2-Mercapto-5-Methyl-1,3,4-Thiazole

In accelerated sulfur vulcanisation of natural rubber, partial replacement of mercaptobenzothiazole (MBT) with 2-mercapto-5-methyl-1,3,4-thiazole at a substitution ratio of 30–50 mol% modifies the scorch delay and crosslink density profile. Kneaded on a two-roll mill with a friction ratio of 1:1.25 and a front roll temperature maintained at 60 ±3 °C, the compound exhibits a lower torque onset in an MDR rheometer per ASTM D5289-17 at 150 °C: minimum torque M_L drops by approximately 8–12 % compared to the MBT reference, while t_s2 shortens by 20–35 seconds without altering the 90 % cure time t₉₀ beyond 0.5 minutes. This behaviour is attributed to the electron-donating methyl group increasing the nucleophilicity of the thiolate anion, which accelerates the formation of zinc–accelerator complexes in the presence of 5 phr zinc oxide and 2 phr stearic acid. Typical compounding for a tyre tread base formulation involves 100 phr natural rubber, 50 phr N330 carbon black, 5 phr ZnO, 2 phr stearic acid, 1.5 phr sulphur, 0.8 phr of the thiazole, and 0.15 phr tetramethylthiuram disulfide (TMTD). The accelerator is pre-dispersed in a binder at 75 % active content and added at the final stage of mixing to avoid frictional heat history above 85 °C. Post-vulcanisation tensile strength measured per ISO 37:2017 at 500 mm/min shows an increase of 1.5–2.1 MPa in the modulus at 300 % elongation, while tear strength per ISO 34-1, Method B improves by 6–9 N/mm. The final articles cover conveyor belt covers and vibration damping mounts. A critical processing window exists: the compound must be cooled to below 35 °C within 20 minutes after milling to prevent bin scorch. Co-agents such as sulphenamide accelerators (CBS or TBBS) at doses above 0.3 phr induce a hyper-reticulation risk, evidenced by a rapid torque increase exceeding 12 dNm in the MDR plateau. Storage stability requires sealed, moisture-proof packaging at ≤30 °C and ≤65 % RH; exposure to humidity above 70 % for 72 hours leads to hygroscopic caking and loss of active thiol titer by 0.8 % as determined via iodometric titration.

What Limits Copper Leaching Rates in Water-Miscible Metalworking Fluids?

A water-dilutable metalworking fluid concentrate formulated with 12 % tall oil fatty acid, 6 % triethanolamine, 4 % petroleum sulfonate, and 0.08–0.15 wt% of 2-mercapto-5-methyl-1,3,4-thiazole demonstrates effective yellow metal passivation when diluted to 5 % v/v in water of 200 ppm hardness as CaCO₃. Copper strip corrosion tests conducted per ASTM D130 at 60 °C for 4 hours consistently achieve a rating of 1A, whereas a benzotriazole (BTA)-based reference at equimolar active concentration drops to 2C within the same period once the fluid accumulates 1500 ppm chloride contamination. The thiazole’s resistance to precipitation in the presence of calcium and magnesium ions is linked to its heterocyclic structure, which sterically hinders the formation of insoluble metal–thiolate aggregates. Field monitoring via direct titration with 0.01 N iodine solution maintained a free thiol level of 0.9–1.2 μeq/mL over 6 months of sump life in a transfer line machining brass C36000 parts, while BTA levels required replenishment every 14–18 operating days. The concentrate is manufactured by heating the fatty acid and amine to 80 °C under nitrogen, then charging the thiazole at 65 °C with high-shear dispersion at 1500 rpm for 25 minutes. Incompatibility with chlorine-releasing biocides and bromine-based oxidizers is absolute: residual free chlorine as low as 0.5 ppm oxidises the thiol to the disulfide within 90 minutes, eliminating both corrosion protection and biocidal contribution. Formulations destined for aerospace alloy machining (aluminium 7075, magnesium AZ31) must additionally incorporate 0.02 % diethylenetriaminepenta(methylenephosphonic acid) to chelate cationic aluminium residues that otherwise catalyse thiol oxidation under shear. The finished metalworking fluid complies with the EU Ecolabel Decision (EU) 2017/1218 and is REACH-registered under a joint submission. End-use products: semi-synthetic coolants for precision grinding and broaching of copper alloy components, including heat exchanger plates and valve bodies.

Galvanostatic measurements in acid copper sulphate baths containing 75 g/L CuSO₄·5H₂O, 190 g/L H₂SO₄ and 60 mg/L chloride ions reveal that addition of 3–5 mg/L 2-mercapto-5-methyl-1,3,4-thiazole shifts the cathode polarisation curve by 30–45 mV more negative at 2 A/dm² compared to a bath containing only bis-(sodium sulfopropyl)-disulfide (SPS) and polyethylene glycol. A Hull cell evaluation using a 267 mL cell operated at 2 A for 5 minutes at 25 °C with continuous air agitation produces a bright deposit range extending from 0.4 A/dm² to 8.5 A/dm², with semi-bright transition occurring only beyond the high-current-density edge. The thiol serves as a leveler and grain refiner, suppressing columnar growth and reducing the average crystallite size from 68 nm to 42 nm as determined by X-ray diffraction line broadening of the (111) reflection. Cross-section examination of plated through-holes on 1.6 mm thick FR-4 substrates after 60 minutes plating at 2 A/dm² yields a throwing power of 92 % measured by the ratio of minimum to maximum copper thickness per IPC-6012 Class 3 requirements. Bath life stability demands stringent carbon treatment whenever the concentration of the thiol’s degradation product, identified by HPLC at retention time 4.8 minutes, exceeds 12 mg/L; otherwise, the macro-throwing power deteriorates by 1.5 % per 100 A·h/L. Organic contaminant monitoring is performed by cyclic voltammetric stripping (CVS) with a platinum rotating disc electrode at 2500 rpm, using a dilution factor that maintains the suppression signal between 0.7–0.9. Production lines electroplating printed circuit boards with aspect ratios up to 10:1 incorporate the additive via a dosing pump synchronized with the rectifier Amp-hour counter, maintaining the active compound at 4.5 ±0.8 mg/L. The dry film composition of the final deposit meets the bend-test ductility criteria of ASTM B489, and the electrical resistivity of the plated copper is 1.72 μΩ·cm after annealing at 120 °C for 2 hours. Equipment: insoluble titanium anodes with iridium oxide coating and a waveform pulse rectifier capable of 10 ms pulse widths are preferred to avoid anodic oxidation of the thiol at the cathode film interface.

Biofilm Under-deposit Corrosion in Open Recirculating Cooling Loops

Cooling towers operating above 4 cycles of concentration and receiving makeup water with total hardness exceeding 300 mg/L as CaCO₃ frequently experience microbially influenced corrosion (MIC) beneath biofilms containing sulfate-reducing bacteria. Intermittent slug dosing of 2-mercapto-5-methyl-1,3,4-thiazole at 25–40 ppm active (as product) every 72 hours, combined with continuous feed of 1.5 ppm free chlorine residual via a gas chlorinator, reduces sessile bacterial counts on mild steel coupons from 10⁵ CFU/cm² to below 10² CFU/cm² within 8 days, measured by the serial dilution method of ASTM E1326. In white-water loops of recycled paperboard mills, a maintenance dose of 80–150 ppm is applied at the machine chest to control slime and eliminate hydrogen sulfide odours; microbial ATP levels drop by 2 log units within 6 hours as per luciferin-luciferase assay. The chemical must not be fed upstream of chlorine dioxide injection points, because ClO₂ concentrations exceeding 0.3 ppm cleave the thiazole ring within 40 minutes, generating sulfate ions and methyl mercaptan off-gas. Monitoring of airborne methyl mercaptan at the dosing station is conducted via colorimetric tubes with a detection limit of 0.5 ppm. The product is classified as a PT12 biocide under EU BPR Regulation (EU) No 528/2012 and is authorised for use in cooling water systems with a circulation rate up to 50,000 m³/h. Compatibility with phosphonate-based scale inhibitors is verified by the absence of precipitate after 24-hour static storage at 50 °C at a 1:10 mixing ratio. End-use sectors: power generation, chemical processing, and fibreboard manufacturing, where simultaneous microbial control and copper alloy protection in condensers and heat exchangers are required.

When This Heterocyclic Thiol Is Used as a Cephalosporin Intermediate

The condensation of 2-mercapto-5-methyl-1,3,4-thiazole as a thiol nucleophile with a reactive chloroacetyl or mesyloxyimino side chain in anhydrous acetonitrile at −5 to 0 °C under a nitrogen blanket provides a thioether-linked precursor for later acylation of the 7-aminocephalosporanic acid nucleus. Potassium carbonate (1.2 eq) or triethylamine (1.1 eq) serves as the acid scavenger; excessive base concentration above 1.5 eq promotes disulfide formation, reducing the isolated yield by 8–12 %. The reaction is monitored by TLC (silica gel 60 F₂₅₄, ethyl acetate/hexane 1:2, R_f = 0.42 for the product). After aqueous workup and crystallization from isopropanol/water (7:3), the intermediate is dried under vacuum at 40 °C ±2 °C to a loss-on-drying below 0.5 %. Purity analysis by HPLC using a C18 column and acetonitrile/phosphate buffer (pH 3.0) mobile phase requires a minimum of 99.0 area-%, with the dimeric disulfide impurity controlled below 0.5 %. This intermediate is subsequently activated with thionyl chloride or reacted directly in a mixed anhydride acylation sequence to construct cephalosporin derivatives, including those with C-3 vinyl or heterocyclic thiomethyl substituents. Published synthetic details for proprietary drug candidates are limited; however, patent literature consistently references the methyl-substituted thiadiazole ring for improving pharmacokinetic profiles. The manufacturing process adheres to ICH Q7 Good Manufacturing Practice for active pharmaceutical ingredients, and residual solvent levels comply with Ph. Eur. 2.4.24: acetonitrile ≤ 410 ppm, isopropanol ≤ 5000 ppm. Packaging in 25 kg polyethylene-lined fibre drums stored at 15–25 °C under inert atmosphere ensures shelf life of 18 months. Incompatibilities include contact with strong oxidizers and high-humidity environments that trigger hydrolysis of the thioacetamide linkage back to the free thiol, depending on the particular cephalosporin scaffold.