Didecyl Dimethyl Ammonium Chloride, Didecyldimonium Chloride, DDAC, 7173-51-5

Didecyl Dimethyl Ammonium Chloride, Didecyldimonium Chloride, DDAC, 7173-51-5

Didecyl Dimethyl Ammonium Chloride (DDAC)

Didecyl Dimethyl Ammonium Chloride, commonly known by its acronym DDAC, is a high-efficacy chemical compound belonging to the class of quaternary ammonium compounds (QACs or "quats") . It is widely recognized for its powerful antimicrobial properties and its function as a cationic surfactant.

Here is a comprehensive breakdown of its identity, properties, applications, and safety considerations.

1. Identity and Nomenclature

DDAC is a synthetic organic biocide. As you noted, it is a tetra-substituted ammonium compound where the nitrogen atom carries a permanent positive charge.

• Chemical Name: Didecyl Dimethyl Ammonium Chloride

• Molecular Formula: C₂₂H₄₈ClN

• Molecular Weight: 362.08 g/mol

• CAS Number: 7173-51-5 (This is the unique numerical identifier for this specific chemical).

Common Synonyms:
It is known by many names in different industries, including:

• DDAC

• Didecyl Dimethyl Ammonium Chloride

• Didecyldimonium Chloride

• Quaternium-12 (The INCI name used in cosmetics and personal care)

• Dioctyl Dimethyl Ammonium Chloride (Less precise, older nomenclature)

• N-Decyl-N,N-dimethyldecan-1-aminium chloride (IUPAC name)

2. Physical and Chemical Properties

• Physical State: While theoretically a colorless crystal at room temperature, it is commercially almost exclusively supplied as a clear to light yellow liquid solution (typically in water or alcohol) for ease of handling. At 20°C, it can appear as a slightly yellowish solid powder.

• Odor: It has a characteristic mild odor, often described as "alcohol-like" or musty.

• Boiling Point: >180°C (Decomposes before boiling).

• Melting Point: Does not have a sharp melting point; it typically melts over a range (approx. 94-100°C).

• Solubility:

  • Soluble in: Water (as a surfactant, it forms micelles), Acetone, and highly soluble in Benzene.

  • Insoluble in: Hexane and other non-polar aliphatic solvents.

• Density: Approximately 0.95 g/cm³ (lighter than water).

• Stability: It is stable under normal conditions but can degrade upon prolonged exposure to air and light (oxidation). Its biodegradability decreases as the length of the alkyl chain increases.

3. Mechanism of Action: How It Works

DDAC's antimicrobial efficacy stems from its chemical structure: a positively charged nitrogen atom with two long hydrophobic (water-repelling) decyl chains and two methyl groups.

1. Electrostatic Attraction: The cell walls of bacteria, fungi, and enveloped viruses are typically negatively charged. The positive charge of the DDAC molecule is strongly attracted to these microbial surfaces.

2. Membrane Disruption: The long decyl chains act like "spears," inserting themselves into the lipid bilayer of the microorganism's cell membrane.

3. Cell Leakage: This insertion disrupts the membrane's integrity, increasing its permeability. Essential intracellular components (like potassium ions, enzymes, and nucleic acids) leak out.

4. Cell Death: The loss of these vital components leads to the immediate death of the microorganism. This makes DDAC a broad-spectrum biocide.

4. Applications and Use Areas

Due to its surface activity and biocidal properties, DDAC is used across various industries:

• Disinfectants and Sanitizers: It is a primary active ingredient in hard surface disinfectants used in hospitals, food processing plants, households, and institutions. It is effective against bacteria, fungi, and viruses.

• Water Treatment: Used as an algaecide and bactericide in industrial cooling towers, swimming pools, and oilfield water injection systems to control microbial slime.

• Wood Preservation: A key component in pressure-treated wood to protect against wood-rotting fungi and insects (termites).

• Agriculture: Used as a microbiostat/fungicide in crop protection and for disinfecting animal housing (barns, poultry houses).

• Personal Care & Cosmetics (Quaternium-12): In low concentrations, it acts as a surfactant and antistatic agent in hair conditioners and fabric softeners.

• Industrial Cleaning: Added to carpet cleaning chemicals and upholstery cleaning products to inhibit bacterial growth caused by organic soils.

5. Production Process (Synthesis)

As you correctly stated, it is produced via a process called quaternization.

• Reactants: A tertiary amine (specifically Didecyl Methyl Amine) reacts with an alkylating agent (specifically Methyl Chloride).

• Reaction: The tertiary amine is converted into a quaternary ammonium salt.
  R₂N-CH₃ + CH₃-Cl → [R₂N(CH₃)₂]⁺ Cl⁻ (where R represents the decyl chain).

• This reaction is carried out in a controlled industrial setting, often in a solvent, to produce the final compound.

6. Human Health and Safety (Toxicology)

DDAC is an effective biocide, which means it is designed to kill living organisms (microbes). Therefore, it requires careful handling. The hazard classifications are serious:

• Acute Toxicity:

  • Oral: Harmful if swallowed. Can cause nausea, vomiting, and headaches.

  • Dermal: Harmful in contact with skin. Causes severe skin burns and irritation (e.g., rash, burning sensation, numbness, itching).

  • Ocular: Causes serious eye damage. Risk of permanent vision loss.

  • Inhalation: Harmful if inhaled. Can cause sore throat and respiratory irritation.

• Environmental Toxicity:

  • Very toxic to aquatic life with long-lasting effects. It is lethal to fish, algae, and other aquatic organisms even at low concentrations. Care must be taken to prevent it from entering waterways.

• First Aid Measures:

  • Skin Contact: Remove contaminated clothing immediately. Wash skin with plenty of water and soap for at least 15 minutes.

  • Eye Contact: Rinse immediately with plenty of water for at least 15 minutes, lifting eyelids occasionally. Seek immediate medical attention.

  • Ingestion: Do NOT induce vomiting. Rinse mouth and seek medical help immediately.

  • Inhalation: Move to fresh air.

In summary, Didecyl Dimethyl Ammonium Chloride (DDAC) is a powerful and versatile chemical essential for public health (disinfection), material preservation (wood), and industrial processes (water treatment). However, its potency requires that it be handled with respect, using appropriate personal protective equipment (PPE) to avoid direct contact.