Answer the question on the basis of passage given below:

Strong oxidizing agents, oxidize toluene and its derivatives to benzoic acid. However, it is possible to stop the oxidation at the aldehyde stage with suitable reagents that convert methyl group to an intermediate that is difficult to oxidize further.

Conversions that can be done by same reagent are:

A. Benzaldehyde to 2-Nitrobenzaldehyde

B. Propan-1-ol to Propanal

C. Pent-3-en-2-ol to Pent-3-en-2-one

D. Butanal to Butan-1-ol

E. Methanal to Ethanol

Choose the correct answers from the options given below:

B and C only

The correct answer is option 1. B and C only.

Let us delve into the detailed explanation of each conversion and identify the common reagents used:

A. Benzaldehyde to 2-Nitrobenzaldehyde

This is a nitration reaction.

Reagent: Nitrating mixture (concentrated nitric acid and concentrated sulfuric acid).

Nitration involves the introduction of a nitro group (\(-NO_2\)) into the benzene ring of benzaldehyde. The nitronium ion (\(NO_2^+\)) is generated from the nitrating mixture and attacks the benzene ring in an electrophilic aromatic substitution reaction. This reaction does not involve oxidation or reduction but rather an electrophilic aromatic substitution.

B. Propan-1-ol to Propanal

This is an oxidation reaction.

Reagent: Pyridinium chlorochromate (PCC) or Chromium trioxide \((CrO_3)\) in acidic conditions.

PCC and CrO₃ are used to oxidize primary alcohols to aldehydes. Propan-1-ol (a primary alcohol) is oxidized to Propanal (an aldehyde). This reaction involves the removal of two hydrogen atoms: one from the hydroxyl group and one from the carbon adjacent to the hydroxyl group.

C. Pent-3-en-2-ol to Pent-3-en-2-one

This is an oxidation reaction.

Reagent: Pyridinium chlorochromate (PCC) or Chromium trioxide (CrO₃).

PCC or CrO₃ can be used to oxidize secondary alcohols to ketones. Pent-3-en-2-ol (a secondary alcohol) is oxidized to Pent-3-en-2-one (a ketone). This reaction involves the removal of hydrogen atoms from the secondary alcohol group.

D. Butanal to Butan-1-ol

This is a reduction reaction.

Reagent: Lithium aluminium hydride (LiAlH₄) or Sodium borohydride (NaBH₄).

LiAlH₄ and NaBH₄ are reducing agents that reduce aldehydes to primary alcohols. Butanal (an aldehyde) is reduced to Butan-1-ol (a primary alcohol). This involves the addition of hydride ions (\(H^-\)) to the carbonyl group, converting the aldehyde to an alcohol.

E. Methanal to Ethanol

This is a Grignard reaction.

Reagent: Grignard reagent (e.g., Methylmagnesium bromide) followed by acidic workup.

The Grignard reagent reacts with Methanal (formaldehyde) to form a primary alcohol (Ethanol) after hydrolysis. The Grignard reagent adds a methyl group to the carbonyl carbon, and then the intermediate alkoxide is hydrolyzed to yield the alcohol.

Reagents Analysis:

1. Nitration Reagents (for A):

Nitrating mixture (conc. HNO₃ and conc. H₂SO₄) is used to introduce nitro groups into aromatic rings. This is different from oxidation and reduction reactions.

2. Oxidizing Agents (for B and C):

PCC (Pyridinium Chlorochromate) and CrO₃ (Chromium Trioxide) are used for oxidation reactions. PCC oxidizes primary alcohols to aldehydes and secondary alcohols to ketones. CrO₃ can perform similar oxidation reactions under acidic conditions.

3. Reducing Agents (for D):

LiAlH₄ (Lithium Aluminium Hydride) and NaBH₄ (Sodium Borohydride) are reducing agents. LiAlH₄ and NaBH₄ reduce aldehydes to primary alcohols and ketones to secondary alcohols.

4. Grignard Reagents (for E):

Grignard reagents (e.g., Methylmagnesium bromide) react with aldehydes or ketones to form alcohols. Grignard reagents are used for adding carbon chains to carbonyl compounds and converting them to alcohols.

Conclusion:

Common Reagents: PCC and CrO₃ are common reagents that can perform both the conversion of Propan-1-ol to Propanal and Pent-3-en-2-ol to Pent-3-en-2-one.

Therefore, the correct answer is: Option 1: B and C only, as both conversions can be accomplished with the same reagents (PCC or CrO₃).