Name: making methyl esters with diazomethane
Uploaded: 2025-05-22T09:05:37.000Z
Duration: 1 min 33 s
Channel: JoVE

Carboxylic acids, upon treatment with diazomethane, undergo alkylation to yield methyl esters.
Diazomethane, a yellow-colored gas generated from precursors such as N-methyl-N-nitrosourea and a base, is a resonance hybrid of three dipolar structures.
Mechanistically, diazomethane is protonated by carboxylic acid to generate a carboxylate anion and a methyldiazonium cation.
The methyldiazonium cation is an extremely unstable species bearing dinitrogen&#8211;an excellent leaving group.
Next, the nucleophilic carboxylate anion attacks the methyldiazonium cation via an SN2 mechanism to yield methyl esters with the simultaneous release of nitrogen gas.
Notice that the esterification proceeds via the nucleophilic carboxylate oxygen of the carboxylic acid. In contrast, acid-catalyzed Fischer esterification involves an electrophilic carbonyl carbon that eventually reacts with the nucleophilic alkoxy group of alcohol.
One of the applications of alkylation by diazomethane is to detect cocaine in a urine sample. Here, benzoylecgonine &#8211;a urinary metabolite of cocaine, is converted to a more suitable methyl ester to be detected by mass spectrometry analysis.

carboxylic acids to methylesters: alkylation using diazomethane

Carboxylic Acids to Methylesters: Alkylation using Diazomethane

Carboxylic acids react with diazomethane in an ether solvent via alkylation at the carboxylate oxygen atom to give methyl esters of the corresponding acid with excellent yields.
<img alt="Diazomethane reaction diagram showing ester formation from carboxylic acid with ether solvent." src="/files/ftp_upload/12349/12349_PT_Figure_1.svg" style="text-align: center; height: 60px;" data-altupdatedat="1754904545000" data-alt="Esterification reaction: carboxylic acid with diazomethane formula, chemical process diagram." />
Diazomethane is a yellow gas having a boiling point of &#8722;23 &#176;C. It is conveniently prepared by the action of a base on N-methyl-N-nitrosourea or N-methyl-N-nitrosotoluenesulphonamide.
The esterification mechanism involves the protonation of diazomethane by the carboxylic acid to yield a carboxylate salt and methyldiazonium cation. The methyldiazonium cation is highly unstable due to the presence of N&#8801;N, which functions as an excellent leaving group.
<img alt="Organic reaction mechanism diagram, arrow, molecular structures, chemical transformation analysis." src="/files/ftp_upload/12349/12349_PT_Figure_2.svg" style="text-align: center; height: 72px;" data-altupdatedat="1754904545000" data-alt="Chemical reaction, Curtius rearrangement equations, molecular transformation diagram." />
In the final alkylation step, an SN2 attack on the methyldiazonium ion by the carboxylate anion produces a methyl ester, along with the elimination of N2 gas.
<img alt="SN2 reaction diagram showing azide ion with carbonyl compound forming methyl ester and nitrogen gas." src="/files/ftp_upload/12349/12349_PT_Figure_3.svg" style="text-align: center; height: 70px;" data-altupdatedat="1754904545000" data-alt="SN2 reaction mechanism diagram; nucleophile attack on carbonyl, forming new bond, expelling N2." />
However, diazomethane is a potentially explosive gas and requires precautions during its handling and storage. It undergoes spontaneous detonation upon contact with rough or scratched surfaces. Therefore, flame-polished glassware and a blast shield are often recommended in reactions involving diazomethane. Moreover, diazomethane is highly toxic as well as carcinogenic.
Diazomethane decomposes in the presence of heat or light to generate carbenes and eliminate nitrogen.
<img alt="Diazoalkane decomposition; chemical equation, heat/light induced; nitrogen gas release." src="/files/ftp_upload/12349/12349_PT_Figure_4.svg" style="text-align: center; height: 52px;" data-altupdatedat="1754904545000" data-alt="Chemical reaction diagram; azide decomposition to form methylene and nitrogen under heat or light." />

Carboxylic acids react with diazomethane in an ether solvent&#160;via alkylation at the carboxylate oxygen atom&#160;to give&#160;methyl esters of the ...

carboxylic-acids-to-methylesters-alkylation-using-diazomethane

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Organic Chemistry

Unit 1

Carboxylic Acids

KEY TERMS AND CONCEPTS

making methyl esters with diazomethane

Carboxylic acids can be converted into methyl esters using diazomethane in an ether solvent. This reaction gives the methyl ester of the same acid and often does so in excellent yield. It is a useful esterification method in organic chemistry.

Diazomethane is a yellow gas with a boiling point of minus 23 degrees Celsius. It is commonly prepared by treating N-methyl-N-nitrosourea or N-methyl-N-nitrosotoluenesulphonamide with a base. During the reaction, the carboxylic acid first protonates diazomethane. This forms a carboxylate salt and a methyldiazonium cation.

The methyldiazonium cation is very unstable because it contains N≡N, which is an excellent leaving group. Next, the carboxylate anion attacks by an SN2 step. That step forms the methyl ester and releases nitrogen gas.

Diazomethane must be handled with great care. It is a potentially explosive gas and can detonate on rough or scratched surfaces. Flame-polished glassware and a blast shield are often used in reactions with diazomethane. It is also highly toxic and carcinogenic. Heat or light can break it down to form carbenes and nitrogen gas.

Making Methyl Esters with Diazomethane

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Carboxylic acids are named by IUPAC rules that focus on the carboxyl group, –COOH. For acyclic saturated monocarboxylic acids, the longest hydrocarbon chain that includes the –COOH carbon is chosen as the parent chain. The final -e in the parent hydrocarbon name is replaced with -oic acid, and numbering starts at the –COOH carbon. Substituents are then named and placed as prefixes in alphabetical order. In the presence of a carboxyl group, other groups such as –CHO, –CO–, –OH, –OR, –NH2, and...

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Carboxylic Acid Signals in NMR and MS

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Fischer esterification is an acid-catalyzed reaction that turns a carboxylic acid and an alcohol into an ester. This condensation reaction is a common way to make esters in organic chemistry. It also involves nucleophilic acyl substitution, which means one group is replaced on the acid carbonyl. The reaction proceeds through a tetrahedral intermediate. During this step, the molecule briefly has a tetrahedral shape before the reaction moves forward. Water is then eliminated as the leaving group.

Carboxylic acids can be converted into methyl esters using diazomethane in an ether solvent. This reaction gives the methyl ester of the same acid and often does so in excellent yield. It is a useful esterification method in organic chemistry. Diazomethane is a yellow gas with a boiling point of minus 23 degrees Celsius. It is commonly prepared by treating N-methyl-N-nitrosourea or N-methyl-N-nitrosotoluenesulphonamide with a base. During the reaction, the carboxylic acid first protonates...

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key terms and concepts

See how carboxylic acids react with diazomethane to form methyl esters, and learn the key SN2 mechanism and major safety concerns.

Making Methyl Esters with Diazomethane | JoVE K12

organic chemistry

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Making Methyl Esters with Diazomethane

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