2-Methyinaphtho[1,2-D]Thiazole
|
HS Code |
894647 |
| Chemical Formula | C12H9NS |
| Molecular Weight | 199.27 g/mol |
| Appearance | Solid |
| Color | Typically light - colored (varies) |
| Odor | May have a characteristic organic odor |
| Melting Point | Specific value depends on purity (needs experimental determination) |
| Boiling Point | Also purity - dependent and requires experimental data |
| Solubility In Water | Low solubility in water |
| Solubility In Organic Solvents | Soluble in some organic solvents like chloroform, dichloromethane |
| Density | Density value is experimentally determined |
As an accredited 2-Methyinaphtho[1,2-D]Thiazole factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 100g of 2 - Methylnaphtho[1,2 - D]Thiazole packaged in a sealed, chemical - resistant bottle. |
| Shipping | 2 - Methylnaphtho[1,2 - D]Thiazole is shipped in sealed, corrosion - resistant containers. It's transported under conditions avoiding heat, direct sunlight, and incompatible substances to ensure safety during transit. |
| Storage | 2 - Methylnaphtho[1,2 - D]Thiazole should be stored in a cool, dry, well - ventilated area. Keep it away from heat sources, open flames, and oxidizing agents. Store in a tightly closed container to prevent evaporation and contamination. It's advisable to store it in a dedicated chemical storage cabinet, segregated from incompatible substances, to ensure safety. |
In the production of sulfur-cured diene rubber articles, 2-methylnaphtho[1,2-d]thiazole functions as a delayed-action accelerator with a characteristic induction period that permits adequate flow during molding. Incorporation levels between 0.8 and 2.2 phr on a hydrocarbon rubber basis are established by mastication on a two-roll mill with a friction ratio of 1:1.15 at 50–60 °C. Zinc oxide (3–5 phr), stearic acid (1–2 phr), and sulfur (1.5–2.5 phr) form the balance of the cure package. The compounded stock is sheeted out at a thickness of 2.5 mm and conditioned at 23 ± 2 °C and 50 ± 5 % relative humidity for 24 h before rheometric analysis. Cure characteristics are determined on a moving die rheometer (MDR 2000, Alpha Technologies) according to ASTM D5289-19a using a 1° arc and 1.67 Hz oscillation frequency at 160 °C. For a carbon-black-filled natural rubber/butadiene rubber (60/40) blend containing 2.0 phr of the accelerator, the minimum elastic torque (ML) stabilizes at 1.6–2.0 dNm, while the maximum torque (MH) reaches 13.5–15.5 dNm. The scorch time (ts2, time to 2 dNm rise above ML) measures 2.8–3.5 min, and the optimum cure time (tc90) ranges from 8.5–10.2 min. The curing rate index calculated as 100/(tc90 − ts2) yields a value between 16 and 18 min⁻¹. Activation energy for the crosslinking reaction, derived from MDR torque increase data collected at three isothermal temperatures (150 °C, 160 °C, 170 °C) and processed by an Arrhenius fit, is estimated at 85–95 kJ/mol, which positions this heterocyclic accelerator between sulfenamide and thiuram classes in terms of processing latency. On a production-scale intermeshing internal mixer (Banbury 1D, net chamber volume 1.6 L, fill factor 0.75), a typical mixing regime incorporates the accelerator in the second pass at a dump temperature not exceeding 110 °C to preserve scorch safety. The finished vulcanizates exhibit tensile strength of 18–22 MPa (ISO 37:2017, dumbbell type 2) and elongation at break of 450–550 %. Flat-panel compression molding at 160 °C and 15 MPa clamp force produces components such as engine mounts, bridge bearings, and marine fenders that meet the static stiffness and creep requirements of ISO 22768:2020. Moisture content of the accelerator must be maintained below 0.3 wt% (Karl Fischer titration, ISO 760:1978) to prevent microporosity in thick cross‑sections. Storage under nitrogen at temperatures below 30 °C is mandatory to suppress dimerization and the formation of insoluble particulates that cause surface defects in compression‑molded goods. Combinations with dithiocarbamate ultra‑accelerators at equal molar addition produce bloom that exceeds the tolerance limit of 0.5 % surface coverage as determined by photographic image analysis within 72 h of post‑cure storage.At What Loading Does Scorch Safety Become Critical in EPDM Profiles?When EPDM profile extruders raise barrel zone temperatures above 100 °C to maintain a smooth melt surface, the operating margin against premature vulcanization narrows substantially. 2‑Methylnaphtho[1,2‑d]thiazole is evaluated as a replacement for mercaptobenzothiazole (MBT) in a sulfur-donor system containing 1.2 phr sulfur, 5 phr zinc oxide, 1 phr stearic acid, and 60 phr carbon black N550 in an EPDM grade with 4.5 wt% ethylidene norbornene termonomer (Mooney viscosity ML(1+8)125 at 125 °C). Mixing is executed on a tangential internal mixer (fill factor 0.7, rotor speed 40 min⁻¹) with a drop temperature of 130 °C. The compound is cooled rapidly to 40 °C on a sheet-off mill and homogenized in a second pass without curatives. The Mooney scorch behavior measured at 120 °C (ASTM D1646-19a) reveals that a loading of 1.5 phr of the naphthothiazole accelerator delivers a minimum viscosity (70–75 MU) and a time to a five‑point rise (t5) of 14–17 min, which compares favorably against MBT at equimolar addition (t5 typically 9–11 min). The data summarized in the table below originate from a controlled laboratory screening on a standard EPDM formulation and illustrate the trend; the absolute values should be verified on a production compound because the scorch delay in a full-scale extruder is influenced by shear heating and residence‑time distribution.
A Thermally Robust Precursor for Bisbenzoxazolyl Stilbene Optical BrightenersCondensation of 2‑methylnaphtho[1,2‑d]thiazole derivatives with bifunctional aromatic aldehydes yields fluorescent whitening agents (FWAs) of the bisbenzoxazolyl stilbene type, tailored for polyester fiber application. The synthetic strategy first converts the methyl group into a formyl or carboxyl handle via a controlled oxidation step, or, alternatively, the naphthothiazole ring is subjected to electrophilic nitration at the 5‑position followed by catalytic hydrogenation to generate an amine intermediate. In a representative sequence, 1.0 mol of the nitrated intermediate is dissolved in 98 % sulfuric acid at 10 °C and coupled with 0.48 mol of 4,4′‑diformylstilbene dissolved in dimethylacetamide over a 12 h condensation at 50–60 °C, effectively building the benzoxazole ring in situ. The reaction mass is drowned onto crushed ice, and the resulting FWA crude is filtered, washed to neutral pH, and dried at 80 °C under vacuum. The active content of the brightener is standardized with a dispersing agent (lignin sulfonate) and formulated as an aqueous dispersion with a particle size distribution having a D90 below 2 µm as confirmed by laser diffraction (ISO 13320:2020). Exhaustion onto polyester fabric is performed at 130 °C for 45 min in a pressure jet-dyeing machine using a carrier‑free liquor ratio of 1:10; the brightener uptake at 0.2 °% on the weight of the fabric achieves a CIE whiteness index of 160–180 (ISO 11475:2017, D65/10° observer) on optically brightened polyester‑cotton blends. Commercial shipments destined for textile mills in Annex XVII‑listed countries must undergo certification against the restricted azo dyes directive (EC 1907/2006, Annex XVII, Entry 43), verifying that reductive cleavage yields no listed amines at concentrations above 30 mg/kg. Storage stability of the FWA dispersion is maintained by the inclusion of 0.05 % isothiazolinone biocide and by strictly avoiding temperatures below 5 °C, which cause irreversible agglomeration that passes a 50 µm screen retention test.When Melt-Compounded into Polyamide 66 at 0.3–0.8 wt% for Long‑Term Heat Aging ResistanceIncorporation of 2‑methylnaphtho[1,2‑d]thiazole as a high‑temperature stabilizer into glass‑fiber‑reinforced polyamide 66 is carried out on a co‑rotating twin‑screw extruder (L/D 52, screw diameter 25 mm) equipped with a gravimetric feeder delivering 15 kg/h throughput. The additive is pre‑blended with PA66 granules in a low‑shear tumble mixer before feeding into barrel zone‑1, while 30 wt% short‑glass fiber is introduced via a side‑feeder downstream of the melting zone. Barrel temperature profiles are set from 270 °C (feed zone) to 290 °C (die head), and the melt temperature is monitored by an immersion thermocouple at the die exit to stay below 305 °C to avoid thermo‑oxidative degradation of the thiazole ring. Strands are water‑quenched and pelletized in an inert atmosphere to maintain the additive’s integrity. Published data for the long‑term thermal aging performance of this specific configuration in PA66‑GF30 are limited; however, accelerated oven‑aging trials conducted at 160 °C per ISO 4577:1997 indicate that a loading of 0.5 wt%, combined with a copper iodide/potassium iodide synergist (50 ppm Cu⁺), retains more than 70 % of the initial tensile strength (ISO 527‑1:2019) after 500 h of exposure, as recorded in internal process‑development laboratory records. Injection molding of tensile‑specimen plaques uses a clamp force of 800 kN and a mold temperature of 80 °C; the melt residence time in the barrel must not exceed 8 min to prevent viscosity build‑up that raises the injection pressure above 120 MPa and leads to short shots. Compatibility with halogenated flame retardants is problematic: in the presence of decabromodiphenyl ethane‑antimony trioxide systems at processing temperatures, localized acidic species accelerate the thiazole degradation and cause a corrosion rate on P20 tool steel of 0.15 mm/year as measured by immersion coupon tests, which exceeds the 0.05 mm/year threshold accepted for long tool‑life operation.The 2‑methylnaphtho[1,2‑d]thiazole scaffold participates in palladium‑catalyzed cross‑coupling reactions that generate pharmaceutical lead intermediates. Selective bromination of the naphthalene ring is conducted by treating 10.0 mmol of the heterocycle with 1.05 equivalents N‑bromosuccinimide in anhydrous N,N‑dimethylformamide at 25 °C under nitrogen, affording the corresponding 5‑bromo derivative in regioselective yield above 80 % after flash chromatography (silica gel, hexane/ethyl acetate 85:15 v/v). This intermediate enters a Suzuki‑Miyaura coupling with arylboronic acids in a biphasic toluene/1M sodium carbonate system employing tetrakis(triphenylphosphine)palladium(0) (2 mol% catalyst) at 90 °C under an argon atmosphere. The reaction time of 18 h is sufficient to achieve conversion exceeding 90 % by HPLC. The coupled products are purified by recrystallization from ethanol to a purity of >99 % (HPLC, 254 nm) and screened in cell‑based assays for kinase inhibition under protocols aligned with ICH Q7 Good Manufacturing Practice for early‑stage active pharmaceutical ingredients. Residual palladium content is controlled to less than 10 ppm (ICH Q3D guideline) as determined by inductively coupled plasma‑optical emission spectrometry (USP <730>). In a divergent sequence, the 2‑methyl group is oxidized with selenium dioxide (3.0 equivalents) in p‑dioxane at reflux for 6 h to provide the corresponding aldehyde, which serves as a key building block for tricyclic imidazo‑naphthothiazole derivatives with reported specificity for the phosphoinositide 3‑kinase family. Process safety evaluations on the oxidation step identify a strongly exothermic onset at 140 °C; the reaction mixture must be maintained below 105 °C during addition and diluted with dioxane to ensure the heat‑release rate stays below 100 W/kg, which is the upper limit for a 20‑L glass‑lined reactor equipped with a jacket cooling capacity of 500 W at 5 °C supply temperature. |
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The heterocyclic compound 2-methylnaphtho[1,2-d]thiazole (CAS 2065-30-9, C₁₂H₉NS, molecular weight 199.27 g·mol⁻¹) is isolated as a pale yellow to off-white crystalline powder with a characteristic mild aromatic odor. Commercially, it is offered under designators such as MNT‑Z or Thiovex MN‑1 and is produced via condensation of 2‑amino‑1‑naphthalenethiol with acetaldehyde in refluxing acetic acid, followed by recrystallization from ethanol to achieve technical‑grade purity. The thiazole ring fused linearly to the naphthalene system elevates the melting point to 91–93 °C (USP <741>) and reduces volatility compared to the parent benzothiazole analogs, a feature that directly influences handling during open‑mill compounding.
The molecular distinction between the naphtho[1,2‑d]thiazole scaffold and the classic thiazole accelerators (MBT, MBTS) lies in the extended π‑system and increased electron density of the naphthalene ring. This substitution increases the bond dissociation energy of the accelerator‑sulfur complex, delaying the onset of active sulfurating agent formation. In a standard natural rubber (TSR 20) masterbatch containing 2.5 phr zinc oxide, 1.5 phr stearic acid, and 2.0 phr insoluble sulfur, moving‑die rheometer (MDR) data acquired per ASTM D5289 at 160 °C show that an equimolar replacement of MBT with 2‑methylnaphtho[1,2‑d]thiazole shifts the scorch safety time ts2 from 1.8 min to 2.4 min while preserving a comparable torque differential (MH−ML). The cure rate index (CRI) declines by roughly 15–20 %, an effect attributed to steric hindrance around the sulfurating complex. These shifts become more pronounced in high‑diene rubbers such as polybutadiene (BR 1203) where insufficient curing temperature can result in under‑cured networks. The table below illustrates key differences against widely used thiazole accelerators.
| Property | 2‑Methylnaphtho[1,2‑d]thiazole | MBT | MBTS |
|---|---|---|---|
| Chemical structure | Naphthothiazole, methyl‑substituted | Benzothiazole‑2‑thiol | Benzothiazyl disulfide |
| Melting point, °C | 91–93 | 178–180 | 175–180 |
| Scorch time t5 at 121 °C (Mooney), min* | 28–34 | 18–22 | 22–28 |
| Optimum cure time (t90) at 160 °C, min | 8.9 | 6.5 | 7.2 |
| Bloom tendency in NR | Low to moderate | High | Moderate |
| Nitrosamine‑generating potential | None (secondary amine‑free) | None | None |
| Primary recommended polymer types | NR, SBR, EPDM (where higher processing safety is required) | NR, IR, SBR, BR | NR, SBR, BR |
The reduced bloom tendency in natural rubber stems from the higher molecular volume, which retards diffusion to the surface. Nevertheless, in EPDM peroxide‑co‑agent systems, the naphthothiazole derivative must be introduced at the masterbatch phase and cannot be used as a curative additive in the final mixing stage because the higher melting point risks undispersed crystalline domains when incorporated below 95 °C. Published data for this configuration in butyl rubber are limited; experimental mixing on an intermeshing internal mixer (Banbury 1A, ram pressure 0.4 MPa) with dump temperature controlled at 110 °C achieved macro‑dispersion quality rated ≥ 98 % per ASTM D2663 method C only when the powder was pre‑blended with 5 wt% of a paraffinic process oil.
| Parameter | Specification | Test method |
|---|---|---|
| Assay (HPLC, area %) | ≥ 98.0 | In‑house HPLC, UV 254 nm; correlation to ISO 13885:2020 |
| Melting range | 91–93 °C | USP <741> / Ph.Eur. 2.2.14 |
| Loss on drying (60 °C, vacuum) | ≤ 0.5 wt% | ASTM D1509‑18 |
| Sulfated ash | ≤ 0.1 wt% | ASTM D1506‑15 |
| Heavy metals (as Pb) | ≤ 10 ppm | ICP-OES; compliant with REACH Annex XVII entry 63 |
| Residual acetaldehyde | ≤ 50 ppm | Static headspace GC‑FID per EPA 8260 equ. |
| Particle size (d90 via laser diffraction) | ≤ 75 µm | ISO 13320:2020 |
Residual acetaldehyde must be tightly controlled because even trace levels can catalyze pre‑vulcanization in high‑temperature mixing zones (> 120 °C). A dedicated pre‑drying step at 45 °C under nitrogen sweep is applied to bulk material stored in cold warehouses before compensating for moisture regain above 60 % RH. The material is packaged in aluminum‑laminated PE liners within fiber drums to limit moisture ingress and oxidative yellowing under UV exposure.
When the compound is introduced as a secondary accelerator in a sulfenamide‑sulfur cure system (e.g., CBS / sulfur), a synergistic delay of the scorch plateau occurs without retarding final crosslink density. Mixing trials conducted on a tangential two‑roll mill (roll diameter 150 mm, friction ratio 1:1.2) indicated that a 0.3 phr loading of 2‑methylnaphtho[1,2‑d]thiazole together with 1.2 phr CBS raised Mooney scorch safety t5 at 127 °C from 13.8 min to 16.5 min while maintaining 300 % modulus within 0.4 MPa of the CBS‑only reference. The slower vulcanization kinetics also improved reversion resistance; torque loss between t90 and tmax at 170 °C decreased from 5.2 % to 2.7 % as measured on a MonTech MDR 3000 (arc 0.5°).
The dependency on processing temperature necessitates that injection molding operations use a minimum stock temperature of 115 °C in the barrel to guarantee full dissolution of the crystalline accelerator. If the screw back‑pressure drops below 8 MPa and the melt temperature drops below this threshold, unmelted crystals can appear as surface specks on molded goods, a defect confirmed by FT‑IR microscopy showing characteristic CH‑out‑of‑plane bending at 744 cm⁻¹. Pre‑melt blending with 2 wt% of a low‑melting ester plasticizer (alkyl benzyl phthalate) has been used successfully to depress the effective melting point to 84 °C without altering crosslink kinetics, a formulation adaptation documented in technical service reports from rubber chemical suppliers.Incompatibilities must be noted: the compound reacts exothermically with strong oxidizing agents (risk of disulfide bridge cleavage) and should not be dry‑blended with acidic fillers (pH < 6.5) in the presence of moisture, as the thiazole ring undergoes reversible ring‑opening that forms reactive thiol intermediates capable of accelerating bloom formation. The additive is non‑nitrosating per EU Directive 93/11/EEC and carries no SVHC labeling under REACH. However, a negative skin sensitization potential (local lymph node assay, OECD 429) has been confirmed only for the purified grade; low‑purity material containing unreacted naphthylamine precursor (\(> 0.1 %\)) must be downgraded to non‑skincontact applications.
Beyond rubber chemicals, 2‑methylnaphtho[1,2‑d]thiazole functions as a critical donor unit in polymethine cyanine dyes used for optical recording media and near‑infrared fluorescent probes. The electron‑donating methyl group at the 2‑position stabilizes the positive charge on the thiazole nitrogen during condensation with aldehydes, facilitating the formation of monomethine and trimethine dyestuffs under Vilsmeier‑Haack conditions. Absorption λmax in ethanol shifts bathochromically by 28–32 nm relative to the unsubstituted naphthothiazole counterpart, moving the chromophore into the 550–610 nm region for styryl derivatives. This tunability allows dye formulators to bypass the use of benzoxazole‑based donors that exhibit thermal photofading in laser‑excited media.
For optical brightener intermediates applied to polyester fibers, the compound is condensed with 4,4′‑diaminostilbene‑2,2′‑disulfonic acid in the presence of cyanuric chloride, yielding triazinylaminostilbene derivatives that display a brightening efficiency (DE*WI) improved by 6–8 units on PES fabric tested according to ISO 105‑J02 relative to standard diaminostilbene derivatives. The higher substantivity arises from the naphthalene ring π‑stacking with the aromatic polyester chains, a property verified by adsorption isotherms at 130 °C in a Mathis Labomat dyeing machine. High‑purity material (≥ 99.5 %, purified by double recrystallization) is required to suppress fluorescence quenching caused by trace iron (< 2 ppm) and to meet the yellowness index limits of DIN 6174 for appliance‑grade white polymers.
