Phenol treated with chloroform in presence of sodium hydroxide, which further hydrolysed in presence of an acid results

Solution & Explanation

Related Formula
Phenol + CHCl₃ + NaOH H^+ 2-Hydroxybenzaldehyde (Salicylaldehyde)
Core Logic

This chemical sequences details the well-known Reimer-Tiemann reaction mechanism. The treatment of phenol with alkaline chloroform generates a dichlorocarbene intermediate (:CCl₂), which acts as an electrophile and specifically attacks the ortho position of the phenoxide ring system.

Subsequent basic hydrolysis converts the functional intermediate to an aldehyde block, providing 2-hydroxybenzaldehyde as the major final product.

Step 1: Visual Pathway Validation

The step-by-step schematic transforms structural blocks through standard intermediates:

Reimer-Tiemann Reaction solution diagram for Q68 - JEE Main 2024 Evening
Reimer-Tiemann Reaction solution diagram for Q68 - JEE Main 2024 Evening

Pattern Recognition

Chloroform + Base + Phenol yields formylation at the ortho site, producing salicylaldehyde (2-hydroxybenzaldehyde).

Chapter Mix

Class 12 Chemistry: Organic Compounds Containing Oxygen

More Organic Compounds Containing Oxygen 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) 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).

Reaction 2: Hydroboration-Oxidation (B₂H₆, then H₂O₂/NaOH) This proceeds via anti-Markovnikov addition of water across the double bond without carbocation rearrangement. The OH group adds to the less substituted carbon atom of the alkene (product B: Ph-CH₂-CH₂-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 = Markovnikov hydration (carbocation intermediate). B₂H₆ / H₂O₂, 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.
  • B. 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 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.
  • B. 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 of around 10.0, and ethanol has a pKₐ of around 15.9.

Reason R is false: A lower pKₐ 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

Rankbit System
JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%) | JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%)