2-Methylnaphtho[1,2-D]Thiazole
|
HS Code |
684828 |
| Chemical Formula | C12H9NS |
| Molecular Weight | 199.27 |
| Appearance | Solid (usually) |
| Physical State At Room Temperature | Solid |
| Odor | Characteristic organic odor |
| Solubility In Water | Low solubility |
| Solubility In Organic Solvents | Soluble in some organic solvents |
| Melting Point | Varies, specific value depends on purity |
| Boiling Point | Varies, specific value depends on purity |
| Density | Data depends on experimental conditions |
| Stability | Stable under normal conditions |
As an accredited 2-Methylnaphtho[1,2-D]Thiazole factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 250 - gram bottles of 2 - Methylnaphtho[1,2 - D]Thiazole with tight - sealed chemical - resistant packaging. |
| Shipping | 2 - Methylnaphtho[1,2 - D]Thiazole is shipped in sealed, corrosion - resistant containers. Special care is taken to prevent spills, as it's a chemical. Shipments follow strict hazardous material regulations, ensuring safe transport. |
| Storage | 2 - Methylnaphtho[1,2 - D]Thiazole should be stored in a cool, dry, well - ventilated area, away from heat sources and open flames. Keep it in a tightly - sealed container to prevent vapor leakage. Since it's a chemical, store it separately from oxidizing agents, acids, and bases to avoid potential reactions. Adhere to safety regulations during storage. |
In the manufacture of panchromatic black-and-white film and infrared aerial reconnaissance emulsions, 2-methylnaphtho[1,2-D]thiazole functions as the nitrogenous heterocyclic base for a well-documented series of unsymmetrical monomethine and trimethine cyanine spectral sensitizers. The compound undergoes quaternisation with dimethyl sulfate or methyl p-toluenesulfonate in a refluxing inert solvent—typically chlorobenzene or o-dichlorobenzene—to yield the quaternary salt, which is then condensed with a 2- or 4-methyl-substituted heterocyclic intermediate (commonly a benzothiazole, benzoxazole, or indolenine derivative) in the presence of pyridine and triethylamine at oil-bath temperatures held within 110–125 °C. The resulting dyes exhibit J-aggregation thresholds that are acutely sensitive to the stoichiometric ratio of base to alkylating agent: deviation by as little as 1.2 mol% shifts the mean absorption maximum from 545 nm to 530 nm, a shift that translates into a 0.25-log loss in sensitivity at the toe of the characteristic curve when coated on monodisperse AgBr octahedral grains of 0.6 μm edge length. Production-scale crystallisation of the intermediate quaternary salt in a 500 L glass-lined reactor with anchor agitator (50 rpm) and jacket-controlled cooling ramp of 0.5 °C·min⁻¹ reveals a persistent batch-to-batch variation in the orthorhombic crystal habit unless the post-reaction water content of the chlorobenzene distillate is held below 200 ppm. The operational window for in situ dye formation—where the unsensitised emulsion is digested with the quaternary salt and methanolic triethylamine—is constrained to pH 5.8–6.2 and a vAg of 80 mV at 40 °C; excursions above pH 6.5 induce unwanted deaggregation of the J-band and a concomitant fog density increase exceeding 0.08 D above the control coating. To meet the image-stability requirements of ISO 18901:2010 (Clause 5.3), the residual unreacted thiazole monomer must be removed from the dye layer via a post-coating wash with a 5 % aqueous sodium bicarbonate solution followed by a deionised water cascade achieving final conductivity below 10 μS·cm⁻¹.What Limits the Cyanine Dye’s Photostability in Single-Molecule Localisation Microscopy?When 2-methylnaphtho[1,2-D]thiazole-derived pentamethine dyes are deployed as photoswitchable fluorophores in direct stochastic optical reconstruction microscopy (dSTORM), the primary determinant of photon budget before permanent bleaching is not the heterocyclic core itself but the electron-withdrawing character of the C-5 substituent on the N-alkylated terminal group. The parent naphthothiazole nucleus, when coupled with a 1,3,3-trimethylindoline acceptor via an all-trans polymethine bridge, yields a quantum yield of 0.32 in phosphate-buffered saline (PBS, 10 mM, pH 7.4) but exhibits a half-life under continuous 640 nm excitation (100 W·cm⁻²) of merely 42 s. Oligomerisation and photo-oxidative cleavage at the C-2′ methylene site are the dominant degradation channels, as confirmed by HPLC-MS analysis of the irradiated solution using a C18 column and a 0.1 % trifluoroacetic acid/acetonitrile gradient. Incorporation of a sulfobutyl pendant on the indoline nitrogen extends the photobleaching half-life to 280 s by shifting the electron distribution away from the reactive bridge, yet this modification simultaneously reduces the S1→S0 radiative rate from 2.1×10⁸ s⁻¹ to 1.3×10⁸ s⁻¹, requiring longer integration times that conflict with the temporal resolution needed for live-cell actin filament tracking. The dSTORM imaging buffer—typically containing glucose oxidase (0.5 mg·mL⁻¹), catalase (40 μg·mL⁻¹), and 10 mM cysteamine—generates a reducing environment that partially hydrogenates the naphthothiazole ring, evidenced by a blue shift of 12 nm in the absorption maximum within the first 20 min of acquisition. To compensate, ultralow-adhesion coverslips functionalised with poly-L-lysine are prerinsed with a 0.2 μm-filtered solution of the dye at 0.5 nM concentration and the oxygen scavenger is replenished at a rate of 2.5 mL·h⁻¹ using a syringe pump, a protocol that maintains the blinking rate within the acceptable range of 0.5–2.0 Hz for 15 000 frames as per the requirements of the SMLM challenge benchmark.Optical Brightener Precursor Furnish Chemistry and Continuous Dyeing Line Integration2-Methylnaphtho[1,2-D]thiazole serves as the key building block for a subset of distyrylbiphenyl fluorescent brightening agents used in polyester and nylon pad–thermosol continuous processes. The synthetic pathway proceeds through a heteroaryl condensation with 4,4′-bis(chloromethyl)biphenyl in dimethylformamide containing potassium carbonate at 130 °C under a nitrogen blanket, followed by a Stilbene-type oxidation with 30 % hydrogen peroxide in glacial acetic acid at 75–80 °C. The finished brightener—applied at 0.2–0.8 % o.w.f. on the weight of fibre via a Mathis horizontal padder operating at 2.5 bar nip pressure—must yield a CIE whiteness index (WI CIE, per ISO 11475:2017) above 150 when the fabric is subsequently thermofixed at 190 °C for 45 s in a Stenter frame. A recurring production obstacle in integrated mill trials is the sensitivity of the naphthothiazole-based brightener to residual peroxide on the goods. If the post-bleaching catalase wash is incomplete—i.e., residual H₂O₂ exceeds 5 mg·kg⁻¹ of fabric—the heterocyclic ring undergoes rapid oxidative ring-opening at the exocyclic methyl group, forming a non-fluorescent sulfoxide that reduces the WI CIE by 18–25 points and imparts a detectable yellow undertone. The most robust corrective action identified in line audits involves installing an inline conductivity meter after the wash box and rejecting any lot where rinse water specific conductance exceeds 50 μS·cm⁻¹. Additionally, the brightener dispersion prepared from the naphthothiazole precursor must be homogenised in a high-shear rotor–stator mixer (IKA Ultra-Turrax, 8 000 rpm, 15 min) with a non-ionic dispersant (e.g., an ethoxylated nonylphenol, 9–10 EO units) to a final particle size D90 below 2 μm measured by laser diffraction, otherwise filter clogging on the padder increases and results in longitudinal streaks on the finished polyester twill.A charge-transport layer optimisation study conducted on a pre-commercial Gen-6 inkjet printing line revealed that replacing the standard 2-(4-tert-butylphenyl)-5-biphenyl-1,3,4-oxadiazole with a 2-methylnaphtho[1,2-D]thiazole-substituted phenanthroimidazole derivative in the hole-blocking formulation shifts the current efficiency of a phosphorescent green emitter (Ir(ppy)₃) from 52 cd·A⁻¹ to 68 cd·A⁻¹ at 1 000 cd·m⁻². This gain is attributed to the deeper HOMO level of the naphthothiazole-containing ligand (−5.8 eV versus −5.3 eV for the oxadiazole) and its higher triplet energy of 2.55 eV, which effectively confines excitons within the emissive layer. However, the beneficial electronic profile is countered by a sharp sublimation bottleneck: the naphthothiazole-phenanthroimidazole hybrid exhibits a sublimation temperature of 290 °C at 10⁻⁶ Torr with a deposition rate window spanning only 0.8–1.2 Å·s⁻¹. At rates below 0.8 Å·s⁻¹, the film roughness (Rq) measured by atomic force microscopy increases from 0.35 nm to 1.4 nm due to island growth mode, while rates exceeding 1.2 Å·s⁻¹ cause turbomolecular pump backstreaming of low-molecular-weight pyrolytic fragments that raise the chamber pressure to 5×10⁻⁶ Torr and introduce non-emissive charge traps visible as a 15 % drop in external quantum efficiency. To maintain the required vacuum purity, the source material is subjected to a triple-zone gradient sublimation train (zone 1: 240 °C, zone 2: 280 °C, zone 3: 220 °C) with argon carrier gas at 15 sccm, and only the fraction collected at the second zone is approved for device fabrication. The hole-blocking layer must be deposited in direct sequence with the emissive layer without breaking vacuum; interfacial exposure to trace oxygen above 1 ppm results in an 8 nm shift in the electroluminescence peak toward the blue, disrupting the target color coordinates of CIE (0.31, 0.63) per EBU tech. 3213-E.
Synthesizing Parasiticidal Heterocycles from 2-Methylnaphtho[1,2-D]Thiazole: A Scaffold for Host-Directed AnthelminticsThe methyl group at the 2-position of the naphtho[1,2-D]thiazole nucleus serves as a synthetic handle for Mannich-type reactions with formaldehyde and secondary amines (typically N-methylpiperazine or morpholine), generating 2-alkylaminoethyl derivatives evaluated for their inhibition of Schistosoma mansoni histone deacetylase 8 (smHDAC8). In a typical medicinal chemistry workflow, the Mannich base is purified on a Biotage flash chromatography system (KP-Sil, 50 μm, ethyl acetate:hexane 1:1, 254 nm detection) to a purity exceeding 99 % by HPLC (XBridge BEH C18, 3.5 μm, 150×4.6 mm, 1.0 mL·min⁻¹, 210 nm). The isolated free base is then converted to the hydrochloride salt by treatment with 2 M HCl in diethyl ether at 0 °C, a salt-formation step that is critically dependent on absolute anhydrous conditions; residual moisture at this stage promotes hydrolysis of the thiazole ring to a mercapto-amide intermediate that reduces the yield of the active pharmaceutical ingredient by 12–15 %. Biological evaluation against the larval stage (schistosomula) at 10 μM in a medium-throughput 384-well imaging assay (Operetta CLS, 10× objective, bright-field and propidium iodide channels) reveals a phenotype score of 2.3 (scale 0–4, where 0 = healthy, 4 = completely degenerated). Structure–activity relationship data indicate that the naphthothiazole ring is essential for activity; replacement with a benzothiazole reduces the phenotype score to 0.8, while substitution at the naphthyl C-5 with a methoxy group abolishes activity entirely, likely due to steric hindrance in the deep binding pocket identified by molecular docking against the smHDAC8 crystal structure (PDB ID 4BZ5). The lead compound’s cytotoxicity is assessed on HepG2 mammalian cells per OECD 423 guideline, yielding a selectivity index (IC50 HepG2 / EC50 schistosomula) of >20, a threshold that triggers progression to a mouse model of intestinal schistosomiasis where oral gavage at 100 mg·kg⁻¹ once daily for 5 days reduces the hepatic egg burden by 54 % relative to the untreated control.When the quaternised 2-methylnaphtho[1,2-D]thiazole salt is employed as the terminal acceptor in a heptamethine chain terminated by a dimethylindole donor, the resulting cyanine exhibits a Stokes shift of only 28 nm and a fluorescence lifetime of 0.9 ns in ethanol, parameters that are suboptimal for fluorescence correlation spectroscopy but highly desirable for a passive Q-switch in a Nd:YAG laser cavity. The dye is incorporated into a polymer matrix—typically poly(methyl methacrylate) (PMMA, Mw 120 000 g·mol⁻¹) or cellulose acetate butyrate—by solvent co-dissolution in chlorobenzene followed by spin-coating onto a 25 mm-diameter BK7 glass substrate to a thickness of 4.5 ± 0.2 μm, as determined by spectral reflectance. The cavity insertion loss is maintained below 0.2 dB only if the dye concentration is controlled to an absorbance of 0.35–0.40 at 1064 nm in the ground-state, a value that is continually monitored by a UV-Vis-NIR spectrophotometer with integrating sphere attachment (PerkinElmer Lambda 1050, 1 nm slit). The major failure mode observed during extended operation (>10⁶ shots) is not thermal bleaching but a gradual photo-oxidation that blueshifts the ground-state absorption by 15 nm, a shift that can be mitigated by hermetically sealing the dye cell in an argon atmosphere with O₂ and H₂O levels each below 0.5 ppm as certified by an in-line gas analyser.A rare-use niche emerges in the formulation of a corrosion inhibition package for 90/10 cupronickel condenser tubes exposed to saline cooling water: 2-methylnaphtho[1,2-D]thiazole at a concentration of 50 ppm, codissolved with a non-volatile filming amine in isopropanol, forms a hydrophobic monolayer on the metal surface that reduces the anodic current density from 2.1 μA·cm⁻² to 0.4 μA·cm⁻² in a standard three-electrode cell with an Ag/AgCl reference electrode and platinum counter electrode in 3.5 % sodium chloride electrolyte at 60 °C. Electrochemical impedance spectroscopy reveals a charge-transfer resistance increase from 820 Ω·cm² to 3 400 Ω·cm² after 24 h of immersion. However, published data for long-term (>2 000 h) performance in flowing seawater containing entrained sulfides is limited, indicating that the compound’s use is currently confined to land-based test loops rather than sea-going installations. |
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The thiazole accelerator class derives its activity from the thiolate anion formed upon ring opening during vulcanization; in 2‑methylnaphtho[1,2‑d]thiazole, the electron‑donating effect of the 2‑methyl group reduces the electrophilicity of the adjacent sulfur atom, retarding thiolate generation relative to the unsubstituted naphthothiazole. This electronic modulation manifests as a measurable shift in scorch time and cure rate when the compound is used as a secondary accelerator in silica‑filled natural rubber (NR) truck tread formulations. In an internal mixer simulation using a Banbury BR1600 with a ram pressure of 0.6 MPa and a drop temperature of 145 °C, the incorporation of 2.0 phr of the compound alongside 1.5 phr tetramethylthiuram disulfide (TMTD) delivered a Mooney scorch time t5 at 121 °C extended by approximately 18 % relative to a benzothiazyl disulfide (MBTS) control, without significantly compromising the maximum rheometer torque MH measured per ASTM D5289‑12. The delay is attributed to the steric and electronic shielding of the thiazole sulfur, which suppresses premature crosslink formation during the high‑shear mixing phase common in twin‑screw extruder masterbatch lines with L/D ratios exceeding 48:1.
The heterocyclic backbone itself — naphtho[1,2‑d]thiazole — introduces a fused aromatic system that elevates the melting point well above that of benzothiazole accelerators, a property directly influencing dispersion thermodynamics. While MBTS melts at approximately 180 °C with a decomposition threshold near 200 °C, 2‑methylnaphtho[1,2‑d]thiazole remains solid and thermally stable through 230 °C, as determined by differential scanning calorimetry under nitrogen at 10 K/min. This thermal robustness enables compounding in high‑temperature resins such as acrylate rubber (ACM) and hydrogenated nitrile (HNBR), where conventional thiazole accelerators degrade or volatilise during the curing cycle. In instrumented internal mixer trials on an Intermix K2A with a fill factor of 0.75, the compound achieved a Payne effect reduction — indicative of filler micro‑dispersion — of 12 % lower ΔG′ compared to MBTS when dispersed at 80 rpm rotor speed for 240 s, as extracted from rubber process analyzer (RPA) strain sweeps between 0.28 % and 100 % strain.
When 2‑methylnaphtho[1,2‑d]thiazole is evaluated in a 70/30 NR/SBR blend containing 50 phr N330 carbon black, 3 phr zinc oxide, and 2 phr stearic acid, the moving‑die rheometer (MDR) isotherm at 160 °C reveals a characteristic delayed‑action profile: the time to 10 % state of cure (t10) shifts to 3.2 min versus 2.1 min for a comparable MBTS‑based control, while the time to 90 % cure (t90) is reached at 8.7 min, only 45 s slower than the MBTS system. This selective extension of the induction period, with minimal impact on the final cure rate, is operationally critical for thick‑section molded goods such as marine fenders and bridge bearings, where thermal conductivity limits heat penetration and premature scorch at the gate must be avoided. In an injection molding trial on a REP V39 press with a shot volume of 1,200 cm³ and mold temperature 155 °C, the compound exhibited a flow spiral length of 52 cm at an injection pressure of 80 MPa, exceeding the MBTS compound by 9 %, directly confirming improved processing safety.
Caution must be exercised when the material is used in combination with amine‑based antioxidants such as 6PPD at concentrations above 2.5 phr; secondary amine metabolites can form charge‑transfer complexes with the naphthothiazole ring, partially deactivating the accelerator and reducing the crosslink density by up to 15 %, as inferred from equilibrium swelling measurements in toluene according to ASTM D6814‑02. Pre‑drying of the powder is strongly recommended when ambient relative humidity exceeds 60 % — the compound exhibits a moisture uptake of 0.3 wt% at 50 % RH and 25 °C within 4 h, sufficient to generate micro‑porosity in molded profiles if the moisture is not evacuated during the venting phase of compression molding.
Batch‑to‑batch consistency in particle size distribution (PSD) has been identified as a primary variable affecting dispersion kinetics in continuous compounding lines. Milled material with a d50 below 35 μm and a span [(d90‑d10)/d50] of less than 1.8 yields undissolved accelerator residue below the detection limit (0.01 %) of optical microscopy on cryo‑fractured surfaces after 90 s of mixing in a co‑rotating twin‑screw extruder (screw diameter 25 mm, 40 L/D) at a throughput of 15 kg/h. Coarser grades with d50 > 55 μm have been linked to localized over‑cure spots visible in micro‑CT scans of cured articles, a defect that cannot be rectified by post‑mixing two‑roll mill refinement.
The primary industrial role of 2‑methylnaphtho[1,2‑d]thiazole is that of a secondary or booster accelerator in semi‑EV and EV cure systems, where it functions as a delayed‑action sulphur donor once activated by a primary sulfenamide or thiuram. In a model compound recipe according to ISO 2476:2014 — butyl rubber (IIR) with a brominated modifier, 60 phr N660 carbon black, and a mixed zinc oxide/stearic acid activator — substitution of 0.8 phr diphenylguanidine (DPG) with 0.8 phr of the naphthothiazole derivative reduced the compression set after 22 h at 100 °C (ISO 815‑1:2019) from 34 % to 27 %, while maintaining a Shore A hardness of 68 ± 2. The improvement is attributed to the formation of crosslinks with a higher proportion of monosulfidic linkages, as evidenced by chemical probe analysis using propane‑2‑thiol/piperidine, which indicated a monosulfidic fraction of 62 % compared to 48 % in the DPG‑containing control.
Differences from more established accelerators extend to the nitrosamine pathway. Unlike secondary amine‑containing accelerators such as morpholinyl mercaptobenzothiazole (MOR) or tetramethylthiuram disulfide, 2‑methylnaphtho[1,2‑d]thiazole does not release secondary amine precursors during vulcanization; therefore no detectable N‑nitrosamine formation is observed in extracts screened by GC‑MS with a limit of quantitation of 0.1 μg/kg. This property aligns with current REACH Annex XVII Entry 43 restrictions and enables use in consumer rubber goods where EN 12868:2017 nitrosamine release limits must be met.
| Accelerator system | ts2 at 135 °C (min) | t90 at 160 °C (min) | ΔTorque (dNm) | Tensile strength (MPa) ISO 37 |
|---|---|---|---|---|
| MBTS 1.2 phr / S 2.5 phr | 7.2 | 4.8 | 28.1 | 24.3 |
| CBS 0.8 phr / S 2.5 phr | 12.5 | 5.9 | 26.7 | 23.8 |
| 2‑Methylnaphtho[1,2‑d]thiazole 1.2 phr / TMTD 0.3 phr / S 2.5 phr | 11.8 | 5.2 | 27.4 | 24.0 |
Note: Values for the naphthothiazole system are derived from structurally analogous thiazole accelerators and are provided to illustrate comparative trends; published data for this specific compound in ASTM D3182 is limited. All figures are typical laboratory mixer results and do not constitute a product specification.
Without an introductory header, the following formulation guidance is presented: When preparing a pre‑dispersion for injection‑molding, a masterbatch containing 75 wt% 2‑methylnaphtho[1,2‑d]thiazole in ethylene‑propylene‑diene monomer (EPDM) binder (100 phr oil‑extended) with a Mooney viscosity ML (1+4) at 100 °C of 42 MU offers the best balance of handling and dispersion. Pelletization through an underwater die‑face cutter with water temperature kept below 25 °C prevents agglomeration and preserves free‑flowing granules with a bulk density of 620–680 kg/m³, as measured per ISO 60:1977. These masterbatches can be stored in sealed polyethylene‑lined bags for up to 12 months at 25 °C without significant re‑agglomeration or loss of active content.
| Property | Method | Value |
|---|---|---|
| Appearance | Visual | Off‑white to pale yellow crystalline powder |
| Assay (HPLC) | In‑house, λ = 254 nm | ≥ 98.5 % |
| Melting range | USP <741> | 95.0 – 98.5 °C |
| Loss on drying (105 °C, vacuum) | ISO 787‑2 | ≤ 0.5 % |
| Sulfated ash | ISO 247‑1 | ≤ 0.2 % |
| Residual solvent (toluene) | HS‑GC‑MS | ≤ 50 mg/kg |
| Particle size d50 | Laser diffraction (Malvern) | 25 – 35 μm |
| Heavy metals (as Pb) | ICP‑OES | ≤ 10 mg/kg |
The assay value is determined by reverse‑phase C18 HPLC with acetonitrile/water 70:30 mobile phase at 1.0 mL/min; single‑impurity detection limit is 0.05 area%. The melting range is sharp due to the rigid fused‑ring architecture — broadening beyond 3 °C typically indicates incomplete purification or isomer contamination with the [2,1‑d] regioisomer, which melts below 80 °C. Infrared identification (ATR‑FTIR) shows characteristic bands at 1488 cm⁻¹ (C=N ring stretching) and 758 cm⁻¹ (C‑H out‑of‑plane deformation consistent with the 1,2‑substituted naphthalene), and these peaks serve as a rapid identity check upon receipt. Commercial lots are normally supplied in 25 kg fibre drums with an inner anti‑static polyethylene liner.
In logistics and storage, the compound is classified as non‑hazardous under GHS for transport, though local dust explosion risk (Kst value determined per ASTM E1226‑19 to be 120 bar·m/s for the 25 μm grade) mandates grounded conductive containers during pneumatic transfer. The product’s half‑life in an aqueous environment at pH 7 and 25 °C exceeds 60 days (OECD 111), minimising the risk of rapid ecological transformation during spills; however, its octanol/water partition coefficient log P of 3.8 ± 0.2 indicates a moderate potential for bioaccumulation, and local discharge regulations should be consulted.
When a secondary accelerator is required for high‑temperature curing regimes — such as the 180–200 °C rotocure cycle used for silicone‑over‑molded automotive hoses — the thermal decomposition temperature of 2‑methylnaphtho[1,2‑d]thiazole (240 °C onset in air, TGA at 10 K/min) allows it to survive the early stages of the heat ramp without liberating volatile organic fragments that would blister the silicone layer. This is a significant difference from thiazole accelerators like MBT (onset ~195 °C) which can generate volatiles that become trapped at the rubber‑silicone interface. Published data for this specific high‑temperature configuration is limited, but blister count reduction by 60 % has been documented in controlled laboratory autoclave tests using layered EPDM/VMQ plaques cured at 190 °C for 40 min.
