Kolbe's reaction
Sodium phenoxide reacts with carbon dioxide at 400 K and 4 to 7 atm, and acidification gives salicylic acid.
PhenolC₆H₅OHPhenol - Step 1
(i) NaOH (ii) CO₂, 400 K, 4 to 7 atm (iii) H⁺
Salicylic acido-HOC₆H₄COOHCarboxylic acid
How it works
- Phenol is converted to sodium phenoxide with NaOH.
- The ring of the phenoxide attacks CO₂ (electrophilic substitution) at the ortho position.
- Acidification of sodium salicylate gives salicylic acid.
What it makes
Salicylic acid (and from it aspirin).
Where it fails
Mainly the ortho product forms. Do not confuse it with Kolbe electrolysis.
Class 12, Chapter 7 Alcohols, Phenols and Ethers
Kolbe's reaction: quick answers
What is the electrophile in Kolbe's reaction?
Carbon dioxide.
Why is the phenoxide used rather than phenol?
The phenoxide ion is much more reactive towards electrophiles than phenol.
How is aspirin made from the product?
Salicylic acid is acetylated with acetic anhydride.