In Reimer - Tiemann reaction, phenol is converted into salicylaldehyde through an intermediate. The structure of intermediate is __________.

Solution

Chemistry ma’am · 4 steps

Follow chloroform's carbon: it enters the ring as -CHCl₂ while phenol stays a phenoxide.

1. Make the electrophile. In strong base, chloroform loses H⁺ and then Cl⁻. This gives dichlorocarbene, CCl₂, an electron-poor carbon with only six electrons around it.

   CHCl₃ + OH⁻ → CCl₂ + Cl⁻ + H₂O

2. Ortho attack. In NaOH, phenol is present as sodium phenoxide, and its -O⁻ makes the ring very electron-rich. The ring attacks CCl₂ at the ortho position, and the new carbon picks up a hydrogen. The result is sodium o-(dichloromethyl)phenoxide, with -CHCl₂ next to -O⁻Na⁺.
3. Then the aldehyde. Aqueous alkali replaces both Cl atoms on that carbon, and the gem-diol that forms loses water to give -CHO as sodium salicylaldehyde. Adding acid at the very end gives salicylaldehyde.
4. So. The intermediate is the dichloromethyl compound, still in its phenoxide form, with -CHCl₂ beside -O⁻Na⁺. That is option (b).

The idea to keep. In Reimer-Tiemann, CHCl₃ gives CCl₂, which goes ortho on phenoxide as -CHCl₂. Hydrolysis turns it into -CHO. Everything stays as a sodium salt until the final acid step.

Answer from the NTA final answer key. Solution by PrepWiser.