1. Chemical Structure and Properties

Molecular Formula: C₄H₁₂ClN

Structural Formula: (CH₂CH₃)₂NH·HCl

A secondary amine hydrochloride formed by neutralizing diethylamine (DEA) with hydrochloric acid.

Physical Properties:
 Appearance: White to off-white crystalline powder or hygroscopic solid.
 Melting Point: 223–227°C (decomposes).
 Solubility: Highly soluble in water (>600 g/L at 25°C), ethanol, and methanol; insoluble in non-polar solvents.
 Odor: Odorless (unlike volatile DEA gas).
 Hygroscopicity: Absorbs moisture rapidly; requires airtight storage.

Chemical Properties:
 Stability: Stable under dry conditions; decomposes upon heating to release DEA and HCl.
 Reactivity: Weakly acidic (pKa ≈ 10.9); regenerates DEA upon treatment with strong bases.

2. Industrial Applications

Pharmaceuticals:
 - Intermediate for local anesthetics (e.g., lidocaine) and antihistamines (e.g., diphenhydramine).
 - Salt Formation: Improves solubility and stability of APIs.

Agrochemicals:
 - Herbicide precursor: Key in atrazine and glyphosate production.
 - Fungicide intermediate: Utilized in triazole synthesis (e.g., propiconazole).

Organic Synthesis:
 - Reagent in alkylation, acylation, and Mannich-type reactions.
 - Surfactant precursor: Quaternary ammonium salt production for detergents and softeners.

Electronics:
 - Etching agent for silicon wafer processing in semiconductor fabrication.

3. Safety and Toxicology

Health Hazards:
 - Limited animal data suggests potential liver/kidney toxicity; not classified as carcinogenic (IARC).
 - Skin/Eye Contact: Irritating and corrosive (rabbit skin LD50: ~750 mg/kg).
 - Inhalation: Dust and vapors may irritate respiratory system; handle as DEA hazard.
 - Ingestion: Moderately toxic (oral LD50 rat: ~1,300 mg/kg); may cause gastrointestinal damage.

Handling Precautions:
 - PPE: Nitrile gloves, protective goggles, and N95 respirator for dust control.
 - Storage: Store in sealed, moisture-proof containers in cool, dry areas; avoid contact with alkalis.
 - First Aid: Rinse affected areas thoroughly with water; seek medical attention for serious exposure.

4. Environmental and Regulatory Compliance

Environmental Impact:
 - Aquatic Toxicity: LC50 (fish, 96h): 150–300 mg/L; EC50 (daphnia): 80–150 mg/L.
 - Biodegradability: Readily biodegradable (OECD 301D: >70% in 28 days).
 - Persistence: Degrades quickly via hydrolysis in aquatic environments.

Regulatory Frameworks:
 - GB 13690-2009 (China): Classified as General Chemical; standard safety measures required.
 - OSHA (US): No specific PEL; general duty clause applies.
 - EPA: Listed on TSCA Inventory.
 - CLP (EU): Classified as Skin Irrit. 2 (H315), Eye Irrit. 2 (H319), Acute Tox. 4 (H302).
 - REACH (EU): Registered with full SDS and handling documentation.

Transport:
 - UN Number: Not classified as hazardous for transport (non-DG).

5. Case Studies and Application Insights

Case 1: Lidocaine Synthesis
 - Process: DEA HCl reacts with 2,6-xylidine under catalytic acid to form lidocaine hydrochloride.
 - Efficiency: 88% yield at 60°C in optimized batch process (Pfizer).

Case 2: Atrazine Herbicide Production
 - Application: DEA HCl reacts with cyanuric chloride to form atrazine.
 - Performance: Yields >95% purity with controlled pH conditions (Syngenta process).

Comparative Analysis:
 - Pros: Solid form enhances handling safety; reduces flammability risks.
 - Cons: Requires regeneration via basification for certain synthetic steps.