Ch_322b_21.04

Ch_322b_21.04 - salicyclic acid with acetic anhydride: : O...

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Carboxylation of the Phenoxide Ion: The Kolbe Reaction The discovery by Herman Kolbe (1818-1884) of the carboxylation of sodium phenoxide in 1859 was an important step towards a general synthesis of salicylic acid and, eventually, aspirin (O-acetylsalicylic acid). The Kolbe Reaction O - Na + CO 2 , 4-7 atm 125 o C OH CO 2 - Na + sodium salicylate major product H 3 O + OH COOH salicylic acid The ortho isomer is easily recovered from the para by steam distillation separation. The ortho isomer steam distills while the para does not.
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the carboxylation step ~H + tautomerization (rearomatization) The Synthesis of Aspirin (O-Acetylsalicylic Acid) Aspirin is prepared on large scale by the reaction of
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Unformatted text preview: salicyclic acid with acetic anhydride: : O : = H C-Na + O . . . . . . O . . . . OH Na + C-O . . . . . . O . . . . sodium salicylate : O :-Na + C O O The phenoxide acts as a nucleophile by way of the ortho carbon. A small amount of para addition occurs. . . OH COOH salicylic acid + CH 3 COCCH 3 O acetic anhydride H + O OCCH 3 COOH + CH 3 COH aspirin O O CH 3 OH CH 3 OH COOH Quiz 21.04 Provide the missing structures in the scheme below. CH 3 NH 2 (i) NaNO 2 , HBr, H 2 O, 0 o C (ii) Cu 2 O, Cu(NO 3 ) 2 , H 2 O (ii) CO 2 ,pressure, heat (iii) H 3 O + (i) KOH...
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This note was uploaded on 10/20/2009 for the course CHEM 322BL at USC.

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Ch_322b_21.04 - salicyclic acid with acetic anhydride: : O...

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