1. Product Overview
2,3-Dimethylbenzothiazolium Iodide (CAS 169939-93-9) is a quaternary ammonium salt featuring a benzothiazole core with two methyl substituents (at the 2- and 3-positions) and a counter-ion of iodide. With the molecular formula C₉H₁₀INS and a molecular weight of 291.16 g/mol, this compound is a versatile reagent in diazocoupling reactions, photochemical processes, and the synthesis of cyanine dyes. The quaternary nitrogen and the iodide anion make it a useful precursor for generating reactive intermediates and for applications in materials science, particularly in the development of photosensitizers and optical materials.
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2. Key Features and Benefits
• Quaternary Ammonium Salt: The permanently charged nitrogen atom provides strong electrostatic interactions and makes the compound water-soluble, facilitating its use in aqueous-phase reactions.
• Reactive C2-Methyl Group: The methyl group at the 2-position is activated by the adjacent quaternary nitrogen, making it susceptible to condensation reactions with aldehydes (Knoevenagel condensation) to form styryl dyes and other conjugated systems.
• Iodide Counter-Ion: The large, polarizable iodide anion can participate in halogen bonding and is a good leaving group for nucleophilic substitution reactions at the C2 position.
• Benzothiazole Core: The fused aromatic-benzothiazole system provides a rigid, planar structure with good photophysical properties (fluorescence, solvatochromism).
• High Purity: Supplied at ≥95% or ≥98% (HPLC), with minimal levels of starting materials or dealkylated byproducts.
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3. Major Applications
• Diazocoupling & Dye Synthesis: The C2-methyl group can be condensed with aromatic aldehydes to form styryl dyes and unsymmetrical cyanine dyes, which are used as photosensitizers, in photodynamic therapy, and as fluorescent probes.
• Photochemical & Optical Materials: The benzothiazole chromophore, combined with the quaternary nitrogen, makes this compound a precursor to materials with interesting photophysical properties, such as nonlinear optical (NLO) materials and fluorescent sensors.
• Nucleophilic Substitution: The C2-methyl group can be deprotonated and used as a nucleophile in alkylation reactions, or the iodide can be displaced by other nucleophiles at the C2 position.
• Organic Synthesis: Used as a building block for more complex quaternary ammonium compounds, including phase-transfer catalysts and antimicrobial agents.
• Materials Science: Incorporated into polymer backbones or as a side-chain modification to introduce ionic conductivity or photoreactivity.
• Academic Research: Investigated in methodology development for quaternary ammonium salt chemistry, nucleophilic aromatic substitution, and the synthesis of functional dyes.
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4. Technical Specifications
Item Description
Product Name 2,3-Dimethylbenzothiazolium Iodide
Synonyms 2,3-Dimethylbenzo[d]thiazol-3-ium Iodide; 3-Methyl-2-methylbenzothiazolium Iodide
CAS Number 169939-93-9
Molecular Formula C₉H₁₀INS
Molecular Weight 291.16 g/mol
MDL Number —
PubChem CID 71395433
Assay (Purity) ≥95% / ≥98% (HPLC)
Appearance White to light yellow crystalline powder
Melting Point ~180–250 °C (decomposes, typical for quaternary ammonium iodides)
Boiling Point Not applicable (decomposes before boiling)
Density ~1.65 g/cm³ (Predicted)
pKa (Predicted) ~-5.0 to -7.0 (Quaternary N, permanently charged)
Calculated LogP ~1.0–1.5 (log D at pH 7 would be much lower due to ionization)
Polar Surface Area (PSA) ~32.1 Ų
Hydrogen Bond Donors 0
Hydrogen Bond Acceptors 1 (S)
Rotatable Bonds 0 (rigid bicyclic)
Solubility Soluble: Water (moderate to high, as quaternary ammonium salt), Methanol, Ethanol, DMSO, DMF, Acetone, Acetonitrile.
Slightly Soluble:DCM, Chloroform, THF.
Insoluble:Hexane, Ether.
Spectral Data (Predicted) ¹H NMR (DMSO‑d₆, 400 MHz): δ 2.55 (s, 3H, C2-CH₃), 3.85 (s, 3H, N3-CH₃), 7.40–8.10 (m, 4H, benzothiazole H), 8.50 (br s, 1H, aromatic H).
¹³C NMR (DMSO‑d₆):δ 14.0 (C2-CH₃), 33.0 (N3-CH₃), 110–155 (benzothiazole Cs), 165.0 (C2, quaternary).
SMILES C[N+]1=C(C)SC2=CC=CC=C21.[I-]
InChI Key —
Storage (Powder) 2–8 °C or RT, sealed, protected from light & moisture; stable ≥12–18 months
Sensitivity Light-sensitive (iodide can oxidize to I₂); store protected from light
HS Code 2934.99.90 / 3822.90.00 (Research Chemical)
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5. Storage and Handling
• Storage: Store in a tightly sealed container at 2–8 °C (or room temperature for short-term), protected from light (amber vial or aluminum foil wrap). The iodide anion is susceptible to aerial oxidation to I₂ (which colors the compound yellow to brown); store in a desiccator for maximum shelf life. Stable for ≥12–18 months under proper conditions.
• Handling: Allow vial to reach room temperature before opening to prevent moisture condensation. Dissolve in water, MeOH, EtOH, DMSO, or DMF as required. Minimize light exposure during handling.
• Solution Preparation: Highly soluble in water and polar organic solvents. Prepare fresh for critical reactions; DMSO/ethanolic stocks are stable at -20 °C for 1–3 months.
• Quaternary Ammonium Reactivity: The C2-methyl group is activated for condensation (Knoevenagel) with aldehydes under basic conditions. The iodide can be exchanged for other anions (PF₆⁻, BF₄⁻, Cl⁻) via metathesis in aqueous or alcoholic solution.
• Light Sensitivity: Discoloration (yellowing) indicates I₂ formation; the compound can be purified by recrystallization from MeOH/EtOH or by passing through a short column of activated charcoal.
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6. Safety Summary (Full SDS Highlights)
• GHS Classification: GHS07 – Warning
• Signal Word: Warning
• Hazard Statements:
• H302: Harmful if swallowed.
• H315: Causes skin irritation.
• H319: Causes serious eye irritation.
• H335: May cause respiratory irritation.
• H373: May cause damage to organs (liver/kidney) through prolonged or repeated exposure (organic iodine compound).
• Precautionary Statements:
• P261: Avoid breathing dust/mist/vapors. Use only in a well-ventilated area or fume hood.
• P264: Wash hands, forearms, and face thoroughly after handling.
• P270: Do not eat, drink, or smoke in areas where this material is used.
• P271: Use only outdoors or in a well-ventilated area.
• P280: Wear protective gloves (nitrile), safety glasses with side shields, and lab coat.
• P301+P312: IF SWALLOWED: Call a POISON CENTER or physician if you feel unwell.
• P302+P352: IF ON SKIN: Wash with plenty of soap and water.
• P304+P340: IF INHALED: Remove person to fresh air and keep comfortable for breathing.
• P305+P351+P338: IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses if present and easy to do. Continue rinsing.
• P330: Rinse mouth if swallowed.
• P337+P313: If eye irritation persists: Get medical advice/attention.
• P403+P233: Store in a well-ventilated place. Keep container tightly closed.
• P501: Dispose of contents/container in accordance with local, regional, and national regulations.
• First Aid Measures:
• Inhalation: Remove to fresh air. If breathing difficult, administer oxygen and seek medical attention.
• Skin Contact: Immediately wash with plenty of soap and water. Remove contaminated clothing. Seek medical advice if irritation or rash develops.
• Eye Contact: Flush immediately with copious lukewarm water for at least 15 minutes. Remove contact lenses if possible. Seek medical attention.
• Ingestion: Rinse mouth. Do NOT induce vomiting. Give water to drink if conscious. Seek medical advice.
• Fire-Fighting Measures:
• Suitable Extinguishing Media: Water spray, alcohol-resistant foam, dry chemical, or CO₂.
• Special Hazards: Combustion may produce highly toxic fumes including HI (hydrogen iodide), I₂ (iodine vapor), SOₓ, CO, and NOₓ. Hydrogen iodide and iodine are extremely toxic and corrosive.
• Protective Equipment: Wear self-contained breathing apparatus (SCBA) and full protective clothing.
• Spill Response:
• Avoid dust generation. Sweep up and place in a suitable closed container for disposal. Do NOT use combustible materials for cleanup. Prevent runoff from entering waterways or drains. Ventilate area after cleanup.
• Handling & Storage:
• Handle in fume hood. Keep container closed when not in use. Store at 2–8 °C, protected from light and moisture. Keep away from strong oxidizers (e.g., peroxides, hypochlorites) and strong bases.
• Hazardous Decomposition Products: Hydrogen iodide (HI), iodine (I₂), sulfur oxides (SOₓ), nitrogen oxides (NOₓ), carbon monoxide (CO), carbon dioxide (CO₂).
• Intended Use: For laboratory research and development ONLY. Not for human or veterinary therapeutic, diagnostic, or food use. Handle as a potentially hazardous organic iodine compound.
