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Diazomethane
Diazomethane is an organic chemical compound with the formula CH2N2, discovered by German chemist Hans von Pechmann in 1894. It is the simplest diazo compound. In the pure form at room temperature, it is an extremely sensitive explosive yellow gas; thus, it is almost universally used as a solution in diethyl ether. The compound is a popular methylating agent in the laboratory, but it is too hazardous to be employed on an industrial scale without special precautions. Use of diazomethane has been significantly reduced by the introduction of the safer and equivalent reagent trimethylsilyldiazomethane.
For safety and convenience diazomethane is always prepared as needed as a solution in ether and used as such. It converts carboxylic acids to methyl esters and phenols into their methyl ethers. The reaction is thought to proceed via proton transfer from carboxylic acid to diazomethane to give a methyldiazonium cation, which reacts with the carboxylate ion to give the methyl ester and nitrogen gas. Labeling studies indicate that the initial proton transfer is faster than the methyl transfer step. Since proton transfer is required for the reaction to proceed, this reaction is selective for the more acidic carboxylic acids (pKa ~ 5) and phenols (pKa ~ 10) over aliphatic alcohols (pKa ~ 15).
In more specialized applications, diazomethane and other diazoalkyl reagents are used in the Arndt–Eistert reaction and the Büchner–Curtius–Schlotterbeck reaction for homologation of various compounds.
Diazomethane reacts with alcohols or phenols in presence of boron trifluoride (BF3) to give methyl ethers.
Diazomethane is also frequently used as a carbene source. It readily takes part in 1,3-dipolar cycloadditions.
A wide variety of routes have been developed for the laboratory production of diazomethane. In general, the synthesis of these all involves the addition of methylamine to an electron-deficient species, before treatment with nitrite and mineral acid (nitrous acid) to form an N-methyl nitrosamide. Diazomethane is prepared by hydrolysis of an ethereal solution of these N-methyl nitrosamides with aqueous base. Examples include:
Diazomethane reacts with alkaline solutions of D2O to give the deuterated derivative CD2N2. This can be used for isotopic labeling studies.
The ease with which diazomethane explodes makes it too hazardous to handle in large quantities. Despite this, it can be used on an industrial scale using on-demand flow chemistry. In these processes the rate of production is matched by the rate of consumption, such that the amount of diazomethane present at any one time is very low.
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Diazomethane
Diazomethane is an organic chemical compound with the formula CH2N2, discovered by German chemist Hans von Pechmann in 1894. It is the simplest diazo compound. In the pure form at room temperature, it is an extremely sensitive explosive yellow gas; thus, it is almost universally used as a solution in diethyl ether. The compound is a popular methylating agent in the laboratory, but it is too hazardous to be employed on an industrial scale without special precautions. Use of diazomethane has been significantly reduced by the introduction of the safer and equivalent reagent trimethylsilyldiazomethane.
For safety and convenience diazomethane is always prepared as needed as a solution in ether and used as such. It converts carboxylic acids to methyl esters and phenols into their methyl ethers. The reaction is thought to proceed via proton transfer from carboxylic acid to diazomethane to give a methyldiazonium cation, which reacts with the carboxylate ion to give the methyl ester and nitrogen gas. Labeling studies indicate that the initial proton transfer is faster than the methyl transfer step. Since proton transfer is required for the reaction to proceed, this reaction is selective for the more acidic carboxylic acids (pKa ~ 5) and phenols (pKa ~ 10) over aliphatic alcohols (pKa ~ 15).
In more specialized applications, diazomethane and other diazoalkyl reagents are used in the Arndt–Eistert reaction and the Büchner–Curtius–Schlotterbeck reaction for homologation of various compounds.
Diazomethane reacts with alcohols or phenols in presence of boron trifluoride (BF3) to give methyl ethers.
Diazomethane is also frequently used as a carbene source. It readily takes part in 1,3-dipolar cycloadditions.
A wide variety of routes have been developed for the laboratory production of diazomethane. In general, the synthesis of these all involves the addition of methylamine to an electron-deficient species, before treatment with nitrite and mineral acid (nitrous acid) to form an N-methyl nitrosamide. Diazomethane is prepared by hydrolysis of an ethereal solution of these N-methyl nitrosamides with aqueous base. Examples include:
Diazomethane reacts with alkaline solutions of D2O to give the deuterated derivative CD2N2. This can be used for isotopic labeling studies.
The ease with which diazomethane explodes makes it too hazardous to handle in large quantities. Despite this, it can be used on an industrial scale using on-demand flow chemistry. In these processes the rate of production is matched by the rate of consumption, such that the amount of diazomethane present at any one time is very low.