Diazomethane

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Diazomethane
Diazomethane
Diazomethane
Names
IUPAC name
Diazomethane
Other names
Azimethylene,
Azomethylene,
Identifiers
3D model (
JSmol
)
ChEBI
ChemSpider
ECHA InfoCard
 100.005.803 Edit this at Wikidata
EC Number
  • 206-382-7
KEGG
UNII
  • InChI=1S/CH2N2/c1-3-2/h1H2 checkY
    Key: YXHKONLOYHBTNS-UHFFFAOYSA-N checkY
  • InChI=1/CH2N2/c1-3-2/h1H2
    Key: YXHKONLOYHBTNS-UHFFFAOYAZ
  • N#[N+]-[C-]
Properties
CH2N2
Molar mass 42.04 g/mol
Appearance Yellow 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:
GHS01: ExplosiveGHS08: Health hazard
Danger
H350
P201, P202, P281, P308+P313, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 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)[3]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 0.2 ppm (0.4 mg/m3)[2]
REL (Recommended)
 TWA 0.2 ppm (0.4 mg/m3)[2]
IDLH
(Immediate danger)
 2 ppm[2]
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).
☒N verify (what is checkY☒N ?)

Diazomethane is an organic chemical compound with the formula CH2N2, discovered by German chemist

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]

Use

For safety and convenience diazomethane is always prepared as needed as a solution in

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]

In more specialized applications, diazomethane and

Büchner–Curtius–Schlotterbeck reaction for homologation.[8][9]

Büchner-Curtius-Schlotterbeck Reaction.

Diazomethane reacts with

methyl ethers
.

Diazomethane is also frequently used as a

1,3-dipolar cycloadditions
.


Preparation

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.

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

extinction coefficient, ε, is 7.2.[citation needed
] The gas-phase concentration of diazomethane can be determined using photoacoustic spectroscopy.[4]

Related compounds

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.

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]


References

  1. ^ ICSC 1256 – DIAZOMETHANE
  2. ^ a b c NIOSH Pocket Guide to Chemical Hazards. "#0182". National Institute for Occupational Safety and Health (NIOSH).
  3. ^ "Diazomethane". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  4. ^
    doi:10.1021/op020049k
    .
  5. ISBN 0471936235
    .
  6. doi:10.1016/S0040-4039(01)89341-2
    .
  7. OCLC 761379371
    .
  8. doi:10.1002/cber.188501802118
    .
  9. doi:10.1002/cber.19070400179
    .
  10. ^ "Synthese und Stoffwissen". organic-btc-ilmenaus Webseite! (in German). Retrieved 2020-11-02.
  11. 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. doi:10.15227/orgsyn.036.0016
    .
  20. ISBN 9783527652914
    .
  21. ISSN 0021-9584
    .
  22. ISSN 0021-9584
    .
  23. OCLC 213375246.{{cite book}}: CS1 maint: others (link
    )

External links

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