Reimer–Tiemann reaction template

Base turns CHCl₃ into :CCl₂, phenoxide attacks it at the ortho carbon and hydrolysis of the CHCl₂ group gives salicylaldehyde.

Mechanism step by step

Dichlorocarbene from chloroform formylates a phenoxide at the ortho position

1. Dichlorocarbene – NaOH deprotonates CHCl₃; CCl₃⁻ then loses Cl⁻
2. Attack on the carbene – The ortho carbon of phenoxide attacks
3. Tautomerisation – Proton transfer restores the aromatic ring

Key points

• First, hydroxide removes the C–H proton of chloroform to give CCl₃⁻.
• Hydroxide then hydrolyses the CHCl₂ group to CHO; acid work-up gives salicylaldehyde.
• Ortho attack dominates; some para product forms.
• Dichlorocarbene is an electron-poor (singlet) carbene: a lone pair and an empty orbital.
• With CCl₄ instead of CHCl₃ the same route gives salicylic acid.

Drawn with 65 atoms, 10 arrows, 5 shapes – every one editable in MolDraw.

Sources

• Kürti & Czakó, Strategic Applications of Named Reactions in Organic Synthesis, Elsevier 2005 Textbook
• Smith, March's Advanced Organic Chemistry, 8th ed., Wiley 2020 Textbook