iodine). In this structure, the carbon-magnesium bond is the key feature of Grignard reagents.

The carbon-magnesium bond in Grignard reagents makes them organometallic. The organic group (R) is bonded to magnesium, which is a metal, hence fitting the definition of organometallic compounds.

Grignard reagents are highly reactive and are used extensively in organic synthesis, especially in reactions involving the formation of carbon-carbon bonds. This reactivity is a result of the polar nature of the carbon-magnesium bond, where the carbon atom has a partial negative charge, making it a strong nucleophile.

In summary, Grignard reagents are classified as organometallic compounds because they contain a metal-carbon bond, specifically magnesium in this case.

C. Bond cleavage of \(C-Cl\) is easier in haloarene than haloalkane: The statement is incorrect.

The statement that "Bond cleavage of \(C−Cl\) is easier in haloarene than haloalkane" is indeed incorrect.

Bond Strength and Bonding Environment:

In haloalkanes, the \(C−Cl\) bond is typically a single bond between a carbon atom and a chlorine atom, with the bond strength around 328 kJ/mol. In haloarenes (such as chlorobenzene), the \(C−Cl\) bond is part of an aromatic ring. This bond is more complex due to the delocalization of π-electrons in the aromatic system, which affects the bond strength.

Resonance and Aromaticity:

In haloarenes, the chlorine atom is bonded to a carbon in an aromatic ring. The lone pair of electrons on the chlorine can interact with the π-electron system of the benzene ring through resonance. This interaction stabilizes the \(C−Cl\) bond in haloarenes.The resonance stabilization in haloarenes makes the \(C−Cl\) bond stronger compared to haloalkanes.

Bond Cleavage:

In haloalkanes, the \(C−Cl\) bond can be cleaved more readily, often through nucleophilic substitution reactions where the chlorine is displaced by a nucleophile.In haloarenes, the cleavage of the \(C−Cl\) bond is much less favorable due to the additional stabilization provided by the aromatic system. Breaking this bond requires more energy.In summary, the \(C−Cl\) bond in haloarenes is stronger and less reactive compared to haloalkanes because of the additional resonance stabilization provided by the aromatic ring. Thus, bond cleavage of \(C−Cl\) is more challenging in haloarenes than in haloalkanes.

D. Chlorobenzene does not show Friedel Craft reaction: This statement is incorrect.

The statement "Chlorobenzene does not show Friedel-Crafts reaction" is incorrect because chlorobenzene does indeed undergo Friedel-Crafts reactions, but with some caveats. Here is a detailed explanation:

Friedel-Crafts reactions are a set of chemical reactions involving the alkylation or acylation of an aromatic ring, typically using a Lewis acid catalyst like \(AlCl_3\). There are two main types:

Friedel-Crafts Alkylation: Addition of an alkyl group to an aromatic ring.

Friedel-Crafts Acylation: Addition of an acyl group \((R-CO)\) to an aromatic ring.

Friedel-Crafts Alkylation:

In this reaction, an alkyl halide reacts with the aromatic ring in the presence of a Lewis acid catalyst (e.g., \(AlCl_3\)) to form an alkylated aromatic product.

Chlorobenzene can be used as a substrate in Friedel-Crafts alkylation reactions. However, the reaction is generally less effective compared to benzene. This reduced reactivity is due to the presence of the electron-withdrawing chlorine atom, which deactivates the aromatic ring and makes it less nucleophilic.

The chlorine atom is a deactivating group due to its electron-withdrawing inductive effect, which reduces the electron density of the ring and slows down the reaction.

Friedel-Crafts Acylation:

In this reaction, an acyl chloride \((R-COCl)\) reacts with the aromatic ring in the presence of a Lewis acid catalyst (e.g., \(AlCl_3\)) to form an acylated aromatic product. Chlorobenzene can undergo Friedel-Crafts acylation more readily than alkylation. The reaction is generally successful due to the fact that the electron-withdrawing nature of chlorine is less pronounced in this case compared to alkylation.

So, while the Friedel-Crafts alkylation of chlorobenzene might be less efficient, chlorobenzene is indeed capable of participating in Friedel-Crafts reactions.

E. Enantiomers differ with respect to rotation of plane polarized light: The given statement is correct.

Enantiomers are a type of stereoisomer that are non-superimposable mirror images of each other. They are also known as optical isomers because they have the property of rotating plane-polarized light in different directions. When plane-polarized light passes through a chiral substance (one that has non-superimposable mirror images), its plane of polarization is rotated. This phenomenon is known as optical rotation. Enantiomers are characterized by their ability to rotate plane-polarized light in opposite directions. One enantiomer will rotate the light clockwise (dextrorotatory or "+"), while its mirror image will rotate it counterclockwise (levorotatory or "−"). Enantiomers are chiral, meaning they lack an internal plane of symmetry and cannot be superimposed on their mirror images. This chirality leads to differences in their interaction with plane-polarized light. The degree of rotation and the direction (clockwise or counterclockwise) are measured using a polarimeter. This measurement helps in distinguishing between enantiomers in a mixture. Enantiomers are related as mirror images of each other, similar to how your left and right hands are mirror images. Although they have the same physical and chemical properties in an achiral environment, their interactions with polarized light are different. Enantiomers differ in their ability to rotate plane-polarized light due to their chiral nature. This difference in optical rotation is a fundamental characteristic of enantiomers and is used to identify and separate them in various applications, such as in pharmaceuticals, where the activity of a drug can be dependent on its specific enantiomer.