DIAZOMETHANE

Diazomethane
Diazomethane Diazomethane
Chemical name	Diazomethane
Chemical formula	CH2N2
Molecular mass	42.04 g/mol
Melting point	-145 °C
Boiling point	-23 °C
Density	1.4 (air=1)
CAS number	[334-88-3]
SMILES	C=[N+]=[N-]
Structure
Molecular shape	linear C=N=N
Dipole moment	polar
Hazards
MSDS	External MSDS
Main hazards	toxic and explosive
NFPA 704
Flash point	? °C
R/S statement for tmsCHN2	R: 12-19-22-66-67 S: 9-16-29-33
RTECS number	?
Supplementary data page
Structure and properties	''n'', εr, etc.
Thermodynamic data	Phase behaviour gas
Spectral data	UV, IR, NMR, MS
Related compounds
Related functional groups	R-N=N=N azide), R-N=N-R (azo)
Related compounds	R2CN2 R = Ph, tms, CF3
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

'Diazomethane' is the chemical compound CH₂N₂. In the pure form at room temperature, it is a yellow gas, but it is almost universally used as a solution in diethyl ether. It is one of the more common diazo compounds. It is also toxic and potentially explosive.
==Preparation^[1]==
CH₂N₂ is usually prepared as a solution in diethyl ether and used for converting carboxylic acids into their methyl esters or into their homologues (see Arndt-Eistert synthesis). In the 'Buchner-Curtius-Schlotterbeck reaction' (1885) diazomethane reacts with an aldehyde to form ketones. Diazomethane is also frequently used as a carbene equivalent. Diazomethane is prepared in the laboratory at mmol scale from precursors such as 'Diazald' or N-methyl-N-nitroso-p-toluenesulfonamide and 'MNNG' or 1-methyl-3-nitro-1-nitrosoguanidine. Diazald in a solution of diglyme and diethyl ether reacts with a warm aqueous solution of sodium hydroxide and the generated CH₂N₂ is collected by distillation. Diazomethane is liberated from a solution of MNNG in diethyl ether by addition of aqueous potassium hydroxide at low temperatures.

CH₂N₂ reacts with basic solutions of ²H₂O to give the deuterated derivative C²H₂N₂.^[2]

Contents

Assay

Other diazomethane compounds

Safety

References

External links

Assay

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 assayed using titration 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.

Other diazomethane compounds

Many substituted derivatives of diazomethane have been prepared:

★ The very stable (CF₃)₂CN₂ (b.p. 12–13 °C),^[3]

★ Ph₂CN₂ (m.p. 29–30 °C).^[4]

★ (CH₃)₃SiCHN₂, which is commercially available as a solution and is as effective as CH₂N₂ for methylation.^[5]

★ PhC(H)N₂, a red liquid b.p. < 25 °C at 0.1 mm Hg.^[6]

Safety

Diazomethane is toxic by inhalation or by contact with the skin or eyes (TLV 0.2ppm). Symptoms include chest discomfort, headache, weakness and, in severe cases, collapse.^[7] CH₂N₂ may explode when in contact with ground-glass joints or when heated to about 100.0 °C. Consequently specialized, scratch-free glassware and a blast shield should be employed for its use.

References

1.
J. A. Moore; D. E. Reed “Diazomethane” Organic Syntheses Collective Volume 5, page 351
2. P. G. Gassman and W. J. Greenlee “Dideuterodiazomethane” Organic Syntheses Collective Volume 6, page 432.
3. W. J. Middleton; D. M. Gale “Bis(Trifluoromethyl))diazomethane” Organic Syntheses Collective Volume 6, page 161
4. L. I. Smith, K. L. Howard “Diphenyldiazomethane” Organic Syntheses Collective Volume 3, page 351
5. T. Shioiri, T. Aoyama, S. Mori “Trimethylsilyldiazomethane” Organic Syntheses Collected Volume, Volume 8, page 612.
6. X. Creary “Tosylhydrazone Salt Pyrolyses: Phenydiazomethanes” Organic Syntheses, Coll. Vol. 7, p.438 (1990); Vol. 64, p.207 (1986).
7. Muir, GD (ed.) 1971, ''Hazards in the Chemical Laboratory'', The Royal Institute of Chemistry, London.

External links

★ MSDS diazomethane

★ Sigmaaldrich technical bulletin

★ The Buchner-Curtius-Schlotterbeck reaction @ Institute of Chemistry, Skopje, Macedonia

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