Comprehensive Introduction to Sodium Allyl Sulfonate

1. Overview

Sodium Allyl Sulfonate (SAS) , also known as Sodium 2-propene-1-sulfonate or Allylsulfonic Acid Sodium Salt, is an organosulfur compound widely utilized in industrial chemistry and polymer science. It functions primarily as a copolymerizable emulsifying agent and a additive for electroplating. The compound is valued for its dual functionality: a reactive vinyl group (C=C) allows for polymerization, while a sulfonate group (-SO₃Na) provides high solubility and ionic characteristics.

2. Chemical Profile

Property	Value
CAS Number	2495-39-8
Molecular Formula	C₃H₅NaO₃S
Molecular Weight	144.13 g/mol
IUPAC Name	Sodium prop-2-ene-1-sulfonate
Appearance	White crystalline powder or granules
Melting Point	242 °C (dec.)
Solubility	Highly soluble in Water (approx. 714 g/L at 20°C); soluble in Methanol and DMF.
Chemical Structure	H₂C=CH-CH₂-SO₃⁻ Na⁺

3. Synthesis and Reactivity

Sodium Allyl Sulfonate is synthesized via the sulfonation of allyl chloride or allyl alcohol, followed by neutralization with a sodium base.

Reactivity:
The molecule contains an electron-withdrawing sulfonate group adjacent to a double bond. This configuration makes the alpha (α) carbon-hydrogen bonds acidic, allowing deprotonation under basic conditions to form a stabilized carbanion. This property allows SAS to participate in nucleophilic substitution reactions, such as those used to create novel polysulfide polymers.

4. Applications

SAS is a critical intermediate in several industrial sectors:

4.1 Polymer Industry (Copolymerization)

SAS is used as a monomer to modify the properties of polymers. When copolymerized with monomers like acrylonitrile, it introduces sulfonate groups into the polymer chain.

• Dyeable Acrylic Fibers: It adds dye-receptive sites to synthetic fibers, improving color uptake.
• Superplasticizers: SAS-based copolymers are used in concrete to improve workability and reduce water content.
• Flocculants & Hydrogels: It enhances water solubility and ionic conductivity, making it effective for water treatment and absorbent materials.

4.2 Electroplating (Metal Finish)

SAS acts as a brightening agent and grain refiner, particularly in nickel and palladium plating baths.

• Mechanism: It adsorbs onto the metal surface during deposition, influencing grain size and morphology. This results in smoother, brighter, and more corrosion-resistant coatings.

4.3 Specialty Chemicals

Recent research highlights SAS as a precursor for high-sulfur-content polymers. Using a water-based synthesis with sodium polysulfides, SAS helps create materials (Poly-S-SAS) that act as powerful desiccants (absorbing up to 345% of their weight in water) or metal remediation agents (removing heavy metals from wastewater).

5. Safety and Handling

While generally stable, proper safety protocols are required when handling SAS powder due to potential irritation.

• Stability: Stable under normal conditions. Incompatible with strong oxidizing agents.
• Storage: Keep container tightly closed in a cool, dry place. Avoid dust formation. It is hygroscopic, so inert gas storage is recommended.
• Toxicity:
  • Acute Oral (Rat): LD50 > 12,300 mg/kg (Low toxicity).
  • Skin/Eye Contact: May cause mechanical irritation or dryness. Prolonged contact may cause dermatitis.
  • Sensitization: May cause allergic skin or respiratory reactions in sensitive individuals.
• Ecotoxicity: Should not be released into the environment without treatment.

6. Regulatory and Identification Information

• EINECS Number: 219-676-5.
• InChI Key: DIKJULDDNQFCJG-UHFFFAOYSA-M.
• Shipping: Generally not classified as hazardous for transport by DOT (Department of Transportation) in dry form, but aqueous solutions may have specific handling requirements.

Comprehensive Introduction Table of Sodium Allyl Sulfonate (SAS)

Item	Detailed Information
Chemical Name	Sodium Allyl Sulfonate (SAS)
Molecular Formula	C3​H5​NaO3​S
Molecular Weight	144.12 g/mol
Structural Feature	Contains one reactive C=C allyl double bond and one anionic sulfonate group −SO3−Na+
Physical Appearance	White crystalline solid; transparent light yellow liquid (aqueous commercial solution)
Water Solubility	Highly soluble in water; insoluble in non-polar organic solvents
Self-Polymerization Tendency	Low homopolymerization activity; weaker self-reaction than acrylic monomers, easy copolymerization
pH Stability	Stable sulfonate anion across pH 2–12; no charge loss under acidic conditions
Key Functional Group Functions	1. C=C double bond: Participates in free-radical copolymerization to graft sulfonate onto polymer backbones 2. −SO3−​: Provides permanent hydrophilicity, electrostatic repulsion, metal ion chelation, salt tolerance
Common Co-Monomers	Acrylamide (AM), DAC, acrylic acid, methacrylic acid, acrylonitrile
Main Application Fields	1. Anionic flocculants for high-salinity wastewater 2. Polycarboxylate superplasticizers for concrete 3. Water-soluble polymer dispersants 4. Antistatic modifiers for fiber & coating resin
Polymerization Methods	Aqueous solution polymerization, water-phase precipitation polymerization (no toxic organic solvent needed)
Thermal Stability	Solid decomposes above 210°C; aqueous solution stable at 60–90°C polymerization temperature
Biodegradability	Moderate biodegradation for monomer; SAS copolymers show better degradation than pure PAM
Toxicity & Eco-Safety	Low acute toxicity; non-carcinogenic; degradation product is harmless sulfate, no eutrophication risk
Storage Requirements	Sealed cool dry storage; avoid strong acid, strong oxidants and long-time high-temperature exposure
Core Advantage vs Carboxylate Monomers	Sulfonate group maintains ionic charge in high-salt/acid water; superior anti-scaling and dispersion performance