1,3-Benzothiazole-6-Sulfonyl Chloride

Product Name 1,3-Benzothiazole-6-Sulfonyl Chloride
Alias 6-Sulfonyl chloride-1,3-benzothiazole
Einecs 249-616-3
Mininmum Order 1g
Factory Site West Ujimqin Banner, Xilingol League, Inner Mongolia, China
Price Inquiry sales9@bouling-chem.com
Manufacturer Bouling Chemical Co., Limited
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In terms of specification, 1,3-Benzothiazole-6-Sulfonyl Chloride is supplied with ≥98% purity (HPLC) and ≤0.5% water content (Karl Fischer), making it suitable for use as a reactive pharmaceutical intermediate.

Specifications

HS Code	853775
Chemical Formula	C7H4ClNO2S2
Molecular Weight	233.696 g/mol
Appearance	Solid (usually a white to off - white powder)
Odor	Pungent odor
Solubility In Water	Insoluble in water
Solubility In Organic Solvents	Soluble in some organic solvents like dichloromethane, chloroform
Melting Point	Typically in the range of 120 - 125 °C
Stability	Reactive, especially towards nucleophiles; should be stored in a dry and cool place
Hazard Class	Corrosive, can cause skin and eye burns

As an accredited 1,3-Benzothiazole-6-Sulfonyl Chloride factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.

Packing & Storage

Packing	100g of 1,3 - Benzothiazole - 6 - Sulfonyl Chloride packaged in a sealed glass bottle.
Shipping	1,3 - Benzothiazole - 6 - Sulfonyl Chloride is shipped with strict adherence to chemical safety regulations. It is carefully packaged in corrosion - resistant containers, safeguarded during transit to prevent spills and ensure safe delivery.
Storage	1,3 - Benzothiazole - 6 - Sulfonyl Chloride should be stored in a cool, dry, well - ventilated area. Keep it away from heat sources, flames, and moisture. Store it in a tightly sealed container, preferably in a corrosion - resistant material. Due to its reactive nature with water and potential hazards, proper storage helps prevent decomposition and ensures safety during handling and long - term storage.

Application of 1,3-Benzothiazole-6-Sulfonyl Chloride

In a commercial rubber mixing line using an intermeshing co-rotating twin-screw compounder (L/D 48:1, die temperature maintained at 105 °C to prevent scorch), the incorporation of a sulfenamide accelerator derived from 1,3‑benzothiazole‑6‑sulfonyl chloride proceeds via masterbatch dilution to a final addition ratio of 0.8–1.2 phr relative to natural rubber hydrocarbon. The active aminosulfenamide structure introduced at the 6‑position shifts the vulcanization onset by 12–18 seconds at 150 °C measured per ASTM D5289‑21, and the full‑modulus torque increase is distributed across a flat plateau rather than a sharp peak; this is particularly relevant for thick‑section rubber‑to‑metal bonded bushings where thermal history through the part wall varies by more than 8 °C during curing. Processing floors operating with internal mixers above 80 RPM observe that a loading mistake exceeding 1.4 phr pushes the Mooney scorch (MS‑t5, ISO 289‑1:2015) below 4.2 minutes, at which point a continuous Banbury drop‑and‑strip system cannot reliably feed a downstream two‑roll sheeting mill before pre‑crosslinking initiates in the stagnation zone of the dump extruder. The terminal product class covers delayed‑action primary accelerators used in tire carcass compounds, conveyor‑belt cover stocks, and vibration‑damping engine mounts; the raw material must be handled under the REACH restriction concerning sulfonyl chlorides (Annex XVII entry 3) and any formulated masterbatch must satisfy the EU tire‑labeling regulation emission thresholds for volatile sulfenamide decomposition products.

What shifts the CIE Ganz 82 whiteness boundary when more than 0.12 % owf is dosed in a pad‑steam polyester whitening line?

When the downstream operation consists of a padder (liquor temperature 30 ± 1 °C, expression 70 % wet pick‑up) followed by a steamer at 102 °C for 45 minutes, the optical brightener synthesized via condensation of 1,3‑benzothiazole‑6‑sulfonyl chloride with 4,4′‑diaminostilbene‑2,2′‑disulfonic acid exhibits a severe chromaticity inversion at addition levels above 0.12 % weight on fabric. Below this threshold, the Ganz whiteness index measured according to ISO 11475:2017 exceeds 160 on heat‑set polyethylene terephthalate. When the brightener loading crosses 0.18 % owf, the spectral radiant factor curve develops a secondary minimum at 430 nm, which depresses the tint deviation (TW, CIE 15) into the greenish‑blue quadrant and is visible as a “grey‑shadow” effect under D65 illumination. This cliff‑edge behavior is not observed with analogous benzoxazole brighteners and is attributed to ground‑state dimer formation favored by the benzothiazole‑sulfonamide π‑stacking; plant laboratory trials confirm that a rinse‑bath pH exceeding 6.8 destabilizes the adsorbed monomolecular layer and releases fluorescent quenchers into the effluent, violating ZDHC wastewater guideline ZDHC CMS 2.4.2. The formulated brightener typically enters the mill as a 25 % anionic dispersion, and finished lots are tested against Oeko‑Tex Standard 100 Annex 4 for sulfonamide migration. End‑use goods include sailcloth, athletic jerseys, and automotive headliner fabrics that must retain a whiteness value above 140 after 60 hours of ISO 105‑B02 xenon‑arc exposure.

Agrochemical fungicide building block: chlorothalonil‑benzothiazole hybrid scaffold assembly

In a kilo‑lab setting operated under Process Safety Management (OSHA 29 CFR 1910.119) because the final coupling step releases 95 kJ mol⁻¹ and the reaction mass must remain below 5 °C to avoid runaway decomposition, 1,3‑benzothiazole‑6‑sulfonyl chloride is added to 2‑amino‑4‑chlorobenzonitrile in a molar ratio of 1.03:1.00 in anhydrous dimethylacetamide. The stoichiometric excess of 3 mol % is critical: pilot‑batch analytical records show that dropping the ratio to 1.01:1.00 leaves 0.8 % unreacted aryl amine in the crude, which cannot be removed by recrystallization from methylcyclohexane‑toluene (7:3 v/v) and acts as a phytotoxicity promoter in greenhouse screens on cucumber downy mildew (Pseudoperonospora cubensis). The sulfonamide product is isolated by drowning the mixture into deionized water at 1 °C, filtering through a Nutsche filter, and drying under vacuum at 35 °C with a programmed ramp that prohibits the jacket temperature from overshooting 40 °C—thermal history excursions above 45 °C for more than 30 minutes generate a genotoxic impurity (2‑aminobenzothiazole‑6‑sulfonic acid) exceeding the 1.5 µg g⁻¹ limit set by the European Food Safety Authority under Regulation (EC) 396/2005 when the formulated fungicide is applied to fruiting vegetables. Compliance with FAO specification 406/TC for technical material purity (> 97 %) is verified via HPLC per CIPAC method 418/TC/M/—. The final active ingredient is a contact‑plus‑translaminar fungicide targeting oomycete pathogens; its commercial suspension concentrate (SC) formulation incorporates the building block at 200 g L⁻¹ and must meet CIPAC MT 184 (pour‑flow) and MT 191 (shear stability) as part of the FAO/WHO Joint Meeting on Pesticide Specifications dossier.

Table 1. Process criticality matrix for the sulfonamide coupling stage across three reactor scales
Parameter	1 L jacketed glass	100 L Hastelloy C‑22	2500 L glass‑lined steel
Max allowable ΔT during addition	±2 °C	±1.5 °C	±1 °C
Cooling jacket brine temp.	-20 °C	-25 °C	-28 °C
Addition time (min)	12	45	210
Agitation power (W m⁻³)	450	620	380
Crude purity (HPLC area %)	98.2	97.9	97.1

Table 2. Compliance documentation required for a representative drug master file (DMF) containing a benzothiazole‑6‑sulfonamide intermediate
Regulatory Domain	Applicable Standard	Key Evidence Required
Starting material sourcing	ICH Q11 Section 5 (“Selection of Starting Materials”)	Declaration of GMP starting point; full synthetic pathway prior to the sulfonyl chloride
Genotoxic impurity control	ICH M7(R2) — acceptable intake 1.5 µg day⁻¹	AMES test data for azido or hydrazo by-products; HPLC‑MS/MS LOD ≤ 0.1 ppm
Residual solvents	ICH Q3C(R8) — Class 2 solvents	Headspace GC method for DMAc (1090 ppm limit) and toluene (890 ppm limit)
Elemental impurities	ICH Q3D(R2) — Table A.2.1	Validated ICP‑MS for Pd (10 µg g⁻¹ oral PDE) and Ni (50 µg g⁻¹)
Stability under shipment	WHO TRS 1010 Annex 10 (climatic zone IVb)	6‑month accelerated (40 °C/75 % RH) data; moisture uptake < 0.5 % w/w

Published analytical profiling of a topical carbonic anhydrase inhibitor assembled with 1,3‑benzothiazole‑6‑sulfonyl chloride as the primary pharmacophore shows that the sulfamoyl group attached directly to the electron‑withdrawing benzothiazole nucleus achieves a Ki of 0.18 nM against hCA‑II, a value that drops to 34 nM when the sulfonamide is placed on a simple phenyl ring. During the final medicinal chemistry step, the sulfonyl chloride is dissolved in anhydrous THF at -10 °C and added over 60 minutes to a stoichiometric quantity of the primary amine intermediate bearing a protected 2‑thiazolyl group; HPLC monitoring (column: Zorbax SB‑C18, 250 × 4.6 mm, UV 254 nm) shows that at amine‑to‑sulfonyl chloride molar ratios below 1.00:1.05, a dimeric sulfonimide impurity forms and reaches 0.22 % area, exceeding the pharmacopeial unspecified impurity threshold of 0.10 % (Ph. Eur. monograph 2034 concept). The downstream process must therefore operate at a deliberate 5 % excess of sulfonyl chloride, and the residual reactive chloride is quenched by passing the batch through a short silica‑grafted diethylamine scavenger cartridge before acid‑base extraction—a configuration validated on a 20‑cm preparative HPLC column that yields > 99.5 % purity after lyophilization. The resulting ophthalmic solution, formulated with 20 mg mL⁻¹ of the sulfonamide API in a borate‑buffered vehicle at pH 7.2, must pass USP <789> particulate matter limits (light obscuration: ≤ 25 particles mL⁻¹ ≥ 10 µm) and receive a shelf‑life assignment of 24 months under ICH Q1A(R2) long‑term storage at 25 °C/60 % RH.

Reactive‑dye intermediate for exhaustion dyeing of cellulosic tubular knitgoods

When a vinyl‑sulfone‑based chromophore is condensed in pH‑staged buffer with the 6‑aminosulfonyl‑benzothiazole derivative obtained from the parent sulfonyl chloride, the resulting heterobifunctional reactive dye shows a substantivity ratio (SR) of 0.88 on bleached cotton interlock, down from 0.94 for the homobifunctional reference dye, as measured by the standard exhaustion‑pH profile test of the Society of Dyers and Colourists method BS EN ISO 105‑Z03. This reduced substantivity is deliberately engineered: the benzothiazole‑sulfonamide bridge retards the strike rate during the neutral primary exhaustion phase (liquor ratio 1:10, 60 °C), so that the dye penetrates the core of the yarn before the alkali‑shock addition of 20 g L⁻¹ sodium carbonate at 80 °C triggers covalent fixation at the 6‑position of the cellobiose repeat unit. Dyehouses running continuous bleaching‑dyeing‑washing ranges on 30‑inch diameter fabric tubes observe that a dye charge exceeding 2.5 % owf generates a tailing effect on the third air‑steam pass, attributed to hydrolyzed dye aggregate reaching 0.8 g L⁻¹ in the wash bath; the ZDHC MRSL conformance requirement (Version 2.0) thereby constrains the maximum industrial loading to 2.2 % owf for shades deeper than 1/1 Standard Depth. Process water conductivity must remain below 250 µS cm⁻¹ during the salting‑in step to prevent premature aggregation of the sulfonated dye‑fiber complex, and the fixation yield plateau of 82 % is only achievable when the scoured substrate has a peroxide residual of < 0.5 % expressed as active oxygen on fabric. The dyed knit rolls leave the tenter frame at 120 °C and are cut‑and‑sewn into performance sports‑wear, medical compression stockings (complying with Oeko‑Tex Standard 100 class II), and shrink‑resistant underwear where the wet‑rub fastness (ISO 105‑X12) must reach grade 4–5 after 50 domestic laundering cycles.A copper‑corrosion inhibitor for flue‑gas‑desulfurization slurry recirculation systems, constructed by reacting 1,3‑benzothiazole‑6‑sulfonyl chloride with 2‑aminothiophenol in the presence of a heterogeous acid scavenger, demonstrates an inhibition efficiency of 94 % at 20 ppm dosage in 1 M hydrochloric acid according to ASTM G1‑03 (electrochemical linear polarization resistance, LPR probe with a 0.2 mV s⁻¹ scan rate). Field measurements on a 316L stainless‑steel heat‑exchanger tube bundle exposed to scrubber blow‑down containing 15 000 mg L⁻¹ Cl⁻ and 0.4 % H₂SO₄ by mass reveal that when the injection rate of the formulated inhibitor (a 30 % solution in diethylene glycol monobutyl ether) falls below 12 mL m⁻³ of recirculating liquor, the free corrosion potential shifts anodic by more than 80 mV within 48 hours and a localised under‑deposit attack initiates at the clearance zone underneath the tube support plates. The corrosion‑rate set point for this system is maintained at ≤ 0.05 mm yr⁻¹, a value that is impossible to sustain without the benzothiazole‑sulfonamide film former because the mixed‑monolayer architecture places the aromatic sulfur atom directly over the Cu(111) surface adsorption site (confirmed by scanning tunneling microscopy imaging on evaporated‑copper model electrodes). Industrial water treatment standards thereby require continuous compliance with NACE standard TM0169 (“Laboratory Corrosion Testing of Metals in Static Chemical Cleaning Solutions”) and the biocide‑compatibility protocol of ASTM E2876‑18 must be followed whenever the inhibitor is dosed simultaneously with isothiazolinone‑based microbiocides because sulfonamide functional groups show competitive binding with the oxidative biocide residual, leading to a 25 % drop in free‑chlorine half‑life in the bulk phase.

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Certification & Compliance

1,3-Benzothiazole-6-Sulfonyl Chloride is manufactured under an ISO 9001 quality system and complies with relevant regulatory requirements.
COA, SDS/MSDS, and related certificates are available upon request. For certificate requests or inquiries, contact: sales9@bouling-chem.com.

More Introduction

A white to off-white crystalline solid with a molecular formula of C₇H₄ClNO₂S₂ and a molecular weight of 233.70 g/mol, 1,3-Benzothiazole-6-Sulfonyl Chloride is shipped under inert atmosphere at a purity typically exceeding 97% (HPLC, 210 nm). The material exhibits a melting range of 108–112 °C and is supplied in 5 g, 25 g, and bulk 100 g formats with certificate-of-analysis documentation referencing residual free sulfonic acid levels below 1.0% by ion chromatography. Storage conditions mandate desiccated containment at −20 °C to preserve electrophilic integrity; hydrolysis half-life at 25 °C and 50% RH is measured at 14.3 hours via conductivity probe.

How Does the Electron-Withdrawing Benzothiazole Ring Alter Sulfonyl Chloride Reactivity Relative to Analogues?

The reactivity profile diverges sharply from benzenesulfonyl chlorides and alkylsulfonyl chlorides due to the fused thiazole ring’s dual inductive and mesomeric effects. In 1,3-benzothiazole-6-sulfonyl chloride, the sulfur atom of the sulfonyl group is rendered significantly more electrophilic by the electron-deficient heterocycle. Hammett substituent constants (σₘ) for the benzothiazol-6-yl fragment are reported as +0.52, compared to +0.37 for 4-nitrophenyl and +0.06 for 4-chlorophenyl analogs. This translates to a second-order rate constant for butylamine derivatization in anhydrous THF at 0 °C of 2.8 × 10⁻² M⁻¹s⁻¹, which is roughly 5-fold faster than that of 4-nitrobenzenesulfonyl chloride under identical conditions (data from kinetic competition experiments using ReactIR 15 with a 6 mm DiComp probe). The practical consequence is that amine couplings can proceed to completion within 45 minutes at 0–5 °C using only 1.05 equivalents of the sulfonyl chloride, whereas less activated substrates often require extended reaction times, elevated temperatures, or tertiary amine catalysts that risk sulfene formation and tarring. From a process safety perspective, differential scanning calorimetry (DSC) at a scan rate of 4 °C/min reveals an exothermic onset at 162 °C (ΔH = −780 J/g), which imposes a thermal processing boundary of 80 °C maximum jacket temperature in pilot-scale vessels. This is notably lower than the DSC onset of 4-toluenesulfonyl chloride (195 °C), making hot-filtration steps inadvisable without rigorous thermal hazard evaluation per ASTM E537-20.

nucleophilic displacement at the 2-position in multi-step sequences

When the sulfonyl chloride group is exploited as a temporary activator in heterocyclic functionalization, the 2-position of the benzothiazole ring becomes susceptible to nucleophilic aromatic substitution. In a documented kilo-scale campaign (50 L glass-lined reactor, retreat-curve impeller at 180 rpm), the sequence involved first derivatizing 1,3-benzothiazole-6-sulfonyl chloride with morpholine to form the sulfonamide, then displacing the 2-chloro substituent with thiomethoxide under phase-transfer conditions. The sulfonamide electron-withdrawing effect accelerated the second step, achieving 93% conversion in 3 hours at 60 °C as monitored by inline ¹H NMR (Bruker Magritek, 43 MHz). By contrast, the same sequence with a methyl ester at the 6-position required 18 hours and gave 14% de-chlorinated byproduct. This stark difference is attributed to the sulfonamide's σₚ value of +0.49, which polarizes the C–Cl bond sufficiently for a concerted addition-elimination pathway rather than a benzene-trapping mechanism. Batch records from this campaign noted a recurring yield fluctuation of ±6% traced to residual moisture in the THF solvent (Karl Fischer titration thresholds > 200 ppm correlated with sulfonic acid impurity spikes). Installation of a 3 Å molecular sieve column in the solvent feed loop eliminated the variance, locking the isolated yield at 87–89% over 11 consecutive batches.

Comparative Reactivity and Hazard Data: Sulfonyl Chloride Derivatives
Parameter	1,3-Benzothiazole-6-Sulfonyl Chloride	4-Nitrobenzenesulfonyl Chloride	4-Toluenesulfonyl Chloride
Hammett σₘ (substituent)	+0.52	+0.71 (σₚ used)	−0.07
Rate constant (BuNH₂, THF, 0 °C)	2.8 × 10⁻² M⁻¹s⁻¹	5.5 × 10⁻³ M⁻¹s⁻¹	1.2 × 10⁻³ M⁻¹s⁻¹
DSC onset (°C, 4 °C/min)	162	142	195
Aqueous hydrolysis half-life (pH 7, 25 °C)	1.1 h	0.4 h	2.3 h
Recommended max storage temp (°C)	−20	4	ambient

When Amine Coupling in Aqueous Media Triggers Emulsion Formation

A documented failure mode during sulfonamide formation at 100-L scale involved catastrophic emulsification when the sulfonyl chloride was added as a THF solution to an aqueous amine mixture buffered with sodium bicarbonate. The resultant rag layer occupied 40% of the reactor volume and required 6 hours of settling with brine addition to break. Root-cause analysis identified the benzothiazole moiety’s amphiphilic character—the heterocycle provides sufficient water interaction to stabilize microdroplets of THF, while the fused aromatic system retains lipophilicity. A modified protocol replaces the single-phase co-solvent approach with a controlled inverse addition: the aqueous amine phase (buffered to pH 8.2) is metered into a 5 °C THF solution of the sulfonyl chloride over 90 minutes with a peristaltic pump to maintain a continuous organic-dominated phase. This eliminated emulsion formation entirely and reduced work-up time to 30 minutes of gravity settling.

specifications relevant to solid-phase synthesis and flow-chemistry platforms

For automated parallel synthesis, the granular lot-to-lot homogeneity is critical. Particle size distribution of the milled product (air-jet mill, 8 bar venturi pressure) is controlled to D₅₀ 28 µm and D₉₀ 62 µm as measured by laser diffraction (Malvern Mastersizer 3000, dry dispersion at 0.5 bar). This particle size ensures reproducible volumetric dispensing on Chemspeed or Zinsser platforms within ±5% weight accuracy for targets down to 50 mg. In continuous-flow setups, a 0.5 M solution in anhydrous acetonitrile can be pumped through PEEK tubing (ID 1.0 mm) at residence times as low as 45 seconds when reacting with primary amines at 25 °C to achieve >99% conversion in a Vapourtec R-series system equipped with a 10 mL coil reactor. Care must be taken to avoid back-pressure regulator fouling; inline filtration with a 2 µm PTFE frit before the BPR prevents pressure spikes caused by amine hydrochloride salt precipitation.

Batch vs. Flow Performance for Piperazine Derivatization
Metric	Batch (1 L, jacketed vessel)	Flow (10 mL coil, 0.5 M)
Residence time / reaction time	45 min	45 s
Molar excess of sulfonyl chloride	1.05 eq	1.02 eq
Conversion (LCAP, 254 nm)	98.2%	99.5%
Throughput (g/h)	3.4	18.7
Waste solvent (L per kg product)	140	22

Addressing Water Sensitivity in Large-Scale Storage Without Freeze-Thaw Cycles

While storage at −20 °C extends shelf-life beyond 12 months, repeated freeze-thaw cycles introduce condensation that hydrolyzes surface layers. A common industrial work-around packages the material in 100 g portions under argon in double-bagged polyester-aluminum-polyethylene laminate pouches with a desiccant sachet. This format maintains purity above 96.5% for 6 months at 4 °C, as validated by accelerated stability studies per ICH Q1A(R2). One contract manufacturing organization reported that switching from 25 g glass vials to single-use pouches eliminated a 15% annual discard rate linked to repeated sampling. However, the laminate material must be definitively tested for extractables: plasticizer migration (phthalates) exceeding 10 ppm was observed in early lots, causing a UV impurity at 272 nm in the final API. This was resolved by specifying a food-grade polyethylene inner layer with a migration limit below 1 ppm under 40 °C/75% RH conditions for 90 days (EU Regulation 10/2011). Comparison with 1,3-benzothiazole-2-sulfonyl chloride illustrates a differentiating structural feature: the 6-isomer positions the reactive sulfonyl group para to the endocyclic nitrogen, whereas the 2-isomer places it adjacent to the ring junction, leading to steric shielding and a dramatically reduced coupling rate with secondary amines (less than 5% conversion after 4 hours under standard conditions). This positional specificity makes the 6-sulfonyl chloride the preferred intermediate for synthesizing elongated sulfonamide libraries where the benzothiazole core must remain unhindered at the 2-position for subsequent functionalization, such as Suzuki couplings using 2-bromo- or 2-iodobenzothiazole precursors. The 6-sulfonyl chloride’s compatibility with palladium-catalyzed cross-coupling in a one-pot sequential protocol—sulfonamide formation followed immediately by Suzuki reaction—has been demonstrated using Pd(PPh₃)₄ (2 mol%) and aqueous Na₂CO₃ in DME at 80 °C, delivering biaryl sulfonamides in 72–88% isolated yields without intermediate purification. Attempting the same sequence with the 5-sulfonyl chloride regioisomer resulted in a complex mixture due to competing palladium insertion at the activated C–Cl site, yielding less than 30% desired product.