Diazomethane

Last updated
Diazomethane
Diazomethane-resonance-structures-2D.png
Diazomethane-from-CRC-MW-IR-3D-vdW.png
Names
IUPAC name
Diazomethane
Other names
Azimethylene,
Azomethylene,
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.005.803 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 206-382-7
KEGG
PubChem CID
UNII
  • InChI=1S/CH2N2/c1-3-2/h1H2 Yes check.svgY
    Key: YXHKONLOYHBTNS-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/CH2N2/c1-3-2/h1H2
    Key: YXHKONLOYHBTNS-UHFFFAOYAZ
  • N≡N:N#[N+]-[C-]
  • N=N:[N-]=[N+]=[C]
Properties
CH2N2
Molar mass 42.04 g/mol
AppearanceYellow gas
Odor musty
Density 1.4 (air=1)
Melting point −145 °C (−229 °F; 128 K)
Boiling point −23 °C (−9 °F; 250 K)
hydrolysis [1]
Structure
linear C=N=N
polar
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
toxic and explosive
GHS labelling:
GHS-pictogram-explos.svg GHS-pictogram-silhouette.svg
Danger
H350
P201, P202, P281, P308+P313, P405, P501
NFPA 704 (fire diamond)
NFPA 704.svgHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g. gasolineInstability 4: Readily capable of detonation or explosive decomposition at normal temperatures and pressures. E.g. nitroglycerinSpecial hazards (white): no code
4
3
4
Lethal dose or concentration (LD, LC):
175 ppm (cat, 10 min) [2]
NIOSH (US health exposure limits):
PEL (Permissible)
TWA 0.2 ppm (0.4 mg/m3) [3]
REL (Recommended)
TWA 0.2 ppm (0.4 mg/m3) [3]
IDLH (Immediate danger)
2 ppm [3]
Related compounds
Related functional groups;
compounds
R-N=N=N (azide),
R-N=N-R (azo);
R2CN2 R = Ph, tms, CF3
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

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. [4] Use of diazomethane has been significantly reduced by the introduction of the safer and equivalent reagent trimethylsilyldiazomethane. [5]

Contents

Use

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 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. [6] 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). [7]

Diazomethanemethylation.png

In more specialized applications, diazomethane and homologues are used in Arndt-Eistert synthesis and the Büchner–Curtius–Schlotterbeck reaction for homologation. [8] [9]

Buchner-Curtius-Schlotterbeck Reaction. Buchner-Curtius-Schlotterbeck Reaction.svg
Büchner-Curtius-Schlotterbeck Reaction.

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.


Preparation

Diazomethane laboratory preparation Diazomethane preparation - Macro Diazald Kit.jpg
Diazomethane laboratory preparation

Diazomethane is prepared by hydrolysis of an ethereal solution of an N-methyl nitrosamide with aqueous base. The traditional precursor is N-nitroso-N-methylurea, but this compound is itself somewhat unstable, and nowadays compounds such as N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and N-methyl-N-nitroso-p-toluenesulfonamide (Diazald) [10] are preferred. [11]

Common routes for the preparation of diazomethane. Diazomethane Synthesis V.1.png
Common routes for the preparation of diazomethane.

CH2N2 reacts with basic solutions of D2O to give the deuterated derivative CD2N2. [12]

The concentration of CH2N2 can be determined in either of two convenient ways. It can be treated with an excess of benzoic acid in cold Et2O. Unreacted benzoic acid is then back-titrated with standard NaOH. Alternatively, the concentration of CH2N2 in Et2O can be determined spectrophotometrically at 410 nm where its extinction coefficient, ε, is 7.2.[ citation needed ] The gas-phase concentration of diazomethane can be determined using photoacoustic spectroscopy. [4]

Diazomethane is both isomeric and isoelectronic with the more stable cyanamide, but they cannot interconvert. Many substituted derivatives of diazomethane have been prepared:

Safety

Diazomethane is toxic by inhalation or by contact with the skin or eyes (TLV 0.2 ppm). Symptoms include chest discomfort, headache, weakness and, in severe cases, collapse. [17] Symptoms may be delayed. Deaths from diazomethane poisoning have been reported. In one instance a laboratory worker consumed a hamburger near a fumehood where he was generating a large quantity of diazomethane, and died four days later from fulminating pneumonia. [18] Like any other alkylating agent it is expected to be carcinogenic, but such concerns are overshadowed by its serious acute toxicity.

CH2N2 may explode in contact with sharp edges, such as ground-glass joints, even scratches in glassware. [19] Glassware should be inspected before use and preparation should take place behind a blast shield. Specialized kits to prepare diazomethane with flame-polished joints are commercially available.

The compound explodes when heated beyond 100 °C, exposed to intense light, alkali metals, or calcium sulfate. Use of a blast shield is highly recommended while using this compound.

Proof-of-concept work has been done with microfluidics, in which continuous point-of-use synthesis from N-methyl-N-nitrosourea and 0.93 M potassium hydroxide in water was followed by point-of-use conversion with benzoic acid, resulting in a 65% yield of the methyl benzoate ester within seconds at temperatures ranging from 0 to 50 °C. The yield was better than under capillary conditions; the microfluidics were credited with "suppression of hot spots, low holdup, isothermal conditions, and intensive mixing." [20]

Isomers

The stable compound cyanamide, whose minor tautomer is carbodiimide, is an isomer of diazomethane. Less stable but still isolable isomers of diazomethane include the cyclic 3H-diazirine and isocyanoamine (isodiazomethane). [21] [22] In addition, the parent nitrilimine has been observed under matrix isolation conditions. [23]

Diazomethaneisomers.png


Related Research Articles

<span class="mw-page-title-main">Benzoic acid</span> Organic compound (C6H5COOH)

Benzoic acid is a white solid organic compound with the formula C6H5COOH, whose structure consists of a benzene ring with a carboxyl substituent. The benzoyl group is often abbreviated "Bz", thus benzoic acid is also denoted as BzOH, since the benzoyl group has the formula –C6H5CO. It is the simplest aromatic carboxylic acid. The name is derived from gum benzoin, which was for a long time its only source.

<span class="mw-page-title-main">Carboxylic acid</span> Organic compound containing a –C(=O)OH group

In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group attached to an R-group. The general formula of a carboxylic acid is often written as R−COOH or R−CO2H, sometimes as R−C(O)OH with R referring to an organyl group, or hydrogen, or other groups. Carboxylic acids occur widely. Important examples include the amino acids and fatty acids. Deprotonation of a carboxylic acid gives a carboxylate anion.

<span class="mw-page-title-main">Ester</span> Compound derived from an acid

In chemistry, an ester is a compound derived from an acid in which the hydrogen atom (H) of at least one acidic hydroxyl group of that acid is replaced by an organyl group. Analogues derived from oxygen replaced by other chalcogens belong to the ester category as well. According to some authors, organyl derivatives of acidic hydrogen of other acids are esters as well, but not according to the IUPAC.

Demethylation is the chemical process resulting in the removal of a methyl group (CH3) from a molecule. A common way of demethylation is the replacement of a methyl group by a hydrogen atom, resulting in a net loss of one carbon and two hydrogen atoms.

Chromic acid is jargon for a solution formed by the addition of sulfuric acid to aqueous solutions of dichromate. It consists at least in part of chromium trioxide.

<span class="mw-page-title-main">Phthalic anhydride</span> Chemical compound

Phthalic anhydride is the organic compound with the formula C6H4(CO)2O. It is the anhydride of phthalic acid. Phthalic anhydride is a principal commercial form of phthalic acid. It was the first anhydride of a dicarboxylic acid to be used commercially. This white solid is an important industrial chemical, especially for the large-scale production of plasticizers for plastics. In 2000, the worldwide production volume was estimated to be about 3 million tonnes per year.

<span class="mw-page-title-main">Alkylation</span> Transfer of an alkyl group from one molecule to another

Alkylation is a chemical reaction that entails transfer of an alkyl group. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene. Alkylating agents are reagents for effecting alkylation. Alkyl groups can also be removed in a process known as dealkylation. Alkylating agents are often classified according to their nucleophilic or electrophilic character. In oil refining contexts, alkylation refers to a particular alkylation of isobutane with olefins. For upgrading of petroleum, alkylation produces a premium blending stock for gasoline. In medicine, alkylation of DNA is used in chemotherapy to damage the DNA of cancer cells. Alkylation is accomplished with the class of drugs called alkylating antineoplastic agents.

In organic chemistry, the diazo group is an organic moiety consisting of two linked nitrogen atoms at the terminal position. Overall charge-neutral organic compounds containing the diazo group bound to a carbon atom are called diazo compounds or diazoalkanes and are described by the general structural formula R2C=N+=N−. The simplest example of a diazo compound is diazomethane, CH2N2. Diazo compounds should not be confused with azo compounds or with diazonium compounds.

<span class="mw-page-title-main">Diisopropyl ether</span> Chemical compound

Diisopropyl ether is a secondary ether that is used as a solvent. It is a colorless liquid that is slightly soluble in water, but miscible with organic solvents. It is used as an extractant and an oxygenate gasoline additive. It is obtained industrially as a byproduct in the production of isopropanol by hydration of propylene. Diisopropyl ether is sometimes represented by the abbreviation DIPE.

<span class="mw-page-title-main">Oxalyl chloride</span> Chemical compound

Oxalyl chloride is an organic chemical compound with the formula Cl−C(=O)−C(=O)−Cl. This colorless, sharp-smelling liquid, the diacyl chloride of oxalic acid, is a useful reagent in organic synthesis.

In organic chemistry, ozonolysis is an organic reaction where the unsaturated bonds are cleaved with ozone. Multiple carbon–carbon bond are replaced by carbonyl groups, such as aldehydes, ketones, and carboxylic acids. The reaction is predominantly applied to alkenes, but alkynes and azo compounds are also susceptible to cleavage. The outcome of the reaction depends on the type of multiple bond being oxidized and the work-up conditions.

In organic chemistry, the Arndt–Eistert reaction is the conversion of a carboxylic acid to its homologue. Named for the German chemists Fritz Arndt (1885–1969) and Bernd Eistert (1902–1978), the method entails treating an acid chlorides with diazomethane. It is a popular method of producing β-amino acids from α-amino acids.

<span class="mw-page-title-main">Trimethylsilyldiazomethane</span> Chemical compound

Trimethylsilyldiazomethane is the organosilicon compound with the formula (CH3)3SiCHN2. It is classified as a diazo compound. Trimethylsilyldiazomethane is a commercially available reagent used in organic chemistry as a methylating agent and as a source of CH2 group. Its behavior is akin to the less convenient reagent diazomethane.

<span class="mw-page-title-main">Thiophenol</span> Chemical compound

Thiophenol is an organosulfur compound with the formula C6H5SH, sometimes abbreviated as PhSH. This foul-smelling colorless liquid is the simplest aromatic thiol. The chemical structures of thiophenol and its derivatives are analogous to phenols. An exception is the oxygen atom in the hydroxyl group (-OH) bonded to the aromatic ring is replaced by a sulfur atom. The prefix thio- implies a sulfur-containing compound and when used before a root word name for a compound which would normally contain an oxygen atom, in the case of 'thiol' that the alcohol oxygen atom is replaced by a sulfur atom.

Benzyl chloride, or α-chlorotoluene, is an organic compound with the formula C6H5CH2Cl. This colorless liquid is a reactive organochlorine compound that is a widely used chemical building block.

The Blaise ketone synthesis is the chemical reaction of acid chlorides with organozinc compounds to give ketones.

<span class="mw-page-title-main">Dimethoxymethane</span> Chemical compound

Dimethoxymethane, also called methylal, is a colorless flammable liquid with a low boiling point, low viscosity and excellent dissolving power. It has a chloroform-like odor and a pungent taste. It is the dimethyl acetal of formaldehyde. Dimethoxymethane is soluble in three parts water and miscible with most common organic solvents.

<span class="mw-page-title-main">Cyclopropanation</span> Chemical process which generates cyclopropane rings

In organic chemistry, cyclopropanation refers to any chemical process which generates cyclopropane rings. It is an important process in modern chemistry as many useful compounds bear this motif; for example pyrethroid insecticides and a number of quinolone antibiotics. However, the high ring strain present in cyclopropanes makes them challenging to produce and generally requires the use of highly reactive species, such as carbenes, ylids and carbanions. Many of the reactions proceed in a cheletropic manner.

<span class="mw-page-title-main">Lead(IV) acetate</span> Organometallic compound (Pb(C2H3O2)4)

Lead(IV) acetate or lead tetraacetate is an metalorganic compound with chemical formula Pb(C2H3O2)4. It is a colorless solid that is soluble in nonpolar, organic solvents, indicating that it is not a salt. It is degraded by moisture and is typically stored with additional acetic acid. The compound is used in organic synthesis.

The Buchner–Curtius–Schlotterbeck reaction is the reaction of aldehydes or ketones with aliphatic diazoalkanes to form homologated ketones. It was first described by Eduard Buchner and Theodor Curtius in 1885 and later by Fritz Schlotterbeck in 1907. Two German chemists also preceded Schlotterbeck in discovery of the reaction, Hans von Pechmann in 1895 and Viktor Meyer in 1905. The reaction has since been extended to the synthesis of β-keto esters from the condensation between aldehydes and diazo esters. The general reaction scheme is as follows:

References

  1. ↑ ICSC 1256 – DIAZOMETHANE
  2. ↑ "Diazomethane". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  3. 1 2 3 NIOSH Pocket Guide to Chemical Hazards. "#0182". National Institute for Occupational Safety and Health (NIOSH).
  4. 1 2 Proctor, Lee D.; Warr, Antony J. (November 2002). "Development of a Continuous Process for the Industrial Generation of Diazomethane". Organic Process Research & Development. 6 (6): 884–892. doi:10.1021/op020049k.
  5. ↑ Shioiri, Takayuki; Aoyama, Toyohiko; Snowden, Timothy (2001). "Trimethylsilyldiazomethane". Encyclopedia of Reagents for Organic Synthesis. e-EROS Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rt298.pub2. ISBN   0471936235.
  6. ↑ van der Merwe, K.J.; Steyn, P.S.; Eggers, S.H. (January 1964). "A simple preparation of deuterium labelled O-methyl groups for mass spectrometry". Tetrahedron Letters. 5 (52): 3923–3925. doi:10.1016/S0040-4039(01)89341-2.
  7. ↑ Clayden, Jonathan. (2012). Organic chemistry. Greeves, Nick., Warren, Stuart G. (2nd ed.). Oxford: Oxford University Press. ISBN   978-0-19-927029-3. OCLC   761379371.
  8. ↑ Buchner, E.; Curtius, Th. (1885). "Synthese von Ketonsäureäthern aus Aldehyden und Diazoessigäther". Berichte der Deutschen Chemischen Gesellschaft. 18 (2): 2371–2377. doi:10.1002/cber.188501802118.
  9. ↑ Schlotterbeck, F. (1907). "The conversion of aldehydes and ketones through diazomethane". Berichte der Deutschen Chemischen Gesellschaft. 40: 479–483. doi:10.1002/cber.19070400179.
  10. ↑ "Synthese und Stoffwissen". organic-btc-ilmenaus Webseite! (in German). Retrieved 2020-11-02.
  11. ↑ Reed, Donald E.; James A. Moore (1961). "DIAZOMETHANE". Organic Syntheses. 41: 16. doi:10.15227/orgsyn.041.0016.
  12. ↑ P. G. Gassman & W. J. Greenlee (1988). "Dideuterodiazomethane". Organic Syntheses ; Collected Volumes, vol. 6, p. 432.
  13. ↑ W. J. Middleton; D. M. Gale (1988). "Bis(Trifluoromethyl)diazomethane". Organic Syntheses ; Collected Volumes, vol. 6, p. 161.
  14. ↑ L. I. Smith; K. L. Howard (1955). "Diphenyldiazomethane"". Organic Syntheses ; Collected Volumes, vol. 3, p. 351.
  15. ↑ T. Shioiri; T. Aoyama; S. Mori. "Trimethylsilyldiazomethane". Organic Syntheses ; Collected Volumes, vol. 8, p. 612.
  16. ↑ X. Creary (1990). "Tosylhydrazone Salt Pyrolyses: Phenydiazomethanes". Organic Syntheses ; Collected Volumes, vol. 7, p. 438.
  17. ↑ Muir, GD (ed.) 1971, Hazards in the Chemical Laboratory, The Royal Institute of Chemistry, London.
  18. ↑ LeWinn, E.B. "Diazomethane Poisoning: Report of a fatal case with autopsy", The American Journal of the Medical Sciences, 1949, 218, 556-562.
  19. ↑ de Boer, Th. J.; Backer, H. J. (1956). "DIAZOMETHANE". Organic Syntheses. 36: 16. doi:10.15227/orgsyn.036.0016.
  20. ↑ Wladimir Reschetilowski (2013-09-13). Microreactors in Preparative Chemistry: Practical Aspects in Bioprocessing, Nanotechnology, Catalysis and more. Wiley. p. 6–15. ISBN   9783527652914.
  21. ↑ Anselme, J.-P. (1977-05-01). "Isodiazomethane revisited. N-aminoisonitriles". Journal of Chemical Education. 54 (5): 296. Bibcode:1977JChEd..54..296A. doi:10.1021/ed054p296. ISSN   0021-9584.
  22. ↑ Anselme, J. P. (1966-11-01). "The chemistry of isodiazomethane". Journal of Chemical Education. 43 (11): 596. Bibcode:1966JChEd..43..596A. doi:10.1021/ed043p596. ISSN   0021-9584.
  23. ↑ Comprehensive organic functional group transformations II. Katritzky, Alan R., Taylor, Richard J. K. (1st ed.). Amsterdam: Elsevier. 2005. ISBN   9780080523477. OCLC   213375246.{{cite book}}: CS1 maint: others (link)
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