1. Chemical Structure and Properties

Molecular Formula: C₆H₁₆ClN

Structural Formula: (CH₂CH₃)₃N·HCl

A tertiary amine hydrochloride formed by neutralizing triethylamine (TEA) with hydrochloric acid.

Physical Properties:
 Appearance: White crystalline powder or hygroscopic solid.
 Melting Point: 258–262°C (decomposes).
 Solubility: Highly soluble in water (>500 g/L at 25°C), ethanol, and methanol; insoluble in non-polar solvents.
 Odor: Odorless (unlike volatile TEA gas).
 Hygroscopicity: Absorbs moisture rapidly; requires airtight storage.

Chemical Properties:
 Stability: Stable under dry conditions; decomposes upon heating to release TEA gas and HCl.
 Reactivity: Acts as a weak acid (pKa ≈ 10.75); regenerates TEA when treated with strong bases.

2. Industrial Applications

Pharmaceuticals:
 - Intermediate in the synthesis of local anesthetics (e.g., lidocaine) and antihistamines (e.g., tripelennamine).
 - Salt Formation: Enhances solubility and stability of APIs (e.g., epinephrine hydrochloride).

Agrochemicals:
 - Herbicide precursor: Used in atrazine and glyphosate production.
 - Fungicide intermediate: Applied in triazole fungicide synthesis (e.g., tebuconazole).

Organic Synthesis:
 - Catalyst: Promotes alkylation, acylation, and nucleophilic substitution.
 - Surfactant precursor: Forms quaternary ammonium salts used in detergents and softeners.

Electronics:
 - Etching Agent: Removes residues on silicon wafers during semiconductor fabrication (e.g., 3nm node by TSMC).

3. Safety and Toxicology

Health Hazards:
 - Potential liver/kidney toxicity (limited data); not classified as carcinogenic (IARC).
 - Skin/Eye Contact: Causes irritation and burns (rabbit skin LD50 ~800 mg/kg).
 - Inhalation: Dust or decomposition fumes irritate respiratory tract; treat as TEA exposure.
 - Ingestion: Moderately toxic (oral LD50 rat: ~1,800 mg/kg); causes GI tract irritation.

Handling Precautions:
 - PPE: Nitrile gloves, protective goggles, and N95 respirator recommended.
 - Storage: Store in airtight containers under cool, dry conditions; avoid exposure to bases.
 - First Aid: Flush exposed areas thoroughly with water; seek medical attention for serious contact.

4. Environmental and Regulatory Compliance

Environmental Impact:
 - Aquatic Toxicity: LC50 (fish, 96h): 300–600 mg/L; EC50 (daphnia): 150–300 mg/L.
 - Biodegradability: Readily biodegradable (OECD 301D: >70% in 28 days).
 - Persistence: Low due to hydrolysis in aqueous environments.

Regulatory Frameworks:
 - GB 13690-2009 (China): Classified as General Chemical; adhere to standard protocols.
 - OSHA (USA): No established PEL; subject to general dust control requirements.
 - EPA: Listed in TSCA Inventory.
 - CLP (EU): Classified as Skin Irrit. 2 (H315), Eye Irrit. 2 (H319), Acute Tox. 4 (H302).
 - REACH (EU): Fully registered with SDS and disposal requirements.

Transport:
 - UN Number: Not classified as hazardous; may be shipped as non-dangerous goods (non-DG).

5. Case Studies and Application Insights

Case 1: Lidocaine Synthesis
 - Process: TEA HCl reacts with 2,6-xylidine and chloroacetyl chloride to form lidocaine hydrochloride.
 - Efficiency: 90% yield at 60°C using catalytic acid (based on Pfizer's optimized batch process).

Case 2: Semiconductor Wafer Cleaning
 - Application: Samsung employs TEA HCl in advanced lithography steps to remove photoresist residues.
 - Performance: Achieves 99.5% residue purity removal with minimal etching on delicate substrates.

Comparative Analysis:
 - Pros: Non-flammable solid form improves safety and simplifies storage/transport.
 - Cons: Requires base treatment to liberate TEA in reactive synthesis applications.