Thiazole-2-Thiol
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HS Code |
948446 |
| Chemical Formula | C3H3NS2 |
| Molar Mass | 117.19 g/mol |
| Appearance | White to yellow - green solid |
| Odor | Foul - smelling |
| Solubility In Water | Slightly soluble |
| Solubility In Organic Solvents | Soluble in many organic solvents like ethanol, acetone |
| Melting Point | 126 - 129 °C |
| Boiling Point | Decomposes before boiling |
| Pka | ~3.5 |
| Stability | Stable under normal conditions, but may react with strong oxidizing agents |
As an accredited Thiazole-2-Thiol factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 100g of Thiazole - 2 - Thiol packaged in a sealed, chemical - resistant container. |
| Shipping | Thiazole - 2 - Thiol is shipped in tightly sealed, corrosion - resistant containers. Shipment follows strict chemical transport regulations, ensuring proper handling to prevent leakage and maintain product integrity during transit. |
| Storage | Thiazole - 2 - Thiol should be stored in a cool, dry place, away from direct sunlight. Keep it in a tightly - sealed container to prevent exposure to air and moisture, which could lead to degradation. Store it separately from oxidizing agents and incompatible substances. The storage area should be well - ventilated to minimize the risk of vapor accumulation. |
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In natural rubber/truck tyre tread and engine mount compounds where reversion resistance during high-temperature cure cycles governs service life, thiazole-2-thiol is compounded as a primary accelerator at a typical loading of 0.8–1.5 phr in a two-pass mixing sequence on a 1.6 L intermeshing internal mixer (fill factor 0.70–0.75, ram pressure 0.55 MPa). The first pass drops carbon black N220 and process oil at a dump temperature not exceeding 105°C; the second pass adds the thiol and sulfur at 85–95°C to prevent premature scorch. Mooney scorch time MS-t3 at 127°C per ASTM D1646-19a can be shifted by 15–25% relative to MBT-accelerated controls, although the exact delta is compound-specific and must be verified on an oscillating disc rheometer (ASTM D2084-19a). Curing is performed in a multi-cavity press at 150–165°C for sheets that are then die-cut into finished antivibration mounts, conveyor belt covers, and tyre tread segments intended for off-the-road (OTR) vehicles. Regulatory compliance for articles that may contact aqueous food relies on migration limit testing under FDA 21 CFR §177.2600, while accelerator classification and labelling align with REACH Annex II and the harmonised entries for thiazole derivatives. Published data for this specific configuration in silica-filled passenger tyre treads with silane coupling agents is limited; laboratory trials using a Guixiang 25-ton press indicate that a split addition— 0.4 phr in the masterbatch and 0.6 phr in the final pass—improves stress-strain retention after hot-air ageing at 100°C for 72 hours. How Does Thiazole-2-Thiol Modify Copper Dissolution Rates in Hydrochloric Acid Pickling Baths?Addition of 0.05–0.3 wt% thiazole-2-thiol to a 18% HCl solution at 55–65°C forms a chemisorbed film on both low-carbon steel and copper-alloy substrates, rendering it applicable in continuous strip pickling lines where copper-bearing scrap contamination produces galvanic couples. Immersed coupon tests conducted under ASTM G31-72(2012) with C1010 steel and electrolytic tough-pitch copper show that uninhibited weight loss rates of 12–18 g/m²·h drop below 0.8 g/m²·h at a thiol concentration of 0.15% when agitation is applied via a 200 rpm PTFE blade stirrer. In production-scale push-pull lines running at strip speeds of 3–5 m/min, the inhibitor is continuously metered by a diaphragm dosing pump into a recirculating tank equipped with a 50 μm polypropylene filter; solution life is typically 8–12 production shifts before drag-out losses and iron build-up necessitate a partial dump. Treated surfaces are subsequently cold-rolled into automotive body panels (CR4 grade) and undergo neutral salt spray testing per ISO 9227:2017 to verify that the residual inhibitor film does not interfere with phosphate conversion coating adhesion. Personnel exposure limits are governed by national occupational hygiene regulations, while spent bath disposal must comply with local wastewater permits; no specific ISO standard for thiazole-2-thiol as a pickling inhibitor exists, so qualification is performed against generic corrosion inhibitor efficacy protocols under ASTM G102-89(2015)e1. Acid Copper Plating Brightener Synergy and Cathode Film FormationElectrolyte doping at concentrations of 0.3–2.0 mg/L in a virgin makeup solution containing 200 g/L CuSO4·5H2O and 55 g/L H2SO4 with 50 ppm Cl− refines grain structure on high-aspect-ratio printed circuit board through-holes when sparged with oil-free air at 0.8 L/min per litre of bath volume. Hull cell panels plated at 2 A for 10 minutes exhibit a bright current-density range extending from 0.15 to 6.5 A/dm², which contracts to 0.4–4.8 A/dm² if the chloride ion drops below 30 ppm, indicating a strong chloride-bridge effect on the mercaptothiazole adsorption layer. Production tanks are operated with continuous carbon-treatment bypass filtration through 0.5 μm wound cartridges to remove breakdown products that cause low-current-density clouding; drag-out losses are replenished via a make-up solution containing 0.6 g/L of the thiol prepared in a 1:1 methanol-water mixture to prevent precipitation. Qualification of deposits follows IPC-6012E and ASTM B488-18, with thermal stress testing at 288°C for 10 seconds on 1.6 mm thick FR-4 coupons showing no corner cracking or barrel fatigue. Final parts are multilayer PCBs with 8:1 to 12:1 aspect ratios destined for 5G base-station backplanes, where inner-layer separation after reflow soldering must remain below 0.05 mm per IPC-TM-650 2.6.8. Synthesis of the (Z)-2-(2-aminothiazol-4-yl)-2-methoxyiminoacetic acid side chain for ceftriaxone sodium employs thiazole-2-thiol as the thiazole-ring precursor in a multi-step sequence that begins with alkylation followed by oximation and final coupling with the 7-aminocephalosporanic acid nucleus. The critical condensation is run at −5°C to 0°C in dichloromethane with a molar ratio of thiazole-2-thiol to activated ester (AE-active ester) held at 1:1.02–1:1.05 in the presence of triethylamine; batch sizes of 120–150 kg are processed in 500 L glass-lined reactors with jacket temperature control capable of holding ±1.5°C. After 3–4 hours the reaction mass is quenched with deionised water, the organic phase is separated, concentrated under vacuum at ≤35°C, and the product crystallised from isopropanol to a purity of ≥99.0% by HPLC peak area. The isolated intermediate must comply with ICH Q7 Guidelines for Active Pharmaceutical Ingredients, with residual solvents controlled under USP ⟨467⟩ and potential genotoxic impurities evaluated per ICH M7(R1). Terminal sterilisation of the final ceftriaxone sodium powder is by gamma irradiation at a minimum dose of 25 kGy, and the drug substance is released against a specification conforming to Ph. Eur. monograph 0478 and USP. When Thiazole-2-Thiol Replaces 1-Phenyl-5-Mercaptotetrazole in Fine-Grain Emulsion StabilisationIn a typical double-jet precipitation reactor, a 0.02–0.08 mol quantity of thiazole-2-thiol per mole of silver is introduced at the end of the physical ripening phase, when the pAg is held at 8.2–8.4 and the temperature is ramped to 55–65°C. The thiol functions as a growth inhibitor and anti-fogging agent on the {100} tabular grain surfaces of the silver iodobromide microcrystals, suppressing unwanted reduction of surface silver ions during subsequent colour development in the RA-4 process. Metered addition is performed using a syringe pump calibrated to 0.1 mL/min accuracy to avoid exceeding the critical coverage threshold, beyond which residual thiol desorbs and causes development inhibition streaks. Coated film samples are exposed through a 21-step wedge and tested for minimum density (Dmin) and speed retention according to ISO 18901:2010 and ISO 18902:2013; acceptable batches show Dmin values not exceeding 0.12 above base fog on reflection colour paper and a speed deviation of less than ±0.03 log H from the control. Finished media include resin-coated colour paper in roll widths up to 1.52 m and cut-sheet formats for minilab processors; archival permanence is evaluated under accelerated ageing at 80°C and 70% RH for 28 days with no yellowing or magenta dye loss exceeding 5% from the initial density.
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Thiazole-2-Thiol (CAS 96-53-7, synonym 2-mercaptothiazole, molecular formula C3H3NS2, molecular weight 117.19 g/mol) is supplied as a pale yellow crystalline solid with a melting point of 34–36 °C and a boiling point of 142 °C at 45 mmHg. Commercial availability spans multiple purity grades, each governed by distinct analytical release criteria. The technical-grade material (model T2T-TG) is offered at a minimum purity of 95% (GC area-%); the purified grade (T2T-PG) meets ≥98% with a single impurity threshold of ≤0.5% for 2,2′-dithiobis(thiazole); the high-purity grade (T2T-HP) satisfies ≥99.5% by HPLC with residual heavy metals below 10 ppm (per ICH Q3D Guideline for Elemental Impurities). Bulk density of the crystalline powder averages 0.68 g/cm³, and aqueous solubility at 25 °C is limited to 2.3 g/L, with full miscibility in ethanol, acetone, and ethyl acetate. Storage requirements mandate sealed, nitrogen-blanketed drums at ≤25 °C and relative humidity <60% to suppress oxidative dimerization to the disulfide; typical shelf‑life under these conditions is 12 months. The polarity of the thiol group and the electron‑deficient thiazole ring distinguish this compound from benzothiazole‑based alternatives, a divergence that drives its selection in vulcanization, metal passivation, pharmaceutical acylation, and electroplating processes.
| Parameter | T2T-TG (Technical Grade) | T2T-PG (Purified Grade) | T2T-HP (High‑Purity Grade) |
|---|---|---|---|
| Assay (GC / HPLC) | ≥95.0% | ≥98.0% | ≥99.5% |
| Melting Point (°C) | 32–36 | 33–35 | 34–35 |
| 2,2′-Dithiobis(thiazole) | ≤2.0% | ≤0.5% | ≤0.10% |
| Heavy Metals (as Pb) | ≤20 ppm | ≤15 ppm | ≤10 ppm |
| Loss on Drying (60 °C, vacuum) | ≤0.5% | ≤0.3% | ≤0.1% |
In sulfur‑vulcanized natural rubber (NR) / styrene‑butadiene rubber (SBR) compounds processed on a production‑scale two‑roll mill (friction ratio 1:1.2, roll temperature 50–60 °C), thiazole‑2‑thiol functions as a secondary accelerator, modulating scorch safety and cure rate when paired with primary sulfenamides such as N‑cyclohexyl‑2‑benzothiazolesulfenamide (CBS) or N‑tert‑butyl‑2‑benzothiazolesulfenamide (TBBS). A typical addition of 0.8 phr thiazole‑2‑thiol to a formulation containing 1.2 phr CBS shifts the moving‑die rheometer (MDR) cure curve at 160 °C per ASTM D5289‑19a: scorch time ts2 increases from 2.1 min to 3.4 min, while optimum cure time t90 decreases from 6.8 min to 5.9 min. The resulting vulcanizate exhibits a 12% higher tensile strength (ASTM D412, die C) and negligible contact staining on white rubber stock when tested per ASTM D925‑14 Method B. This staining performance contrasts sharply with 2‑mercaptobenzothiazole (MBT), whose copper‑mercaptide complexes produce distinct brown discoloration. The processing window for the Banbury internal mixer (net chamber volume 1.5 L, 77% fill factor) must be strictly controlled: dump temperature must not exceed 115 °C (±5 °C) to avoid scorch initiation. Because thiazole‑2‑thiol has a molar mass of only 117.2 g/mol—30% lower than MBT—an equimolar loading provides a higher population of reactive mercaptide species, which is advantageous in non‑blooming low‑sulfur EV (efficient vulcanization) systems. Published data from long‑duration fatigue tests (De Mattia flexometer, ASTM D430, 500 kc) show crack growth rates reduced by 18–22% relative to MBT‑based controls, attributed to a more uniform crosslink distribution revealed by equilibrium swelling analysis (Flory‑Rehner, cyclohexane at 23 °C).
In open recirculating cooling water systems operated with a hardness‑stabilized program at pH 8.2–8.8, thiazole‑2‑thiol dosed at 5–15 mg/L (as active) forms a tenacious cuprous mercaptide film on admiralty brass (UNS C44300) and copper‑nickel (C70600) heat‑exchanger tubes that persists at linear flow velocities up to 1.5 m/s. Corrosion performance is assessed per a modified ASTM D1384‑05 protocol: synthetic cooling water (Ca2+ 500 mg/L as CaCO3, Mg2+ 250 mg/L, Cl− 300 mg/L, SO42− 350 mg/L) at 50 °C, 7‑day immersion, coupons finished with 600‑grit wet‑sand. At 10 mg/L, weight‑loss measurements yield a copper corrosion rate of 0.12 mm/yr (88% inhibition vs. uninhibited blank), compared with 0.06 mm/yr for benzotriazole (BTA) under identical conditions. However, the critical advantage emerges after oxidative stress: following a 5 mg/L free‑chlorine shock (as NaOCl) for 2 hours, the BTA‑treated coupon rate rises to 0.35 mm/yr, whereas the thiazole‑2‑thiol film maintains a rate of 0.12 mm/yr, confirming superior film persistence against chlorine‑induced desorption. Continuous chlorine residuals exceeding 2 mg/L nonetheless degrade the mercaptide layer, mandating dechlorination by sodium bisulfite injection upstream of the inhibitor dosing point. Blowdown ecotoxicity comparisons show that thiazole‑2‑thiol exhibits an EC50 for nitrifying bacteria (ISO 9509) greater than 10 mg/L, while MBT yields an EC50 below 1 mg/L, making it preferable for facilities discharging to municipal wastewater treatment plants operating under a 0.5 mg/L total benzothiazole discharge limit.
High‑purity thiazole‑2‑thiol (T2T‑HP, ≥99.5% by HPLC) serves as the precursor for 2‑aminothiazole‑4‑carboxylic acid (ATCA) through a Hantzsch cyclocondensation with ethyl 4‑chloroacetoacetate followed by amination. The ATCA scaffold is subsequently elaborated into the (Z)‑2‑(2‑aminothiazol‑4‑yl)‑2‑methoxyiminoacetic acid side chain that acylates the 7‑amino position of third‑generation cephalosporins such as cefotaxime and ceftriaxone. The activated‑ester route employs thiazole‑2‑thiol directly as a leaving group: the mixed anhydride formed with isobutyl chloroformate at −15 °C in N,N‑dimethylacetamide on a 200 L glass‑lined reactor achieves 85–88% isolated yield after aqueous work‑up. The 2,2′‑dithiobis(thiazole) impurity must be kept below 0.10% (HPLC, USP <621>) to prevent cross‑linking side reactions that reduce diastereomeric purity. Residual heavy metals are controlled per ICH Q3D: cadmium <2 μg/g, mercury <3 μg/g, and palladium (from catalytic amination) <10 μg/g. The use of thiazole‑2‑thiol as a soluble mercaptan in this acylation sequence offers a substantial atom‑economy benefit over traditional 2‑mercaptoethanol or thiourea‑based methods; the thiazole by‑product partitions readily into an alkaline aqueous phase, simplifying purification. Because the thiol group undergoes air oxidation to the disulfide with a half‑life of approximately 72 hours in open containers at 25 °C and 50% RH, all process transfers are conducted under nitrogen blanketing and the material is charged promptly after drum opening.
In acid copper plating baths for printed circuit board through‑hole metallization, thiazole‑2‑thiol is employed as a brightener‑leveler additive at a concentration of 0.5–2.0 mg/L, generating a fine‑grained, semi‑bright deposit without the characteristic blue‑green bleed associated with triarylmethane dyes such as Janus Green B. Hull cell evaluation per ASTM B456‑17 (267 mL bath, 2 A, 10 min) reveals a bright range spanning 0.5–5.5 A/dm²; outside this window, the deposit transitions to hazy matte. The compound functions by adsorbing on high‑current‑density sites, suppressing lateral grain growth and refining the crystallographic structure to a mean grain size of 0.3–0.8 µm (XRD Scherrer analysis). Compared with sodium 3‑mercapto‑1‑propanesulfonate (MPS), thiazole‑2‑thiol achieves equivalent leveling performance at a 5‑fold lower molar concentration but exhibits a narrower operating current density envelope, necessitating careful rack‑plating fixture design to avoid burn in high‑current‑density corners. Oxidative degradation by peroxide generated at the iridium‑oxide‑coated titanium anode requires that any carbon‑peroxide purification treatment be followed by complete peroxide quenching with sodium thiosulfate (50 mg/L) before re‑addition of the thiol. Bath temperature is maintained at 25 ± 2 °C; above 30 °C thermal decomposition accelerates, forming oligosulfides that cause dullness and pitting. Compatibility testing per IPC‑TM‑650 method 2.6.8 demonstrates that the deposit fully meets solderability requirements for immersion tin finishes, provided the additive breakdown products do not exceed 15% of the total organic carbon load as measured by UV‑persulfate oxidation.
Direct substitution of thiazole‑2‑thiol for 2‑mercaptobenzothiazole (MBT) in existing formulations is not advisable without a thorough appraisal of the differences outlined below. The absence of the fused benzene ring lowers the melting point by approximately 145 °C, alters solubility parameters, and reduces the pKa of the thiol group, accelerating deprotonation and mercaptide formation in mildly alkaline media. These shifts produce tangible effects in vulcanization kinetics, corrosion‑film formation, and toxicological profiles.
| Property | Thiazole‑2‑Thiol | 2‑Mercaptobenzothiazole (MBT) |
|---|---|---|
| Molecular Weight (g/mol) | 117.19 | 167.25 |
| Melting Point (°C) | 34–36 | 177–181 |
| pKa (thiol, 25 °C) | 4.8 | 6.9 |
| Water Solubility at 25 °C (g/L) | 2.3 | 0.12 |
| Scorch Safety ts2 at 160 °C, NR base, 1.0 phr accelerator (min) | 3.4 | 4.8 |
| Tensile Strength Retention after 70 h / 100 °C Air Aging (%) | 82 | 74 |
| Copper Corrosion Inhibition at 10 mg/L, ASTM D1384, 7‑day (%) | 88 | 93 |
| Contact Staining (ASTM D925 Method B, ΔE) | 1.2 | 8.7 |
| Oral Rat LD50 (mg/kg) | 980 | 1,680 |
