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when Kolbe's reaction takes place , why the major product is o-hydoxy benzoic acid  [salicylic acid]instead of p-hydroxy benzoic acid when in general conditions para position provides better symetry  and stability?

The Kolbe-Schmitt reaction proceeds via the nucleophilic addition of a phenolate to carbon dioxide to give the salicylate. The final step is reaction of the salicylate with acid to form the desired salicylic acid.

The reason is that if you write down the mechanism and see, you will find that the intermediate formed is more stable when the negative charge is held in the ortho position, as you have an electron withdrawing oxygen atom present on the adjacent carbon atom. Kolbe's reaction depends on the stability of the intermediate formed, and as the ortho giving intermediate is more stable the final product is ortho.

 
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Kolbe-Schmitt Reaction

A base-promoted carboxylation of phenols that allows the synthesis of salicylic acid derivatives.

Mechanism of the Kolbe-Schmitt Reaction


this is the whole mechanism and that is why we get salicyclic acid instead of phydroxy benzoic acid

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SORRY IM ONLY CLASS 10 
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CLASS 10
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Kolbe's reaction, also known as Kolbe Schmitt Reaction is a type of addition reaction named after Hermann Kolbe and Rudolf Schmitt. When phenol is treated with sodium hydroxide, phenoxide ion is generated. The phenoxide ion generated is more reactive than phenol towards electrophilic aromatic substitution reaction. Hence, it undergoes electrophilic substitution reaction with carbon dioxide, which is a weak electrophile. Ortho-hydroxybenzoic acid (salicylic acid) is formed as the primary product. This reaction is popularly known as Kolbe’s reaction.
 
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The Kolbe-Schmitt reaction proceeds via the nucleophilic addition of a phenolate to carbon dioxide to give the salicylate. The final step is reaction of the salicylate with acid to form the desired salicylic acid.

The reason is that if you write down the mechanism and see, you will find that the intermediate formed is more stable when the negative charge is held in the ortho position, as you have an electron withdrawing oxygen atom present on the adjacent carbon atom. Kolbe's reaction depends on the stability of the intermediate formed, and as the ortho giving intermediate is more stable the final product is ortho.

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The mechanism for Kolbe's reaction is as follows:

 

From the above mechanism, the negative charge get developed on the ortho position. Hence the electrophillic substitution takes place at ortho position abd ortho hydroxy benzoic acid is formed as product.

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Kolbe's reaction, also known as Kolbe Schmitt Reaction is a type of addition reaction named after Hermann Kolbe and Rudolf Schmitt. When phenol is treated with sodium hydroxide, phenoxide ion is generated. The phenoxide ion generated is more reactive than phenol towards electrophilic aromatic substitution reaction. Hence, it undergoes electrophilic substitution reaction with carbon dioxide, which is a weak electrophile. Ortho-hydroxybenzoic acid (salicylic acid) is formed as the primary product. This reaction is popularly known as Kolbe’s reaction .
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