A toxic compound “A” when reacted with NaCN in aqueous acidic medium yields an edible cooking component and food preservative “B”. “B” is converted to “C” by diborane and can be used as an additive to petrol to reduce emission. “C” upon reaction with oleum at 140 yields an inhalable anesthetic “D”. Identify “A”, “B”, “C” and “D”, respectively.

Let's track the conversions row by row based on the description: 1. Toxic compound **A** is methanol (CH3OH). Reacting it via acidic NaCN sequences effectively converts it eventually into acetic acid (CH3COOH), which is an edible cooking component and food preservative (vinegar) **B**. 2. Reduction of acetic acid (**B**) with diborane (B2H6) yields ethanol (CH3CH2OH) **C**. Ethanol is used as a biofuel additive in petrol. 3. Ethanol (**C**) upon heating with oleum/concentrated sulfuric acid at 140 undergoes intermolecular dehydration to yield diethyl ether (C2H5-O-C2H5) **D**, which functions as an inhalable anesthetic. The full sequential progression corresponds exactly to: Key temperature indicator: Dehydration of ethanol at 140 yields diethyl ether (ether synthesis), whereas 170 yields ethene gas. Combined with the food preservative clue (acetic acid), the sequence locks instantly to option (3). Class 12 Chemistry: Alcohols, Phenols and Ethers

A toxic compound “A” when reacted with NaCN in aqueous acidic medium yields an edible cooking component and food preservative “B”. “B” is converted to “C” by diborane and can be used as an additive to

Let's track the conversions row by row based on the description: 1. Toxic compound **A** is methanol (CH3OH). Reacting it via acidic NaCN sequences effectively converts it eventually into acetic acid (CH3COOH), which is an edible cooking component and food preservative (vinegar) **B**. 2. Reduction of acetic acid (**B**) with diborane (B2H6) yields ethanol (CH3CH2OH) **C**. Ethanol is used as a biofuel additive in petrol. 3. Ethanol (**C**) upon heating with oleum/concentrated sulfuric acid at 1

A toxic compound “A” when reacted with NaCN in aqueous acidic medium yields an edible cooking component and food preservative “B”. “B” is converted to “C” by diborane and can be used as an additive to petrol to reduce emission. “C” upon reaction with oleum at 140 yields an inhalable anesthetic “D”. Identify “A”, “B”, “C” and “D”, respectively.

Let's track the conversions row by row based on the description: 1. Toxic compound **A** is methanol (CH3OH). Reacting it via acidic NaCN sequences effectively converts it eventually into acetic acid (CH3COOH), which is an edible cooking component and food preservative (vinegar) **B**. 2. Reduction of acetic acid (**B**) with diborane (B2H6) yields ethanol (CH3CH2OH) **C**. Ethanol is used as a biofuel additive in petrol. 3. Ethanol (**C**) upon heating with oleum/concentrated sulfuric acid at 140 undergoes intermolecular dehydration to yield diethyl ether (C2H5-O-C2H5) **D**, which functions as an inhalable anesthetic. The full sequential progression corresponds exactly to: Key temperature indicator: Dehydration of ethanol at 140 yields diethyl ether (ether synthesis), whereas 170 yields ethene gas. Combined with the food preservative clue (acetic acid), the sequence locks instantly to option (3). Class 12 Chemistry: Alcohols, Phenols and Ethers

A toxic compound “A” when reacted with NaCN in aqueous acidic medium yields an edible cooking component and food preservative “B”. “B” is converted to “C” by diborane and can be used as an additive to

Let's track the conversions row by row based on the description: 1. Toxic compound **A** is methanol (CH3OH). Reacting it via acidic NaCN sequences effectively converts it eventually into acetic acid (CH3COOH), which is an edible cooking component and food preservative (vinegar) **B**. 2. Reduction of acetic acid (**B**) with diborane (B2H6) yields ethanol (CH3CH2OH) **C**. Ethanol is used as a biofuel additive in petrol. 3. Ethanol (**C**) upon heating with oleum/concentrated sulfuric acid at 1

A toxic compound “A” when reacted with NaCN in aqueous acidic medium yields an edible cooking component and food…

Year	2026	2025	2024	Total
Questions	7	5	11	23

Year

2026

2025

2024

Total

Questions

Solution & Explanation

Core Logic

Let's track the conversions row by row based on the description:

Toxic compound A is methanol ( $CH₃OH$ $CH_3OH$). Reacting it via acidic NaCN sequences effectively converts it eventually into acetic acid ( $CH₃COOH$ $CH_3COOH$), which is an edible cooking component and food preservative (vinegar) B.
Reduction of acetic acid (B) with diborane ( $B₂H₆$ $B_2H_6$) yields ethanol ( $CH₃CH₂OH$ $CH_3CH_2OH$) C. Ethanol is used as a biofuel additive in petrol.
Ethanol (C) upon heating with oleum/concentrated sulfuric acid at $140°C$ $140^{\circ}\mathrm{C}$ undergoes intermolecular dehydration to yield diethyl ether ( $C₂H₅-O-C₂H₅$ $C_2H_5-O-C_2H_5$) D, which functions as an inhalable anesthetic.

Step 1: Chemical Reaction Sequence Flow

Chemical flow chart for sequential ether preparation

The full sequential progression corresponds exactly to:

Methanol (A) arrow Acetic Acid (B) arrow Ethanol (C) arrow Diethyl ether (D)

Pattern Recognition

Key temperature indicator: Dehydration of ethanol at $140°C$ $140^{\circ}\mathrm{C}$ yields diethyl ether (ether synthesis), whereas $170°C$ $170^{\circ}\mathrm{C}$ yields ethene gas. Combined with the food preservative clue (acetic acid), the sequence locks instantly to option (3).

Chapter Mix

Class 12 Chemistry: Alcohols, Phenols and Ethers

More Alcohols, Phenols and Ethers Previous-Year Questions — Page 5

Q jee_main_2024_30_january_evening Preparation of Alcohols

Product A and B formed in the following set of reactions are:

Preparation of Alcohols diagram for Q66 - JEE Main 2024 Evening — The diagram shows a reaction pathway for synthesizing product A and B.

A. $A = CH₂OH , B = CH₂OH$
B. $A = CH₃OH , B = CH₃OH$
C. $A = CH₂OH , B = CH₃OH$
D. $A = CH₃OH , B = CH₃OH$

Solution

Core Logic

The given substrate is an alkene attached to a benzene ring (styrene derivative).

Reaction 1: Acid-catalyzed hydration ( $H^+ / H₂O$ $H^+ / H_2O$) This proceeds via Markovnikov's rule. The proton attacks the alkene to form the most stable carbocation (benzyllic and secondary). Water then attacks this carbocation to yield the alcohol at the substituted position (product A: $Ph-CH(OH)-CH₃$ $Ph-CH(OH)-CH_3$).

Reaction 2: Hydroboration-Oxidation ( $B₂H₆$ $B_2H_6$, then $H₂O₂/NaOH$ $H_2O_2/NaOH$) This proceeds via anti-Markovnikov addition of water across the double bond without carbocation rearrangement. The $OH$ $OH$ group adds to the less substituted carbon atom of the alkene (product B: $Ph-CH₂-CH₂-OH$ $Ph-CH_2-CH_2-OH$).

Reaction pathway for products A and B diagram for Q66 - JEE Main 2024 Evening — The diagram shows a reaction pathway for synthesizing product A and B.

Pattern Recognition

$H^+/H₂O$ $H^+/H_2O$ = Markovnikov hydration (carbocation intermediate). $B₂H₆ / H₂O₂, OH^-$ $B_2H_6 / H_2O_2, OH^-$ = Anti-Markovnikov hydration (concerted, no rearrangement).

Chapter Mix

Class 12 Chemistry: Alcohols Phenols and Ethers Class 11 Chemistry: Hydrocarbons

Q69 jee_main_2024_31_jan_morning Chemical Reactions of Alcohols

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R: Assertion A: Alcohols react both as nucleophiles and electrophiles. Reason R: Alcohols react with active metals such as sodium, potassium and aluminum to yield corresponding alkoxides and liberate hydrogen. In the light of the above statements, choose the correct answer from the options given below:

A. $A is false but R is true.$ $\text{A is false but R is true.}$
B. $A is true but R is false.$ $\text{A is true but R is false.}$
C. $Both A and R are true and R is the correct explanation of A.$
D. $Both A and R are true but R is NOT the correct explanation of A.$

Solution

Core Logic

Assertion (A) is correct. Alcohols can act as nucleophiles (in reactions involving O-H bond cleavage) and as electrophiles (in reactions involving C-O bond cleavage after protonation).

Reason (R) is correct. Alcohols react with active metals to form alkoxides and $H₂$ $H_2$ gas.

However, Reason (R) only explains the acidic nature of the O-H bond (which relates to nucleophilic behavior when broken) but does not explain the electrophilic behavior (C-O cleavage). Thus, (R) is not the correct explanation for (A).

Chapter Mix

Class 12 Chemistry: Alcohols, Phenols and Ethers

Q74 jee_main_2024_31_jan_morning Acidity of Phenols

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R: Assertion A:

pKₐ

value of phenol is 10.0 while that of ethanol is 15.9. Reason R: Ethanol is stronger acid than phenol. In the light of the above statements, choose the correct answer from the options given below:

A. $A is true but R is false.$ $\text{A is true but R is false.}$
B. $A is false but R is true.$ $\text{A is false but R is true.}$
C. $Both A and R are true and R is the correct explanation of A.$
D. $Both A and R are true but R is NOT the correct explanation of A.$

Solution

Core Logic

Assertion A is true: Phenol has a $pKₐ$ $pK_a$ of around 10.0, and ethanol has a $pKₐ$ $pK_a$ of around 15.9.

Reason R is false: A lower $pKₐ$ $pK_a$ value implies higher acidity. Therefore, phenol is a stronger acid than ethanol. This is because the conjugate base of phenol (phenoxide ion) is resonance-stabilized, whereas the ethoxide ion is destabilized by the +I effect of the ethyl group.

Chapter Mix

Class 12 Chemistry: Alcohols, Phenols and Ethers

Solution & Explanation

Core Logic

Step 1: Chemical Reaction Sequence Flow

Pattern Recognition

Chapter Mix

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More Alcohols, Phenols and Ethers Previous-Year Questions — Page 5

Solution

Core Logic

Pattern Recognition

Chapter Mix

Solution

Core Logic

Chapter Mix

Solution

Core Logic

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