1. Chemical Structure and Properties
Molecular Formula: CH₆ClN
Structural Formula: CH₃NH₂·HCl
A primary amine hydrochloride obtained by neutralizing monomethylamine (MMA) with hydrochloric acid.
Physical Properties:
Appearance: White crystalline powder or hygroscopic solid.
Melting Point: 225–230°C (decomposes).
Solubility: Highly soluble in water (>600 g/L at 25°C), ethanol; insoluble in non-polar solvents.
Odor: Odorless (unlike volatile MMA gas).
Hygroscopicity: Absorbs moisture rapidly; requires airtight storage.
Chemical Properties:
Stability: Stable under dry conditions; decomposes upon heating to release MMA and HCl.
Reactivity: Weakly acidic (pKa ≈ 10.6); reacts with strong bases to regenerate free MMA.
2. Industrial Applications
Pharmaceuticals:
- Intermediate: Essential for synthesizing antihistamines (e.g., chlorpheniramine) and antidepressants (e.g., fluvoxamine).
- Salt Formation: Used to form stable, bioavailable salts (e.g., ephedrine hydrochloride).
Agrochemicals:
- Herbicide Precursor: Used in the synthesis of glyphosate and paraquat.
- Fungicide Intermediate: Key in dithiocarbamate compound production.
Organic Synthesis:
- Alkylation Reagent: Precursor for quaternary ammonium salts in surfactants (e.g., cocamidopropyl betaine).
- Catalyst: Facilitates Mannich-type reactions and peptide synthesis.
Textile Industry:
- Dye Fixative: Improves dye retention and washfastness in wool and silk.
3. Safety and Toxicology
Health Hazards:
- Potential liver and kidney effects (limited data); not classified as carcinogenic by IARC.
- Skin/Eye Contact: Causes irritation and possible burns (rabbit skin LD50: ~450 mg/kg).
- Inhalation: Dust or vapors may irritate the respiratory tract; treat as MMA hazard.
- Ingestion: Moderately toxic (oral LD50 rat: ~1,100 mg/kg); can cause GI irritation.
Handling Precautions:
- PPE: Wear nitrile gloves, chemical splash goggles, and N95 respirator when handling powder.
- Storage: Store in sealed containers in cool, dry, well-ventilated areas; avoid bases.
- First Aid: Rinse affected area with water; seek medical help for major exposures.
4. Environmental and Regulatory Compliance
Environmental Impact:
- Aquatic Toxicity: LC50 (fish, 96h): 80–150 mg/L; EC50 (daphnia): 40–80 mg/L.
- Biodegradability: Readily biodegradable (OECD 301D: >70% in 28 days).
- Persistence: Low due to rapid hydrolysis in water.
Regulatory Frameworks:
- GB 13690-2009: General Chemical classification; standard safety practices required.
- OSHA: No specific PEL; general duty clause applies.
- EPA: Listed under TSCA Inventory.
- CLP Regulation (EU): Skin Irrit. 2 (H315), Eye Irrit. 2 (H319), Acute Tox. 4 (H302).
- REACH: Fully registered with required SDS documentation.
Transport:
- UN Number: Not classified as hazardous; shipped as non-dangerous goods (non-DG).
5. Case Studies and Application Insights
Case 1: Glyphosate Synthesis
- Process: MMA HCl reacts with phosphorus trichloride and glycine to form glyphosate via Mannich condensation.
- Efficiency: 90% yield using 25% aqueous MMA HCl at 70°C (based on Bayer’s method).
Case 2: API Stabilization
- Application: Pfizer uses MMA HCl to prepare ephedrine hydrochloride, improving its solubility and shelf stability.
- Performance: Reduced active degradation by 40% under accelerated aging conditions.
Comparative Analysis:
- Pros: Solid form improves safety and ease of handling; non-flammable.
- Cons: Requires regeneration via basification to obtain free MMA for synthesis.