Diazomethane (CH₂N₂) is the simplest diazo compound. In its pure form at room temperature, it is an extremely explosive yellow gas. Even solutions containing concentrated diazomethane can detonate violently.
It has a musty odour, is soluble in ether and dioxane, and decomposes slowly in these solvents. The presence of water or alcohols accelerates decomposition.
What is Diazomethane used for?
Diazomethane is primarily used in laboratories as a methylating agent for acidic compounds such as carboxylic acids, phenols, and enols.
Diazomethane is primarily used in laboratories as a methylating agent for acidic compounds such as carboxylic acids, phenols, and enols—facilitating the formation of methyl esters and ethers in organic synthesis.
Environmental Effects
Diazomethane may be released to the environment through waste streams during its production or laboratory use.
In air, diazomethane exists only as a gas, where it undergoes rapid hydrolysis with atmospheric moisture.
It can also degrade by reaction with hydroxyl radicals in the atmosphere, with an estimated half-life of 16 days.
Due to its rapid breakdown, diazomethane does not persist in water or soil, and bioaccumulation and biodegradation are not expected.
Sources & Routes of Exposure
Sources of Exposure
Occupational: inhalation during laboratory synthesis or when using gas supplied in its pure form.
Dermal contact: exposure to solutions of diazomethane in organic solvents.
General population: exposure is unlikely, as diazomethane is almost exclusively used in controlled laboratory settings.
Routes of Exposure
Inhalation: the primary route, causing respiratory damage.
Skin/eye contact: can cause severe irritation or systemic effects.
Ingestion: though unlikely, may also cause harmful effects.
Animal studies show severe outcomes such as haemorrhagic emphysema, pulmonary oedema, and bronchopneumonia.
Acute inhalation tests in cats confirm high acute toxicity.
Chronic Effects
No human or animal data available.
No EPA Reference Concentration (RfC) or Reference Dose (RfD) established.
Reproductive/Developmental Effects
No data available in humans or animals.
Cancer Risk
No human studies available.
Animal studies: increased pulmonary adenomas in rats and mice (inhalation) and in dermally exposed mice.
EPA: no classification for carcinogenicity.
IARC: Group 3 — not classifiable as to human carcinogenicity.
Safety
First Aid Measures
Inhalation: Move the person to fresh air immediately. If not breathing, administer artificial respiration. Seek medical attention urgently.
Skin contact: Wash thoroughly with soap and water. Seek medical advice if irritation or symptoms develop.
Eye contact: Rinse cautiously with plenty of water for at least 15 minutes. Seek medical attention immediately.
Ingestion: Do not give anything by mouth to an unconscious person. Rinse mouth with water and consult a physician immediately.
Exposure Controls and Personal Protection
Engineering Controls
Always handle diazomethane with adequate ventilation in fume hoods or closed systems.
Follow strict laboratory hygiene practices: wash hands thoroughly after handling and before breaks.
Ensure procedures minimise the risk of leaks, vapour build-up, or direct contact.
Personal Protective Equipment
Eye/face protection: Safety glasses with side shields or goggles plus a face shield (NIOSH/EN-approved).
Skin protection: Chemical-resistant gloves compliant with EN 374 standards. Inspect before use and follow proper glove removal techniques to prevent contamination. Wash and dry hands thoroughly after handling.
Body protection: Full chemical protective clothing, selected according to concentration and risk at the workplace.
Respiratory protection:
For routine handling: a full-face particle respirator (N100 in the US, P3 in the EU) as backup to engineering controls.
For high-risk scenarios: a full-face supplied-air respirator. Respirators and filters must meet NIOSH (US) or CEN (EU) standards.
Regulation
United States
OSHA: The Occupational Safety & Health Administration has set the following Permissible Exposure Limit (PEL) for diazomethane:
General Industry: 0.2 ppm, 0.4 mg/m3
Construction Industry: 0.2 ppm, 0.4 mg/m3 TWA
ACGIH: The American Conference of Governmental Industrial Hygienists has set a Threshold Limit Value (TLV) for diazomethane of 0.2 ppm, 0.34 mg/m3 TWA; Appendix A2 (Suspected Human Carcinogen)
NIOSH: The National Institute for Occupational Safety and Health has set a Recommended Exposure Limit (REL) for diazomethane of 0.2 ppm TWA
Australia
Safe Work Australia: Safe Work Australia has established an 8-hour Time Weighted Average (TWA) concentration for diazomethane of 0.2ppm; 0.34mg/m3. It has also been classified Carcinogenicity Category 1B, which means that it is presumed to have a carcinogenic potential for humans.
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