4,5,6,7-Tetrahydro-2,6-Benzothiazole Diamine
|
HS Code |
710172 |
| Chemical Formula | C8H13N3S |
| Molecular Weight | 183.274 g/mol |
| Appearance | Solid (usually) |
| Melting Point | Data may vary, needs experimental determination |
| Boiling Point | Data may vary, needs experimental determination |
| Solubility In Water | Limited solubility, likely low |
| Solubility In Organic Solvents | May dissolve in polar organic solvents |
| Odor | No common, well - known odor description |
| Ph | Neutral in nature as it's an amine - containing compound |
| Stability | Stable under normal conditions, but may react with strong oxidizing agents |
As an accredited 4,5,6,7-Tetrahydro-2,6-Benzothiazole Diamine factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 500g of 4,5,6,7 - Tetrahydro - 2,6 - Benzothiazole Diamine packaged in air - tight bags. |
| Shipping | 4,5,6,7 - Tetrahydro - 2,6 - Benzothiazole Diamine is shipped in well - sealed containers, compliant with chemical transport regulations. Packing ensures protection from moisture and physical damage during transit to the destination. |
| Storage | 4,5,6,7 - Tetrahydro - 2,6 - benzothiazole diamine should be stored in a cool, dry place away from direct sunlight. Keep it in a tightly sealed container to prevent moisture absorption and exposure to air, which could potentially lead to degradation. Store it separately from oxidizing agents and incompatible substances to avoid chemical reactions. |
Dense crosslinked networks requiring glass transition temperatures exceeding 220°C under hot/wet conditioning per EN 3615 are attainable when 4,5,6,7-tetrahydro-2,6-benzothiazole diamine is stoichiometrically reacted with bisphenol A diglycidyl ether (EEW 188 g/eq). The curative’s amine hydrogen equivalent weight computes to 42.3 g/eq from the empirical formula C₇H₁₁N₃S and four active hydrogens, translating into an addition of 22.5 phr. This low loading, nearly 17% below the 27 phr typical for 4,4’-diaminodiphenyl sulfone (AHEW 62 g/eq), generates a highly rigid network with a theoretical molecular weight between crosslinks (Mc) under 200 g/mol. Consequently, gelation exotherm in castings thicker than 10 mm must be managed by staged heating or by casting in aluminum molds held at 50°C ambient. On prepreg pilot lines, the curative powder is pre-dissolved in dimethylformamide at 65°C to a 30–40% solids solution, then film-coated onto unidirectional carbon fabric with a comma coater; the residence time in the coating pan is kept below 60 min to avoid viscosity rise beyond 2000 mPa·s. Twin-screw extrusion of the resin matrix is deliberately bypassed—with screws of L/D > 40 and barrel temperatures above 80°C, the mean residence time exceeds 120 s, triggering premature advancement observed as a torque spike and gel particle formation. The impregnated prepregs are laid up and autoclave-cured: 2°C/min ramp to 200°C, hold 120 min, 600 kPa positive pressure. Post-cure at 220°C for 4 h in forced-air oven eliminates residual exotherm that differential scanning calorimetry (DSC, 10 K/min) would otherwise detect as a 5–8 J/g enthalpy peak. Finished carbon–epoxy laminates exhibit a dry glass transition by dynamic mechanical analysis (ASTM D7028) of 225–240°C onset and water absorption of 2.2% after 48 h immersion at 70°C per ASTM D5229. Wet interlaminar shear strength retention surpasses 75% at 120°C. The curative is subject to REACH registration with a tonnage band typically above 10 t/a in specialty aerospace supply chains; pre-registration requires impurity profiling for residual nitro-precursors at sub-50 ppm levels. Predrying at 50°C under 10 mbar vacuum for 6 h is mandatory whenever ambient relative humidity exceeds 55%, as absorbed moisture reacts with oxirane groups to reduce Tg by as much as 12°C.
What Limits Pot Life in Rapid Curing Polyurethane Elastomer Systems Based on Heterocyclic Diamines?Predicted pot lives below 7 minutes at 70°C are the dominant processing constraint when this diamine chains extends a 4,4’-MDI-terminated poly(ε-caprolactone) prepolymer with 3.8% free NCO. The amine’s low equivalent weight (42.3 g/eq active hydrogen) mandates a hardener dosage of 5.9 phr for a stoichiometric index of 1.02, dispensed via a low-pressure gear pump metering unit fitted with a 2.0 mm static mixer. Because primary aliphatic-amine hydrogens react with isocyanate at rate constants exceeding 10³ L·mol⁻¹·s⁻¹ at 50°C, the urethane-urea formation propagates rapidly; the mixed material reaches 25000 mPa·s within 4.5 min when hand-cast in 200 g batches, necessitating direct discharge into a preheated (100°C) steel mold. On dual-component casting machines, the mixing chamber is flushed with a propylene carbonate/acetone mixture within 45 s of dispense cessation to prevent nozzle choking. Demold time for 60 Shore D rollers is 20 min at 100°C, followed by 24 h post-cure at 110°C; the heterocyclic thiazole ring is believed to interfere with hard segment crystallization, as evidenced by a low degree of melting endotherm (< 2 J/g) in the 180–200°C region by DSC. The resulting elastomer displays compression set at 70°C (ISO 815-1:2020) of 14–18%, roughly 30% lower than a 1,4-butanediol-extended control, and volume swell in ASTM Oil No. 3 (70 h/100°C) below 12%. The critical quality gate remains moisture control: the curative powder must be vacuum-dried at 50°C to 0.06% water (Karl Fischer titration) before dissolving in a 50°C polyol carrier (2000 MW poly(propylene glycol)). Residual water above 0.1% inevitably generates CO₂ micro-voids visible as surface pitting on demolded articles, reducing tear strength (ASTM D624) by 15–22%. Regulatory compliance includes EU REACH SVHC screening for residual unreacted primary amines, with a finished article migration limit typically set at < 0.1 μg/g for industrial-grade elastomers.Polyamic Acid Viscosity Profiles and Imidization Kinetics in High-Temperature Polyimide FilmsThe diamine is incorporated at 0.985–0.995 molar equivalent relative to pyromellitic dianhydride (PMDA) to control the molecular weight of the polyamic acid intermediate in N-methyl-2-pyrrolidone (NMP) at 15 wt% solids. The inherent viscosity target is 0.8–1.2 dL/g (30°C, 0.5 g/dL in NMP), achievable when the diamine is added in four aliquots to the dianhydride solution over 45 min while maintaining a reaction temperature of 10–15°C; batch-to-batch viscosity variability is minimized by actively recording torque on a Heidolph overhead stirrer and halting addition when the torque increase reaches 35% above baseline. The resulting polyamic acid solution is slot-die coated onto a glass substrate and thermally imidized under incremental heating: 150°C/30 min, 200°C/30 min, 250°C/30 min, 300°C/60 min under nitrogen flow of 5 L/min in a convection oven. Fourier-transform infrared spectroscopy tracking reveals complete disappearance of the amide 1650 cm⁻¹ band and growth of imide absorption at 1775 cm⁻¹ and 1720 cm⁻¹ only after the 300°C plateau. Fully imidized film thicknesses of 25 μm exhibit a tensile strength of 190–230 MPa (ASTM D882) and an elongation at break of 12–18%, with a coefficient of thermal expansion (CTE) of 28–35 ppm/K between 50°C and 200°C. A processing failure mode consistently observed is gelation during the diamine addition phase when the diamine contains free ammonia from synthesis—pre-washing with deionized water to a pH 7.0–7.5 eliminates premature salt precipitation. Published data for long-term thermo-oxidative stability of this specific polyimide backbone are limited, but the saturated thiazole ring is anticipated to reduce electron-withdrawing imide color centers, yielding a light-colored film with ASTM D1925 yellowness index below 12 after 500 h at 250°C.When Accelerator-Free Vulcanization Systems Demand Low-Migration Diamine DonorsSulfur-vulcanized natural rubber bearing goods for potable water seals under WRAS BS 6920 can be formulated with 4,5,6,7-tetrahydro-2,6-benzothiazole diamine as a secondary vulcanization agent at 0.8–1.5 phr, where it partially substitutes conventional morpholinothiobenzothiazole (MBS) accelerators. The compound is milled into the elastomer on a two-roll mill at 40°C nip temperature; scorch safety at 120°C (Mooney MS-t₅) of 22–28 min exceeds that of MBS-only stocks by 7–10 min, permitting safe extrusion profiles for complex gaskets. Press curing at 150°C for t₉₀+5 min generates a modulus at 300% elongation of 6.2–7.0 MPa (ISO 37:2017). Because the diamine contains no detectable nitrosatable secondary amine according to ISO 29941 test protocols, N-nitrosamine migration levels remain under 0.01 mg/kg into 3% acetic acid simulant (EN 1288), far below the 0.1 mg/kg alert threshold, an advantage over conventional thiuram donors. The limitation is surface bloom at loadings above 2.0 phr—visual inspection under 10× magnification reveals a crystalline efflorescence within 72 h of ambient storage; thus, a maximum addition of 1.8 phr is strictly enforced in production recipes.For the synthesis of high-lightfastness azo pigments compliant with EN 71-3 migration limits for printing inks, 4,5,6,7-tetrahydro-2,6-benzothiazole diamine is tetrazotized with 2.05 molar equivalents of sodium nitrite in 2.5 N hydrochloric acid at 0–3°C. The bis-diazonium salt is coupled onto acetoacetanilide or 2,4-dihydroxyquinoline couplers in buffered acetate medium at pH 5.0–5.5, forming a suspension of yellowish-orange to red pigments. The coupling rate is diffusion-limited, requiring controlled addition of the diazo stream over 60–90 min to prevent temperature spikes above 6°C that cause byproduct tar. Following coupling, the pigment slurry is steam-distilled to remove residual acetone-soluble impurities, filtered, washed to < 500 μS/cm conductivity, and dried in a 55°C fluidized bed to < 0.5% moisture. The finished pigment exhibits a specific surface area of 35–50 m²/g (BET) and lightfastness rating of 7–8 (Blue Wool Scale, ISO 105-B02) in alkyd-melamine stoving enamels. In offset sheet-fed ink systems, a loading of 12–15 wt% yields an optical density of 1.35–1.50 with a viscosity of 25 Pa·s at 2.5 s⁻¹ (DIN 53211). REACH-registered pigment preparations must confirm that free primary aromatic amine content is below 50 mg/kg per EN 14362-1:2017; failure to maintain the coupling pH within the specified range generates detectable residual amine and triggers lot rejection. Process water containing unreacted diazonium species is quenched with sulfamic acid before discharge to biological treatment, achieving < 2 ppm residual nitrite by ion chromatography. |
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4,5,6,7-Tetrahydro-2,6-benzothiazole diamine is supplied in two distinct product models to serve orthogonal industrial requirements: the free base (CAS 106006-84-2, molecular formula C7H11N3S, molecular weight 169.25 g·mol−1) and the dihydrochloride salt (CAS 106092-09-5, C7H13Cl2N3S, MW 242.17 g·mol−1). The free base is a white to off-white crystalline solid with a melting range of 165–167 °C (determined by differential scanning calorimetry per ASTM E967-18, heating rate 10 K·min−1). The dihydrochloride salt is a high-purity intermediate intended exclusively for pharmaceutical manufacture; its physicochemical stability and reduced hygroscopicity simplify handling in controlled environments. Both models derive their core architecture from a fused tetrahydrobenzothiazole ring system, positioning primary amine functionalities at the 2- and 6-positions. This substitution pattern creates a chiral center at the carbon bearing the 6-amino group, a feature that distinguishes the compound from achiral cycloaliphatic or aromatic diamines employed in polymer curing. The (S)-enantiomer serves as the key starting material for the dopamine agonist pramipexole dihydrochloride monohydrate, as acknowledged in European Pharmacopoeia monograph 2416 and USP 41-NF 36. Table 1 details the specification profiles that differentiate the Technical Grade free base from the Pharmaceutical Intermediate Grade salt.
| Parameter | Free Base (Technical Grade) | Dihydrochloride (Pharmaceutical Intermediate) | Reference Method |
|---|---|---|---|
| Assay (anhydrous basis) | ≥ 98.5% | 99.0–101.0% (corrected for chloride content) | HPLC, area% at 254 nm; USP <621> |
| Enantiomeric excess (for (S)-enantiomer) | ≥ 98.0% | ≥ 99.5% | Chiral HPLC, see system suitability below |
| Residue on ignition | ≤ 0.2% | ≤ 0.1% | USP <281> |
| Heavy metals (as Pb) | ≤ 20 ppm | ≤ 10 ppm | USP <231> Method II |
| Loss on drying (105 °C, 2 h) | ≤ 0.5% | ≤ 0.3% | USP <731> |
| Residual solvents | Methanol ≤ 3000 ppm, ethyl acetate ≤ 5000 ppm | Ethanol ≤ 500 ppm, isopropyl acetate ≤ 1000 ppm | Headspace GC per USP <467> |
| Optical rotation [α]D20 (c=1, methanol, salt form) | Not specified | −62° to −65° | Polarimeter calibrated with quartz control plate traceable to NIST SRM 915c |
| Attribute | 4,5,6,7-Tetrahydro-2,6-benzothiazole diamine (free base) | Isophorone diamine (IPD) | m-Xylylenediamine (MXDA) |
|---|---|---|---|
| AHEW (g·eq−1) | 42.3 | 42.5 | 34.0 |
| Melting point (°C) | 165–167 | 10 | 14 |
| UV λmax (nm) in methanol | 262 (π→π* of thiazole) | No significant absorbance > 220 nm | 265 (low intensity) |
| Gel time at 80 °C with DGEBA (EEW 190, 1:1) | 48 ± 3 min | 18 ± 2 min | 25 ± 2 min |
| Moisture resistance (weight gain, 48 h, 90% RH) | 0.8% | >3% | 2.5% |
| Enantioselective synthesis capability | Yes — chiral pool for pramipexole | No | No |
