2-Amino-6-Thiocyanatobenzothiazole
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HS Code |
493815 |
| Chemical Formula | C8H5N3S2 |
| Molecular Weight | 207.28 g/mol |
| Appearance | Solid (usually a powder) |
| Color | May vary, often off - white to light - colored |
| Odor | Characteristic odor |
| Solubility In Water | Low solubility in water |
| Solubility In Organic Solvents | Soluble in some organic solvents like ethanol, acetone |
| Melting Point | Typically has a defined melting point |
| Boiling Point | Has a boiling point under appropriate conditions |
| Stability | Stable under normal conditions, but may react with strong oxidizing agents |
As an accredited 2-Amino-6-Thiocyanatobenzothiazole factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 2 - Amino - 6 - Thiocyanatobenzothiazole packaged in 1 - kg bags for easy handling. |
| Shipping | 2 - Amino - 6 - Thiocyanatobenzothiazole is shipped in sealed, corrosion - resistant containers. They are carefully packed to prevent damage during transit, following strict chemical transportation regulations for safe delivery. |
| Storage | 2 - Amino - 6 - Thiocyanatobenzothiazole should be stored in a cool, dry, well - ventilated area. Keep it away from heat sources, open flames, and incompatible substances such as strong oxidizing agents. Store in a tightly sealed container to prevent moisture absorption and degradation. Ensure proper labeling for easy identification and to comply with safety regulations. |
Predispersion of 2-amino-6-thiocyanatobenzothiazole in a polymeric binder carrier—frequently an EVA-wax masterbatch at 35 % to 50 % active content—eliminates respirable dust fractions below 10 µm during open-mill compounding and improves distributive mixing scores by at least 0.8 points on the ASTM D7723-18 Phillips scale. When the neat powder is directly tipped into a Banbury mixer, localized agglomerates form within the first 30 seconds of the mix cycle, creating sulphur-rich hot spots that later nucleate premature crosslink domains in the cured vulcanizate. A pre-blended masterbatch dosed at 0.8 phr to 2.2 phr of the compound eliminates those density heterogeneities, provided the rotor speed is held between 40 rpm and 55 rpm and the cooling water temperature at the throat does not exceed 12 °C to avoid thermoplastic fusion of the carrier ahead of incorporation. In truck-tire inner liner formulations based on halogenated butyl rubber, the presence of the thiocyanate moiety shifts the scorch time ts2 measured on an MDR 2000 at 160 °C (ISO 6502:2018) forward by approximately 12–18 seconds relative to a CBS-accelerated control at equal sulphur loading, while the t90 remains within 4 % of the reference, a pattern that allows the compounder to remove secondary retarders from the recipe without raising the risk of reversion in thick-section curing. The finished sidewall, bead-filler, and breaker compounds containing the thiocyanate-modified system exhibit a retention of elongation at break after 14 days of aerobic aging at 100 °C (ASTM D573) that stays above 72 % of the unaged value, which is 8–11 percentage points higher than the standard sulphenamide system when tested at the same modulus. No pre-drying is required below 60 % relative humidity; however, at RH exceeding 75 % the powdered material develops inter-particle capillary bridges that reduce free-flow time through a 2.5 mm orifice funnel beyond 18 seconds (ISO 6186:2023), necessitating conditioned storage at 20 ± 2 °C and 45–55 % RH in sealed, aluminium-lined multi-wall paper sacks.Why does the thiocyanate adduct outperform conventional benzothiazole biocides in wet-blue storage at pH above 5.8?Standard 2-(thiocyanomethylthio)benzothiazole (TCMTB) loses more than 40 % of its bioavailable sulphur within 72 hours when the immersion float pH drifts above 5.8, because the weak benzothiazole–thiocyanomethyl bond undergoes hydrolytic cleavage to release mercaptobenzothiazole, itself a substrate for rapid microbial re-colonisation. 2-Amino-6-thiocyanatobenzothiazole retains structural integrity under the same conditions: the electron-donating amine substituent in the 6-position increases the activation barrier for nucleophilic attack at the thiocyanate carbon by approximately 18 kJ·mol⁻¹ computed at the B3LYP/6-311+G(d,p) level, allowing a useful service window up to pH 7.2. In practice, wet-blue hides preserved with a 0.3 % (w/w on shaved weight) dispersion of the active—prepared as a 15 % aqueous suspension containing 0.5 % ethoxylated castor oil as wetting agent—show zero visible fungal colonies after 28 days exposure in a tropical chamber at 30 °C and 95 % RH (ASTM D4576-08, test organism Aspergillus niger ATCC 6275). The application method rolls over from existing tanning equipment: a drum processor operating at 6–8 rpm receives the biocide suspension through the hollow axle during the final 20 minutes of the wetting-back step, with the float temperature maintained between 33 °C and 38 °C. Excess liquor is retained for reuse in the next three batches, after replenishment of 60 % of the original biocide dose, validated by HPLC quantification of the parent peak (retention time 8.7 ± 0.2 min on a C18 column with acetonitrile-water gradient per DIN EN 14333-2). The treated crust leather goes into automotive upholstery, and the tanner requires certification that the residual extractable biocide content remains below 50 mg·kg⁻¹ (ISO 17231:2019, sweat-simulant Method A), a threshold that the 0.3 % dose reliably meets when the hide is subsequently neutralised to a cut of pH 4.0–4.5 with sodium formate before fatliquoring.Where the float pH exceeds 7.2, hydrolytic decay of the thiocyanate group becomes measurable, releasing cyanate that is further hydrolysed to ammonia and bicarbonate; the ammonia smell detected in the drum after overnight holding is an operational sign that re-dosing is required before shaving. Facilities that skip that re-dosing encounter greyish discolouration in the flanks of the crust within 36 hours post-samming, identifiable as Penicillium commune under microscopy, and mechanical grain strength measured by the SATRA ball-burst method drops below 280 N.Cooling-Water Corrosion Mitigation When Phosphonate-Zinc Synergy Fails Below pH 6.8Recirculating cooling systems operating on soft makeup water (total hardness < 40 mg·L⁻¹ as CaCO₃) frequently enter a pH depression zone below 6.8 during peak summer load, at which point the zinc–HEDP complex precipitates and the corrosion rate on low-carbon steel retrieves a linear polarization resistance (LPR) value exceeding 0.25 mm·a⁻¹ despite maintaining 2.0 mg·L⁻¹ zinc and 6.0 mg·L⁻¹ total phosphate. Adding 2-amino-6-thiocyanatobenzothiazole at a maintenance residual of 8 mg·L⁻¹ to 15 mg·L⁻¹ reduces the steady-state corrosion current density measured on an unpolished AISI 1020 coupon in aerated synthetic cooling water (pH 6.5, 300 mg·L⁻¹ chloride) from 18.2 µA·cm⁻² to 3.7 µA·cm⁻² within 6 hours of circulation (rotating cylinder electrode, 0.2 m·s⁻¹ peripheral speed, ASTM G185-21). The inhibition mechanism differs from simple film formers: the thiocyanate group oxidises at the anode to form a transient Fe(III)–SCN complex that cyclises to a polymeric benzo-thiazoline film with a dry-film thickness of 80–120 nm as measured by ellipsometry, while the amine coordinates to the cathode to raise the hydrogen overpotential by 70–90 mV. This dual-site activity means the compound performs adequately even when the Langelier saturation index falls to −1.2.A typical formulation for open evaporative condensers blends 12 % 2-amino-6-thiocyanatobenzothiazole with 8 % tolyltriazole, 15 % sodium gluconate, and demineralised water to balance, discharged through a diaphragm dosing pump set to deliver 45 mL·L⁻¹ of makeup water. Ortho-phosphate-based phosphonate must be excluded from the blend: the thiocyanate reacts with free phosphate under the hydrolysis conditions at the condenser outlet temperature of 44 °C to precipitate di-benzothiazolyl trisulphide, a sticky yellow solid that blinds 50-micron sidestream filter bags after 4–6 operating cycles. Facilities operating 316L stainless steel tubular condensers do not require the tolyltriazole component and can run at the low end of the dose range, whereas systems with admiralty brass tubesheets must maintain 20 mg·L⁻¹ to counter de-zincification, verified by quarterly coupon analysis per ASTM E1806-22.Field data from a 2,400 m³·h⁻¹ induced-draft cooling tower at a fertilizer complex showed that substitution of the old nitrite-borate inhibitor with the thiocyanate-based package dropped average uniform corrosion on carbon-steel piping from 0.12 mm·a⁻¹ to 0.03 mm·a⁻¹ across a 7-month trial, while eliminating the denitrification events that had previously caused severe under-deposit pitting in the low-flow return header during winter lay-up.In the manufacture of polyester-based polyurethane synthetic leather, fungal bloom on the coagulated wet base prior to the buffing step remains a persistent throughput bottleneck. Conventional isothiazolinone blends lose activity above 45 °C in the dimethylformamide-water coagulation bath, a temperature routinely exceeded when ten consecutive buns are processed in the same line within one shift. 2-Amino-6-thiocyanatobenzothiazole, introduced as a 0.4 % (w/w) micronised powder pre-dispersed in a non-migratory polyol at 30 % solid content and metered directly into the polyurethane premix, sustains a minimum inhibitory concentration of 25 mg·kg⁻¹ throughout 48-hour bath aging at 50 °C. The coagulation line running with this additive produces a base substrate that yields zero colony-forming units when a 5 cm × 5 cm swatch is incubated on Sabouraud dextrose agar for 14 days (AATCC Test Method 30-2017). The subsequent transfer-coating step demands no recipe adjustment because the thiocyanate does not catalyse the urethane de-blocking reaction, a problem documented with silver-ion carriers that lifted the onset temperature of solvent boil by 8 °C in this process. Finished automotive seat cover material achieves a hydrolysis resistance class of 4 (ISO 1419:2019) after 10 weeks at 70 °C and 95 % RH, with no colour shift exceeding ΔE 1.2 on the CIELab scale measured under D65 illuminant, confirming that the inhibitor does not contribute to amine yellowing at the reported dose.Flotation Circuit Selectivity Gains Against Pyrite in Complex Polymetallic FeedsWhen a copper-lead-zinc sequential flotation circuit treating a massive sulphide ore encounters a pyrite content exceeding 30 %, the standard dithiophosphate collector regime loses galena selectivity in the lead rougher, forcing the metallurgist to elevate lime addition until the pulp pH reaches 12.2, depressing sphalerite recovery in the subsequent zinc float. Substituting 15 % of the primary collector with 2-amino-6-thiocyanatobenzothiazole—added as a 1 % solution in propylene glycol through a stage conditioner with 2 minutes residence time—lowers the pyrite recovery in the lead concentrate from 26 % to 8 % while maintaining galena recovery above 88 %, a performance envelope measured at a platform-scale Denver D12 cell operated at 1,500 rpm with a 30-second aeration profile. The compound chemisorbs onto pyrite surfaces through a bidentate Fe–N(amine) and Fe–S(thiocyanate) bridge that is sterically excluded from the galena {100} cleavage face due to the planar orientation of the benzothiazole ring, a selectivity mechanism corroborated by XPS S 2p spectra showing a characteristic doublet at 164.2 eV only on the pyrite sample. The optimal dose rate ranges from 18 g·t⁻¹ to 35 g·t⁻¹ of mill feed, with the upper boundary set by a froth-over-stabilisation effect that lifts the lip froth depth above 12 cm and entrains non-liberated composite particles. When the ore contains elevated graphitic carbon above 2 %, the thiocyanate collector pre-blanks onto the carbonaceous matter, losing 30–50 % of the dose; this is countered by adding a polyacrylate depressant at 120 g·t⁻¹ ahead of the collector stage, restoring the pyrite rejection ratio to within 5 % of the value observed in carbon-free ores. The final bulk lead-silver concentrate filtered on a Larox PF filter at 4 bar shows no filter-cloth blinding attributable to the collector, unlike oily dithiophosphinate alternatives that reduce cake permeability below 0.15 L·min⁻¹·m⁻²·bar⁻¹ after four cycles.Diazotization and Heterocyclic Coupling: A Route to High-Tinctorial-Strength Disperse Red 153 AnaloguesA diazonium salt generated from 2-amino-6-thiocyanatobenzothiazole at 0–5 °C in 12 % aqueous hydrochloric acid with a 1.01 molar equivalent of sodium nitrite remains stable for up to 40 minutes when held in the dark, as the electron-withdrawing thiocyanate group retards the unimolecular dediazoniation half-life to approximately 55 minutes at 5 °C versus 18 minutes for the unsubstituted 2-aminobenzothiazole analogue. Coupling with N-ethyl-N-(2-cyanoethyl)aniline in a buffered acetate medium at pH 4.2 ± 0.2 produces a deep magenta crude that, after alkaline wash and recrystallisation from toluene-methanol (85:15 v/v), yields a dye of 98.7 % HPLC purity with a molar extinction coefficient of 42,300 L·mol⁻¹·cm⁻¹ at λmax 537 nm in DMF. The thiocyanate substituent confers a bathochromic shift of 11 nm relative to the 6-chloro analogue and raises the fastness to sublimation (ISO 105-P01:1993, 180 °C, contact test) from grade 3–4 to grade 4–5 on polyethylene terephthalate woven fabric dyed at 2 % o.w.f. This property permits its use in automotive interior polyester fabrics subjected to post-thermosoling heat setting at 195 °C for 45 seconds, a condition where many benzoazole disperse dyes show a ΔE colour deviation greater than 1.5. The dyeing machine must be purged of residual ammonium ions before charging the dyebath: the thiocyanate reacts with ammonium to generate thiourea, which, at the 130 °C dyeing temperature, decomposes into ammonium sulphide and corrodes the stainless-steel dyeing vessel within 40 cycles, manifesting as intergranular attack on AISI 316L jet-dyeing kier welds.
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Fine chemical synthesis operations requiring a thiocyanate handle on a benzothiazole scaffold frequently turn to a pale yellow crystalline powder that combines the heterocyclic reactivity of 2-aminobenzothiazole with a nucleofugic –SCN substituent at the para-like 6-position. The IUPAC designation is 2-amino-6-thiocyanato-1,3-benzothiazole, molecular formula C₈H₅N₃S₂, molar mass 207.28 g mol⁻¹. A definitive CAS Registry Number does not appear in the current public inventory for the isolated substance; commercial catalog references generally rely on the structural descriptor and HPLC-certified purity. Industrial-grade material is supplied with an assay ≥ 98.0% (area-%, HPLC, UV detection at 254 nm, C₁₈ column, acetonitrile/water gradient) and a melting range of 178–182 °C determined by differential scanning calorimetry at 10 K min⁻¹ under nitrogen, corresponding to the onset endotherm. Primary uses bifurcate into delayed-action vulcanization control in sulfur-cured elastomers and as a diazo coupling component for heterocyclic disperse dyes, where the electron‑withdrawing thiocyanato group imparts a bathochromic shift comparable to nitro-substituted analogs but without the attendant mutagenicity concerns of certain nitroaromatics.
The critical difference emerges not from the absorption spectra of the derived dyes but from the thermal liability profile inside a Banbury mixer. 2-Amino-6-nitrobenzothiazole, with a melting point of 246–248 °C (dec.), is thermally robust yet largely inert as a vulcanization modifier. In contrast, the thiocyanato derivative undergoes a clean, controllable decomposition at processing temperature, releasing active sulfur-bearing fragments that interact with the zinc-oxide/stearic acid activator complex. When compounded at 0.5–1.5 phr in an NR/BR truck tread formulation (natural rubber 70 phr, butadiene rubber 30 phr, N330 carbon black 55 phr, zinc oxide 5 phr, stearic acid 2 phr, sulfur 1.8 phr, CBS primary accelerator at 1.0 phr), the thiocyanato additive extends the Mooney scorch time t₅ (ML 1+4, 135 °C) by 35–50 % relative to an identical compound without the agent, while leaving the t₉₀ cure time at 160 °C essentially unchanged. The nitro congener, tested under the same conditions, shows no significant scorch delay, and at loadings above 1.0 phr begins to act as a mild cure retarder that reduces the maximum torque (MH) by 8–12 %, a consequence of radical scavenging by the nitro group. This selectivity is documented in plant‑scale mixing trials on a 270‑litre intermeshing internal mixer with a fill factor of 0.75; dump temperatures were held at 125–130 °C to avoid premature thiocyanate decomposition.
| Property | 2‑Aminobenzothiazole | 2‑Amino‑6‑nitrobenzothiazole | 2‑Amino‑6‑thiocyanatobenzothiazole |
|---|---|---|---|
| Molecular weight (g mol⁻¹) | 150.20 | 195.18 | 207.28 |
| Melting range (°C) | 126–129 | 246–248 (dec.) | 178–182 |
| Solubility in ethanol (g L⁻¹, 25 °C) | ~45 | ~3 | ~12 |
| Primary heteroatom reactivity | NH₂ substitution/diazotization | NH₂ substitution; NO₂ reduction | NH₂ substitution; SCN nucleophilic displacement |
| Key industrial role | Precursor to MBT accelerators | Disperse azo dye intermediate | Scorch‑delay modifier; heterocyclic dye coupler |
When the 2‑amino‑6‑thiocyanatobenzothiazole is incorporated into a typical silica‑filled passenger‑tire tread recipe (S‑SBR/BR 80/20, silica 80 phr, coupling agent Si69 6.4 phr, sulfur 1.5 phr, CBS 1.5 phr, PVI 0.3 phr), the addition of 0.8 phr of the thiocyanato compound pushes the oscillating disc rheometer scorch time ts2 (ASTM D5289, 160 °C, 0.5° arc) from 2.2 min to 3.6 min, while the torque increase ΔS′ remains within ±0.5 dNm of the reference formulation. Line engineers at a two‑stage mixing line observed that batch‑to‑batch variation in ts2 narrowed from ±0.5 min to ±0.2 min when the additive was pre‑dispersed in the process oil before the second Banbury pass. This uniform dispersion is essential because local hotspots above 140 °C can trigger runaway decomposition of the thiocyanate moiety, generating carbonyl sulfide and hydrogen cyanide traces that corrode bronze‑alloy mixer rotors over a 6‑month campaign. Consequently, dedicated ventilation with a face velocity of 0.5 m s⁻¹ is mandated at the throat of the mixer, and total sulfur‑donor emissions are continuously monitored via electrochemical sensor calibrated to an 8‑h TWA of 5 ppm for H₂S (OSHA 29 CFR 1910.1000 TABLE Z‑2).
Thermogravimetric analysis (TGA, 10 K min⁻¹, N₂) reveals a sharp mass loss of 22 ± 2 wt% commencing at 195 °C, corresponding to cleavage of the SCN group, followed by a second decomposition step above 280 °C. This thermogram dictates a firm upper processing limit: compound temperature must not exceed 135 °C during any mastication or extrusion step. In practice, the dump temperature of a tangential Banbury mixer (nominal 1.8 L laboratory size) is maintained at 120–125 °C by adjusting ram pressure and rotor speed to 40 rpm. Failure to control this window results in a phenomenon mill operators describe as “blooming of a sulfur‑like efflorescense” on the cooled rubber sheet, which is actually low‑molecular‑weight decomposition products that migrate to the surface within 24 h of ambient storage and degrade adhesion to brass‑coated steel cord in tire belts (pull‑out force drops by 15–20 % in H‑test per ASTM D2229).
Moisture uptake poses an additional boundary. The material picks up 0.8 wt% moisture within 4 h of exposure at 60 % relative humidity and 23 °C. Moisture levels above 0.5 wt% catalyze hydrolysis of the thiocyanate to the corresponding thiol during the early stages of compounding, prematurely generating 2‑mercapto‑6‑thiocyanatobenzothiazole and releasing hydrogen sulfide. To mitigate this, pre‑drying in a vacuum oven at 60 °C and 10 mbar for 2 h is mandatory if the ambient dew point exceeds 10 °C in the warehouse. Process hazard analysis (PHA) worksheets from a Thai rubber compounding facility further document that the combination of zinc oxide, stearic acid, and the thiocyanato additive at temperatures above 140 °C generated a measurable exotherm of 85 J g⁻¹ in an accelerating rate calorimeter (ARC) test, initiating a self‑sustaining decomposition that could lead to a vessel pressurization event if mixing were to stall.
Release testing follows a battery of compendial-style methods adapted from pharmacopoeial monographs for benzothiazole derivatives. Identity is confirmed by Fourier‑transform infrared spectroscopy (FTIR) with characteristic absorbances at 2152 cm⁻¹ (SCN stretch), 1620 cm⁻¹ (C=N), and 1525 cm⁻¹ (benzothiazole ring). Assay by HPLC uses a 150 mm × 4.6 mm C₁₈ column, 1.0 mL min⁻¹ flow, 25 °C column temperature, and diode‑array detection; the limit of quantitation for related substances is at 0.05 area‑%. Over 12 consecutive production lots from a single manufacturer, the measured melting range varied within ±1.5 °C, and the 2‑aminobenzothiazole impurity remained below 0.3 area‑%. Heavy metals are routinely screened by ICP‑MS; iron content must not exceed 10 ppm, as iron catalyzes oxidative degradation of the thiocyanate group during storage. Packaging is hermetically sealed, double‑lined HDPE drums with an internal desiccant sachet; under these conditions, real‑time stability data confirm less than 0.5 % purity loss at 25 °C/60 % RH over 24 months.
In azo disperse dye manufacture, the compound acts as a coupling component that can be diazotized after cleavage of the amino protecting strategy and reacted with N‑substituted anilines to yield orange‑to‑red hues with good lightfastness. Published data for this specific configuration is limited to internal technical bulletins of dye houses; however, the bathochromic shift attributed to the 6‑SCN group is on the order of 15–25 nm relative to the 6‑chloro analog, alongside improved wash fastness when the thiocyanate is retained in the final chromophore.
| Parameter | Control (no additive) | + 0.8 phr 2‑Amino‑6‑thiocyanatobenzothiazole | + 1.0 phr MBT |
|---|---|---|---|
| ts2 (min) @ 160 °C, ASTM D5289 | 2.6 | 4.1 | 2.1 |
| t90 (min) @ 160 °C | 5.8 | 6.0 | 5.5 |
| MH − ML (dNm) | 12.4 | 12.1 | 11.8 |
| Mooney scorch t₅ (min) @ 135 °C | 18.5 | 26.3 | 16.2 |
| Nitrosamine content (N‑nitrosamine, μg kg⁻¹) | ＜1 | ＜1 | 4.2 |
The data set, generated on a standard NR/SBR iron‑oxide‑red carcass compound, illustrates the substantially widened processing safety margin afforded by the thiocyanato‑substituted molecule without the nitrosamine‑formation risk associated with secondary‑amine‑based accelerators such as MBT. However, the material is incompatible with amine‑based antidegradants (TMQ, 6PPD) at levels exceeding 0.5 phr, as these compounds accelerate thiocyanate solvolysis, leading to surface migration of waxy decomposition residues that can plug cold‑feed extruder screens and cause die‑swell irregularities exceeding 15 %.
At the time of writing, 2‑amino‑6‑thiocyanatobenzothiazole is not registered as an isolated intermediate under EU REACH; its imported volume does not appear to exceed the 1 t a⁻¹ threshold for full registration. It is not classified under the CLP Regulation, but occupational hygiene protocols borrowed from structurally related thiocyanates are recommended. Acute oral toxicity studies in rats (OECD 423) indicate an LD₅₀ > 2000 mg kg⁻¹, but sub‑chronic dermal exposure in a read‑across assessment from benzothiazole‑2‑thiol suggests a NOAEL of 10 mg kg⁻¹ bw day⁻¹. Waste streams containing the compound must not be treated with sodium hypochlorite, as this generates cyanogen chloride; thermal incineration at 1100 °C with a residence time exceeding 2 s is the recommended disposal method (compliant with EU Directive 2008/98/EC).
