Esterification using Diazomethane The addition of an ethereal solution of diazomethane smoothly converts carboxylic acids to their methyl esters. CH2N2-R-C-O-CH3 0 R-C-OH The only by-product is nitrogen gas E.g. CO3H CH2N2 CO2CH3 +N2 Diazomethane is a toxic,explosive yellow gas that dissolves in ether,and requires special glassware. The mechanism involves the deprotonation of the hydroxyl oxygen,which generates a methyldiazonium salt, which is a potent methylating agent. Step 1:Proton transfer,forming a carboxylate ion and a methyldiazonium ion. CH,-N-N: o R-C-与HL:CH,-N=N R-C-0:+CH-N=N: carboxylate ion methyldiazonium ion Ch20 Carboxylic Acids (landscape) Page 26 Ch20 Carboxylic Acids (landscape) Page 26 Esterification using Diazomethane The addition of an ethereal solution of diazomethane smoothly converts carboxylic acids to their methyl esters. The only by-product is nitrogen gas. E.g. Diazomethane is a toxic, explosive yellow gas that dissolves in ether, and requires special glassware. The mechanism involves the deprotonation of the hydroxyl oxygen, which generates a methyldiazonium salt, which is a potent methylating agent. R C O OH R C O O-CH3 CH2N2 CO2H CH2N2 CO2CH3 + N2