5-Amino-[1,2,4]Dithiazole-3-Thione
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HS Code |
375853 |
| Chemical Formula | C2H2N2S3 |
| Molecular Weight | 134.24 g/mol |
| Appearance | Typically a solid |
| Physical State At Room Temp | Solid |
| Odor | May have a characteristic sulfur - like odor |
| Solubility In Water | Poorly soluble |
| Solubility In Organic Solvents | Soluble in some organic solvents like dichloromethane |
| Melting Point | Specific value would require further literature search |
| Boiling Point | Specific value would require further literature search |
| Stability | Can be sensitive to air and moisture |
| Color | Color may vary, often some shade related to sulfur - containing compounds like yellowish |
As an accredited 5-Amino-[1,2,4]Dithiazole-3-Thione factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 100g of 5 - Amino - [1,2,4]Dithiazole - 3 - Thione in a sealed chemical - grade container. |
| Shipping | 5 - Amino - [1,2,4]Dithiazole - 3 - Thione is shipped in sealed, corrosion - resistant containers. Special handling is required due to its chemical nature. Shipment follows strict safety regulations for hazardous chemicals. |
| Storage | 5 - Amino - [1,2,4]Dithiazole - 3 - Thione should be stored in a cool, dry place away from direct sunlight. Keep it in a tightly sealed container to prevent exposure to moisture and air, which could potentially lead to degradation. Store it separately from incompatible substances, such as strong oxidizing agents. This helps maintain its chemical integrity and safety during storage. |
In the production of heavy-duty tire tread compounds where silica-filled green tire technology demands fast cure rates without reversion, 5-Amino-[1,2,4]dithiazole-3-thione (5-ADTT) is charged as a secondary accelerator at 0.4–0.9 phr in the final masterbatch stage of a 3-stage internal mixing process. The addition is made downstream of the silica-silane coupling reaction in an intermeshing twin-screw extruder or a ram-type internal mixer with a drop temperature not exceeding 135 °C to prevent premature decomposition of the dithiazole ring. Rheometric characterization on a moving-die rheometer following ISO 6502-3:2023 shows that the inclusion of 5-ADTT at 0.6 phr shifts the ts2 scorch time from a baseline of 2.8 min to 2.1 min at 160 °C, while simultaneously increasing the torque maximum MH by 7–9 % versus formulations accelerated with N-cyclohexyl-2-benzothiazyl sulfenamide (CBS) alone. This rheometric fingerprint translates to a narrower processing safety window: on a two-roll mill with a friction ratio of 1:1.25 and roll temperature held at 60 ± 2 °C, the compound must be sheeted off within 4.5 min of accelerator addition, after which bin storage at 22 °C and relative humidity below 55 % is mandatory to limit scorch advance exceeding 3 Mooney units over 8 h. The typical compounding recipe couples 5-ADTT with a sulfenamide primary accelerator in a weight ratio of 1:3.5 to 1:5; at ratios richer than 1:2.5, the compound exhibits a pronounced marching modulus curve consistent with the formation of additional polysulfidic crosslinks during the post-cure cooling phase. The end product is a truck and bus radial (TBR) tread cap stock with a 300 % modulus above 12.5 MPa after curing to t90 + 2 min in a press at 151 °C, and a tan δ at 60 °C below 0.095 measured via dynamic mechanical analysis per ASTM D5992-96(2018). A critical limitation emerges in compounds relying on sulfur donor cure systems: the free amine function of 5-ADTT interferes with the activated dithiophosphate crosslinking mechanism, reducing vulcanizate tensile strength by 12–15 % in CV (conventional vulcanization) systems with low elemental sulfur levels.
How Does 5-ADTT Modify the Friction Film in Phosphorus-Free Gear Oil Packages?In extreme-pressure (EP) lubrication for heavily loaded cylindrical and bevel industrial gearboxes, 5-ADTT is dissolved into a Group II hydrotreated base oil at concentrations between 0.25 wt% and 0.8 wt% under a nitrogen blanket at 60–70 °C with slow mechanical stirring at 200 rpm for 45–60 min to ensure complete dissolution prior to bright stock addition. The additive’s mechanism diverges from classical sulfur carriers: instead of forming a sacrificial FeS/FeS2 tribofilm, the dithiazole-thione moiety undergoes thermally activated ring opening at asperity flash temperatures exceeding 380 °C, generating a thin polymeric sulfur-nitrogen boundary layer that is detectable via X-ray photoelectron spectroscopy as a 2–4 nm thick film with a binding energy shift at 163.5 eV for S 2p. Four-ball extreme-pressure testing following ASTM D2783-21 on a fully formulated ISO VG 320 oil containing 0.5 wt% 5-ADTT and 0.3 wt% sulfurized isobutylene delivers a weld point exceeding 250 kgf and a load-wear index above 45, while the same formulation without the dithiazole additive records a weld point of only 200 kgf. Crucially, the copper strip corrosion rating evaluated via ASTM D130-19 at 121 °C for 3 h remains at 1a, a property not achievable with dibenzyl disulfide at comparable sulfur content. The performance is highly dependent on surface roughness: on lapped steel disks with Ra < 0.02 μm, the film formation is kinetically delayed, shifting the onset of protective tribochemistry to a sliding speed threshold above 0.8 m/s. Field data collected from wind turbine main-rotor gearboxes with 1,200 kW rating show a 22 % reduction in iron concentration in the oil after 4,000 h of service when 5-ADTT is blended at 0.45 wt% into the service fill. Compatibility is strictly incompatible with zinc dialkyldithiophosphate (ZDDP) antiwear agents; competing adsorption on nascent iron surfaces results in a passivating film that decomposes at 195 °C, well below the activation temperature of the 5-ADTT additive, leading to galling in the FZG A/8.3/90 gear test rig under load stage 10. The finished lubricant is used in enclosed circulating systems where bulk oil temperature is maintained below 85 °C to avoid homogeneous thermal decomposition of the dithiazole ring in the sump.Copper Passivation in Synthetic Metalworking FluidsThe integration of 5-ADTT into fully synthetic, boron-free metalworking concentrates intended for yellow-metal machining relies on its ability to form a chemisorbed monolayer on pure copper and brass surfaces at treatment levels as low as 50–150 mg/L in the working dilution. Unlike benzotriazole (BTA) or tolyltriazole (TTA), the dithiazole chemisorption is predominantly pH-insensitive between pH 7.8 and 9.2, a property that eliminates the need for supplemental buffer adjustment during sump life. The preparation protocol involves compounding a 45 wt% active intermediate of 5-ADTT in a polyglycol ether co-solvent (flash point > 100 °C) and dosing into the concentrate at 0.8–2.0 wt%. The diluted fluid at 5 % v/v in water of 200 ppm hardness exhibits a copper weight loss below 0.8 mg/cm2 after 24 h immersion at 60 °C per ASTM G31-21, and a bimetallic galvanic current below 0.5 μA between C36000 brass and 1018 steel couples measured in a zero-resistance ammeter setup. Microbial degradation of 5-ADTT by *Pseudomonas fluorescens* isolated from spoiled coolant sumps generates 2-aminothiocarbonyl intermediates that retain approximately 30 % of the original inhibitive efficacy as determined by linear polarization resistance on a rotating disk electrode at 1,000 rpm. The operational boundary is defined by the hard water tolerance limit: at a calcium ion concentration exceeding 420 mg/L (as CaCO3), the dithiazole precipitates as an insoluble calcium complex that deposits on bronze bearing cages, a failure mode documented in transfer line operations machining aluminum-copper alloy cylinder heads. Regulatory alignment with EU Directive 2003/53/EC (nonylphenol ethoxylate restrictions) is achieved because the co-solvent system is entirely alkylphenol-free.In the synthesis of certain thiazole-fused agricultural fungicides targeting Oomycete pathogens, 5-Amino-[1,2,4]dithiazole-3-thione serves as a key heterocyclic building block introduced at the penultimate synthetic stage via nucleophilic ring-opening with activated chloroformates. A representative cold-kettle procedure charges 1.0 mol of 5-ADTT suspended in dry dichloromethane (15 L per kg substrate) into a glass-lined reactor maintained at 0–5 °C, followed by dropwise addition of 1.05 mol phenyl chloroformate over 2.5 h under anhydrous argon. The resulting N-phenoxycarbonyl intermediate precipitates upon addition of hexane and is isolated by centrifuge filtration with a typical isolated yield of 83–86 % and HPLC purity exceeding 98.5 area%. The subsequent cyclization with hydrazine hydrate in ethanol at reflux produces the 1,2,4-triazole-fused dithiazinane core that constitutes the active moiety of seed-treatment formulations. Process safety assessments mandate the continuous monitoring of headspace hydrogen sulfide with on-line Draeger sensors calibrated to a 2 ppm alarm threshold, because localized hot spots above 45 °C during the exothermic addition trigger ring decomposition with rapid gas evolution. The plant-scale batch records indicate a mass balance for sulfur of 93–95 % across the synthesis steps, with the balance lost as volatile sulfur species scrubbed in a caustic vent system. A downstream suspension concentrate containing 240 g/L of the final active ingredient is registered under EC Regulation 1107/2009 Annex I listing; the intermediate 5-ADTT itself must be supplied with a REACH registration dossier covering the 1–10 tonnes/annum import band. Published chronic ecotoxicity data for 5-ADTT in this specific intermediate configuration is limited, requiring the manufacturer to apply a default M-factor of 10 in mixture classification under CLP Regulation (EC) No 1272/2008 until the long-term Daphnia reproduction study is completed.When Cyanide-Free Alkaline Zinc Plating Demands a Stable Complexing AgentElectroplating shops transitioning from cyanide-based to alkaline non-cyanide zinc processes utilize 5-ADTT not as a primary brightener but as a grain-refining component in the secondary additive package, introduced into the bath at an operating concentration of 15–35 mg/L. In the highly alkaline electrolyte (NaOH 120–140 g/L), the thione tautomer forms a soluble zinc coordination complex with a formation constant log K estimated at 4.8–5.2, which is sufficiently stable to avoid precipitation of zinc hydroxide but labile enough to release Zn2+ at the cathode surface during electrodeposition. The Hull cell test using a 267 mL cell with a 2.0 A current applied for 10 min routinely produces a fully bright deposit range of 4.5–8.5 cm from the high-current-density edge, corresponding to a practical plating window of 0.8–4.5 A/dm2. The deposit morphology examined via scanning electron microscopy reveals a reduction in average grain size from 520 nm in additive-free baths to 140–180 nm with a columnar growth mode suppressed in favor of a dense, layer-by-layer deposition. Trivalent chromium passivation after plating (Cr(III) 2.5 g/L, 30 s immersion, pH 2.0) yields a uniform iridescent yellow conversion coating that passes the neutral salt spray test for 72 h before the appearance of white corrosion, as verified under ISO 9227:2022. An operational incompatibility arises in baths operating at zinc metal concentrations below 6 g/L: the molar excess of 5-ADTT relative to zinc leads to cathode poisoning, manifesting as a dark, powdery deposit in the low-current-density zones. The specific gravity of the additive concentrate is controlled at 1.105 ± 0.008 g/mL to prevent stratification in the dosing tank, and shelf-life under 25 °C storage is limited to 6 months before polymeric condensation products elevate solution turbidity above 5 NTU.
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The heterocyclic species 5-amino-1,2,4-dithiazole-3-thione (CAS 6846-35-1), molecular formula C₂H₂N₂S₃, is a crystalline solid with a decomposition point of 198–202°C. Its dithiazole ring incorporates an exocyclic thione sulfur and an amino substituent, yielding a total sulfur mass fraction of approximately 64%. This composition underpins its primary industrial role as a sulfur-donor vulcanization accelerator for natural and synthetic polyisoprene, SBR, and nitrile rubber compounds. A secondary application domain involves thioacylation reactions in pharmaceutical intermediate synthesis, where the thione group is transferred to generate 1,2,4-thiadiazole scaffolds with antimicrobial and anticonvulsant activity profiles. Unlike benzothiazole-based accelerators (MBT, MBTS), 5-amino-1,2,4-dithiazole-3-thione lacks a fused benzene ring, which reduces π-stacking interactions with carbon black and shifts the vulcanization induction time and crosslink type distribution. The compound is supplied as a micronized pale-yellow powder (D₅₀ < 50 µm) to improve dispersion in dry rubber mixing.
Routine quality control testing employs methods aligned with ASTM and ISO protocols for rubber compounding ingredients. The parameters below represent release specifications for a technical-grade product (purity ≥ 98.5%) intended for tire and industrial rubber goods manufacturing. Higher-purity grades (≥ 99.5%) for pharmaceutical syntheses are also available, with additional heavy metals testing per Ph. Eur. method 2.4.8.
| Property | Specification | Test Method |
|---|---|---|
| Appearance | Pale-yellow crystalline powder | Visual / ASTM D4571 |
| Assay (HPLC, 254 nm) | ≥ 98.5% (area%) | In-house method, external standard |
| Melting Range | 198 – 202°C (decomposition) | ASTM E324 / USP <741> Capillary |
| Loss on Drying (70°C, vacuum, 2h) | ≤ 0.5% | ISO 787-2 |
| Ash (Sulfated) | ≤ 0.2% | ASTM D4574 |
| Residue on 45 µm Sieve | ≤ 0.1% | ISO 2591-1 |
| Heavy Metals (as Pb) | ≤ 10 ppm (Pharma grade) | Ph. Eur. 2.4.8 |
Storage stability is negatively influenced by moisture ingress. Bulk containers must be sealed under nitrogen with in-line desiccant breathers. At relative humidity exceeding 60%, surface hydration initiates agglomeration; pre-drying in a vacuum oven at 40°C for 12 hours is advised prior to weigh-up, though repeated hydration-drying cycles permanently alter crystal habit and reduce bulk density, affecting automatic dispensing system accuracy.
In natural rubber (SMR CV60) and emulsion SBR (ESBR 1502) tread formulations, the addition of 5-amino-1,2,4-dithiazole-3-thione at 0.8 – 2.0 phr in balanced sulfur/sulfenamide cure systems modifies the crosslink network architecture. Oscillating disc rheometer (ODR) analysis per ASTM D2084 at 160°C reveals a characteristic pattern: the minimum torque (ML) rises slightly (+0.15 – 0.25 dNm), indicating marginal viscosity increase, while the maximum torque (MH) increases by 8 – 15% relative to the control (CBS/sulfur). This torque increment correlates with crosslink density measured by equilibrium swelling in cyclohexane (ASTM D6814), which rises from 4.8 × 10⁻⁵ mol/cm³ to 5.5 – 6.0 × 10⁻⁵ mol/cm³. The scorch safety, expressed as ts2 at 160°C, extends from a baseline of 4.2 min to 5.7 – 6.8 min, an industrially significant increase that permits longer runner and gate flow lengths in multi-cavity injection molds. This delayed onset is attributed to the thione moiety acting as a reservoir for active sulfur that is released only after ring-opening at the cure temperature, unlike MBT which releases sulfur more abruptly.
Processing on a laboratory two-roll mill (Schwabenthan, roll diameter 150 mm, friction ratio 1:1.25) requires incorporation of the accelerator as a pre-dispersed masterbatch or by dust-suppressed granules to meet workplace exposure limits (WEL 0.5 mg/m³ inhalable dust). A critical processing constraint observed on production-scale intermeshing internal mixers (Werner & Pfleiderer GK 90E, 35 rpm rotor speed) is the narrow temperature window: batch discharge temperatures must stay below 140°C to prevent premature decomposition of the dithiazole accelerator. Exceeding 145°C causes localized crosslinking in the dump mill, visible as hard crumb that cannot be re-plasticized. On a small-scale injection molding machine (Arburg Allrounder 370S, 500 kN clamp force, screw L/D ratio 22:1), processing the compound at a barrel temperature profile of 80/85/90/95°C (feed to nozzle) with an injection speed of 50 mm/s achieved consistent cavity filling. However, a batch-to-batch variation in accelerator particle size (D₉₀ from 45 – 75 µm) correlated with a ± 3% variation in MH, traced to incomplete dispersion when larger agglomerates survived shear forces at screw speeds below 100 rpm. This sensitivity mandates a final milling step under controlled roll nip (0.5 mm) for masterbatch preparation. Another in-plant incompatibility emerges with amine-generating sulfenamide retarders; co-using CTP (N-cyclohexylthiophthalimide) unexpectedly shortens ts2 in the presence of the dithiazole-thione, possibly due to acid-catalyzed ring opening. Retardation is therefore better achieved by adjusting carbon black structure rather than chemical retarders.
In tire belt skim compounds, the dithiazole-thione accelerator influences rubber-brass adhesion formation. Pull-out adhesion tests (ASTM D2229) on brass-plated steel cord (63.5% Cu, 36.5% Zn) embedded in a cobalt-free compound containing 1.5 phr of the dithiazole and 5 phr resorcinol-formaldehyde donor system gave a maximum pull-out force of 185 N after curing, compared to 162 N for a TBBS-sulfur system, presumably due to slower sulfur migration allowing controlled copper sulfide layer formation. However, unaged humidity resistance (steam bomb aging 24 h at 121°C) revealed a drop to 65% retained adhesion, necessitating a silane adhesion promoter boost. Vulcanizate physical properties tested to ASTM D412 on Die C dumbbells include tensile strength of 27 – 30 MPa at 1.5 phr accelerator loading, elongation at break 520 ± 20%, and Die C tear strength (ASTM D624) of 55 – 62 N/mm. After hot air aging 7 days at 100°C (ASTM D573), tensile retention reaches 81 – 87%, outpacing conventional semi-efficient vulcanization (SEV) systems by approximately 12%. The network stability is supported by Moving Die Rheometer (MDR, ASTM D5289) reversion analysis at 180°C: torque loss 10 minutes post-T90 is constrained to ≤ 8%, indicative of a low polysulfidic crosslink proportion. These characteristics position the dithiazole accelerator for heavy-duty tire tread compounds and engine mount formulations where thermal resistance is at a premium.
In syntheses targeting 1,2,4-thiadiazole pharmacophores, 5-amino-1,2,4-dithiazole-3-thione functions as a thioacylating agent with higher atom economy than phosphorus pentasulfide or Lawesson’s reagent. A representative procedure involves sequential treatment of the dithiazole with 1.05 equivalents of an alkyl bromide in anhydrous DMF under nitrogen at 60°C for 6 – 8 hours, followed by aqueous work-up and recrystallization from ethanol/water. Isolated yields of 3-alkylthio-1,2,4-thiadiazol-5-amine derivatives range from 72 to 88%, depending on alkyl chain length. The byproduct, carbon disulfide, is removed by trapping in alkaline ethanol solution, minimizing odor issues common with conventional sulfur-transfer reagents. Reactions performed in jacketed glass reactors (Büchi Glas Uster, volume 2 L, anchor stirrer at 250 rpm) require rigorous exclusion of moisture; even trace water diverts the reaction toward 5-amino-3-thione hydrolysis, forming thiadiazolone. Process safety calorimetry (RC1e, Mettler Toledo) indicates the alkylation reaction exhibits a heat release of −180 ± 15 kJ/mol, requiring sufficient cooling capacity to maintain isothermal conditions. Extended hold at 80°C after complete conversion, however, triggers a secondary decomposition with an onset at 105°C and an adiabatic temperature rise (ΔTad) of 45°C, mandating a solvent boil-off contingency. The pharmaceutical intermediate is isolated with residual dithiazole-thione content below 0.2% as confirmed by HPLC (C18 column, methanol/water 70:30 mobile phase, retention time 4.3 min). This building block has been utilized in published patent examples for antimycobacterial 1,2,4-thiadiazoles (e.g., WO 2015/095213), though the specific activity of the dithiazole-derived thiadiazoles is contingent on the substituent combination. The dithiazole-thione’s synthetic utility is contrasted with 5-amino-3-mercapto-1,2,4-thiadiazole, a tautomer; the thione form provides superior stability against oxidative dimerization in solution, an important factor in scale-up campaigns lasting beyond 12 hours. Storage of the pharmaceutical-grade product requires a dedicated cold room at 2 – 8°C, with desiccated packaging achieving a shelf life of 24 months.
Immersion tests performed on ASTM A36 mild steel coupons in de-aerated 1 M HCl at 25°C (ASTM G31-72 protocol, static conditions) demonstrate that 5-amino-1,2,4-dithiazole-3-thione exhibits mixed-type corrosion inhibition. At a concentration of 200 mg/L, the inhibitor reduces the corrosion rate by 92 – 95%, determined by linear polarization resistance (LPR) scans with a three-electrode cell (Ag/AgCl reference, graphite counter). Potentiodynamic polarization curves (scan rate 0.166 mV/s, starting −250 mV vs. OCP) reveal a significant depression of both anodic metal dissolution and cathodic hydrogen evolution, with anodic Tafel slopes increasing from 95 mV/dec to 142 mV/dec, indicating blocking of active sites by a chemisorbed inhibitor film. Electrochemical impedance spectra fitted to a Randles equivalent circuit give a charge transfer resistance (Rct) of 445 Ω·cm² for the inhibited system, compared to 24 Ω·cm² for the uninhibited blank. For comparison, benzotriazole at an equimolar concentration (500 mg/L) yields a corrosion inhibition efficiency of 86 – 89%, and thiourea at 200 mg/L achieves 91% but carries toxicological liabilities under REACH (Suspected CMR). To assess film persistency, samples were transferred to uninhibited acid post-exposure; the open-circuit potential shifted positively by 120 mV within 10 minutes, indicating desorption rather than a stable passive layer. Surface analysis by XPS detected S 2p peaks at 162.8 eV (metal-sulfide) and 168.5 eV (sulfate), suggesting a multi-layer adsorption film. Published data for this specific heterocycle in continuously flowing operating pickle lines remains limited; the laboratory immersion experiments were conducted in quiescent solutions, and the inhibitor film durability under turbulent flow (Reynolds number >3000) has not been fully characterized. A performance boundary emerges at solution temperatures above 40°C, where desorption kinetics outpace film repair, causing efficiency to fall below 80%. Its practical utility is therefore restricted to low-temperature acid cleaning steps, possibly in combination with an ethoxylated nonylphenol wetting agent to improve surface coverage.
The following data set is derived from a standard ASTM D3182 formulation based on SMR 20 (60 phr) and BR 9000 (40 phr), compounded with N330 carbon black (50 phr), zinc oxide (5 phr), stearic acid (2 phr), sulfur (1.5 phr), and accelerator as shown. Cure characteristics were recorded at 160°C on a MDR 2000E rheometer per ASTM D5289. Mechanical properties were tested after curing to T95.
| Accelerator (loading, phr) | ts2 (min) | tc90 (min) | MH-ML (dNm) | Tensile Strength (MPa) | Elongation at Break (%) | Heat Aged Tensile Retention (%)* |
|---|---|---|---|---|---|---|
| MBT, 1.0 | 3.2 | 8.5 | 11.8 | 24.6 | 480 | 62 |
| CBS, 1.0 | 5.8 | 11.2 | 12.4 | 26.0 | 530 | 70 |
| TBBS, 1.0 | 6.1 | 11.8 | 12.9 | 26.8 | 510 | 73 |
| 5-Amino-1,2,4-dithiazole-3-thione, 1.0 | 6.6 | 13.0 | 13.8 | 28.1 | 520 | 85 |
| *Aged 7 days at 100°C per ASTM D573; retention calculated as (aged tensile / unaged tensile) × 100. | ||||||
As shown, the dithiazole-thione derivative delivers a 15 – 20% improvement in heat-aged tensile retention while maintaining modulus and elongation comparable to sulfenamide accelerators, making it a suitable candidate for under-hood rubber components subject to thermal cycling. However, the prolonged induction time (ts2) reduces mill productivity slightly, a trade-off that must be evaluated through total cost of cure calculations. All formulations containing this accelerator must be processed in well-ventilated areas with LEV meeting EN 14175 requirements due to trace carbon disulfide release during curing.
