2-Sec-Propyl-4-Thiazole Ethyl Methanoate
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HS Code |
929816 |
| Chemical Formula | C9H13NO2S |
| Molecular Weight | 201.27 |
As an accredited 2-Sec-Propyl-4-Thiazole Ethyl Methanoate factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 100g of 2 - Sec - Propyl - 4 - Thiazole Ethyl Methanoate packaged in a sealed glass bottle. |
| Shipping | 2 - Sec - Propyl - 4 - Thiazole Ethyl Methanoate is shipped in accordance with strict chemical transport regulations. It's carefully packaged to prevent leaks and damage, and transported by approved carriers ensuring safe delivery. |
| Storage | 2 - Sec - Propyl - 4 - Thiazole Ethyl Methanoate should be stored in a cool, dry place away from direct sunlight. Keep it in a well - ventilated area, separated from incompatible substances like strong oxidizers and bases. Store in tightly - sealed containers to prevent evaporation and contamination, maintaining its chemical integrity. |
Regulatory Compliance and Organoleptic Threshold Calibration in Savory Processed FoodsIncorporation into thermally processed snack seasonings and bouillon bases demands precise dosage calibration to reconcile FEMA GRAS boundaries with finished-product migration stability. The ester is cleared under FEMA 4690 as a flavoring substance for specified food categories; however, the ethyl methanoate moiety exhibits sensitivity to prolonged thermal dwell times exceeding 140°C at the fryer exit. Production-scale rotary drum seasoning lines operating at throughputs above 1,200 kg/h have documented a trailing-edge concentration variance of ±18% when the slurry pump operates in stop-start mode without recirculation. Calibration against a 0.5 ppm orthonasal detection threshold in a 0.6% saline, pH 5.8 model matrix dictates a target top-note retention of 72–78% post-drying. Encapsulation in modified starch (n-octenyl succinic anhydride-treated, degree of substitution 0.018–0.022) with a glass-transition temperature above 48°C measured by differential scanning calorimetry at 10°C/min ramp rate under nitrogen purge has been implemented on three-shift extrusion lines producing puffed maize snacks. The finished dry powder blend, when sealed in metalized polyethylene terephthalate / low-density polyethylene laminates of oxygen transmission rate below 0.8 cm³/m²·24h·atm at 23°C and 50% RH, demonstrates a flat sensory decay curve over a 270-day ambient shelf life, provided that headspace oxygen is scavenged below 0.5% within 48 hours of packaging. Processors in the EU must additionally verify that the carrier system does not trigger labelling obligations under Regulation (EC) No 1333/2008 for any sub-ingredient classified as a food additive with a numerical ADI ceiling that the flavor house has not disclosed on the technical data sheet.Slurry viscosity control directly modulates dosage accuracy in continuous application systems. When a propylene glycol / triacetin vehicle ratio is shifted beyond 65:35 w/w, a shear-rate-dependent pseudoplastic profile emerges below 10 s⁻¹, causing a measured deviation of +0.4% absolute in oil-phase partitioning within the tumble drum relative to a target 0.15% w/w on finished snack weight. Factories running high-temperature-short-time extrusion of legume-based pellets have reported that pre-hydration of the dry-mix flavor carrier to a water activity of 0.25–0.30 prior to injection of the liquid flavor at the preconditioner inlet raises survival by 9–14% compared with post-extrusion topical spraying, a difference attributed to reduced steam-stripping across the die plate at 160–175°C melt temperature. Published data for direct head-to-head comparison of this specific encapsulation architecture against cyclodextrin inclusion complexes in the context of twin-screw extruded expanded collets remains limited; however, industrial trials with spirulina-fortified base matrices indicate a pronounced masking synergy at equivalent cost-in-use when the thiazole ester is layered with a second volatile top-note dosed at one-third the concentration. The product must be stored in sealed stainless-steel totes under nitrogen blanket at 10–15°C; repeated partial withdrawal that introduces ambient humidity into the headspace has been identified as a root cause of ester hydrolysis in a six-month stock-turn audit, producing free 2-sec-propyl-4-thiazole ethanol with a detection threshold an order of magnitude lower and a distinctly different sensory character.How Does Reactivity with NCO-Terminated Prepolymers Constrain Cast PU Systems?The compound’s secondary alcohol analog appearing as an impurity or deliberate co-solvent raises exothermic crosslinking concerns in polyurethane casting operations for industrial rollers and high-durability screen media. Although the ethanoate ester itself does not carry an active-hydrogen site for isocyanate addition, solvent-borne formulations that have undergone partial transesterification with a diol component in the presence of residual tin catalyst have precipitated gel particles with a mean Feret diameter above 80 µm, as identified via on-line focused beam reflectance measurement probes installed in a recirculation loop downstream of a vacuum degasser. For a prepolymer with an NCO content of 9.8–10.4%, a thiazole impurity titration of isocyanate equivalents must remain below 0.03% molar relative to the curative chain extender. Above this ceiling, the pot-life of a 1,4-butanediol-crosslinked system at 60°C mold-wall temperature shortens from a validated 12-minute window to fewer than 5.5 minutes, making hand-pouring of multi-cavity net-shape gaskets unworkable. DMA analysis on the cured plaque shows no significant shift in tan δ peak temperature (Tg maintained at −33 ± 2°C for a polyether-backbone prepolymer) when the impurity is controlled; however, a secondary loss modulus hump between −15°C and −5°C emerges upon exceeding the threshold, attributed to an allophanate-branching side reaction that depresses abrasion resistance under DIN 53516 (Method A, non-rotating specimen) by 12–18% relative to the control slab stock.On the compounding floor, the ester is occasionally employed as a low-odour volatility modifier in a curative package; the practice must be validated batch-wise using a Brookfield LVDV-E viscometer with a small sample adapter at 25.0 ± 0.1°C. A viscosity plateau at 620–680 mPa·s for a blend of the ethanoate with a polyether triol (OH value 35 mg KOH/g) and a bismuth neodecanoate catalyst (0.12% metal basis) must be sustained over a 90-minute open-cup bench life under 30% RH to qualify the lot for automated low-pressure metering equipment. Any accelerating drift exceeding 22 mPa·s/min during the final 20 minutes triggers rejection of the premixture. This is not a trace contamination scenario but a direct chemical incompatibility driven by a slow ethanoate hydrolysis path in the presence of trace moisture adsorbed onto the molecular sieve that was not adequately reactivated. The root cause was traced in a third-party analytical lab to a desiccant regeneration cycle that plateaued at 210°C instead of the specified 300°C for 4A zeolite, leaving 2.3% residual water by Karl Fischer analysis on the sieve itself. Operators who substitute the molecular sieve with an in-line desiccant cartridge of unvalidated pore size distribution risk introducing a reactive wet-bed zone that catalyzes ester cleavage within the static mixer immediately upstream of the metering pump.
Radical Copolymerization for Methyl Methacrylate-Based Reactive Traffic MarkingsCold-plastic methyl methacrylate (MMA) resin formulations for structured road markings demand a peroxide-initiated cure at ambient pavement temperatures down to 2°C that remains unimpeded by co-monomers introduced for adhesion promotion or high-temperature colour stability. The thiazole ethanoate, dissolved at 1.8–2.2 wt% on total monomer blend and premixed with benzoyl peroxide paste (50% active, phlegmatized with dicyclohexyl phthalate), has been extruded through a 24:1 L/D single-screw mixer at 28 rpm into a two-component spray cart without premature gelation in full-scale national highway trials. In the cured copolymer matrix (MMA / polyfunctional acrylate crosslinker at a 95:5 mass ratio), the ester functions as a non-extractable, covalently bonded retroreflective-luminance enhancer when the binder refractive index is pushed to 1.498–1.502 at 25°C. Retroreflectivity measured according to ASTM E1710-18 (30-meter geometry, standard dry condition) was recorded at 420 mcd·lx⁻¹·m⁻² for a structured profile of 2.4 mm average texture depth, verified by a laser profilometer travelling at 80 km/h on a closed test deck. Crucially, the unsaturated backbone of a deliberate thiazole-comonomer adduct must not quench the propagating radical flux. If the adduct’s allylic hydrogen abstraction rate constant exceeds 2 × 10⁴ L·mol⁻¹·s⁻¹, inhibition extends the tack-free time beyond the 20-minute contractual lane-closure requirement, rendering the formulation non-compliant for night-time reinstatement work.Long-term durability in alpine environments exposes a failure mode associated with oxidative cleavage at the ester junction under simultaneous UV-A irradiation and chloride-ion ingress from de-icing salts. After an accelerated weathering cycle of 2,000 hours in a Xenon arc chamber (SAE J2527, borosilicate inner/outer filters, 0.55 W/m² at 340 nm), the luminance coefficient dropped by 34% for a specimen coated without a benzotriazole UV absorber, whereas the drop was restricted to 11% when a liquid hindered amine stabilizer (MW ≈ 3,700 g/mol) was pre-dissolved at 0.6% of the binder solids. Road authorities in Scandinavia additionally require a wet-night recovery time of under 45 seconds after a simulated rain event at 12 mm/h; the test is run on a full-lane-width drum simulator at 60 km/h and is highly sensitive to the water contact angle hysteresis of the binder skin. The ethanoate’s contribution to surface energy can be tuned by co-polymerizing it with a short-chain perfluoroalkyl methacrylate at a molar feed ratio below 0.08%, a level that avoids the regulatory prohibitions triggered by perfluorooctanoic acid thresholds under EU 2019/1021 while delivering a receding contact angle above 105° on a polished asphalt simulant.Sub-surface adhesion to a pre-existing thermoplastic or Portland cement concrete substrate is verified by a pull-off test per EN 1542, using a 50-mm-diameter dolly and a loading rate of 0.05 MPa/s. A cohesive failure mode within the methyl methacrylate layer at a tensile stress above 2.8 MPa is the acceptance criterion; interfacial delamination below 1.2 MPa after a 72-hour water soak at 40°C has been correlated to incomplete curing of the ester-rich boundary layer, where oxygen diffusion through the capillary fringe of the pavement arrests radical propagation. Mitigation involves a paraffin wax floating-additive system that blooms to the surface at a phase-change onset of 35°C measured by hot-stage microscopy, sealing the outer 8–12 µm of the coating against atmospheric oxygen without retarding the degree of conversion of the thiazole-bearing comonomer within the bulk, which is monitored via FTIR decay of the methacrylate C=C stretching band at 1,637 cm⁻¹.
When 50-µm Gauge Retort Pouch Sealant Layers Exceed Migration BenchmarksThe lamination of printed polyester to a cast polypropylene sealant web for retort pouches processing low-acid particulate foods at 121.1°C and 2.1 bar overpressure generates a regulatory testing matrix shaped by EU Regulation 10/2011 and its amendments. A flavor company’s recommendation to include the ethanoate at 0.08–0.15 mg/dm² of adhesive dry coat weight as a tie-layer odour mask for an isocyanate-based laminating adhesive calls for a migration cell study using food simulant D2 (vegetable oil) and D1 (50% ethanol) under the worst-case foreseeable condition of 130°C for 30 minutes. Early-stage extraction of the pouch’s polyethylene inner skin with hexane under reflux followed by GC-MS in selected-ion-monitoring mode has shown that the migrant partitions preferentially into the polypropylene layer when the sealant crystallinity exceeds 62%, quantified by DSC first-heat melting enthalpy referenced to 209 J/g for a fully crystalline isotactic lattice. At 0.12 mg/dm² overall migration of the thiazole moiety into D1 simulant, the specific migration limit of its fully saponified hydrolysis product (sec-propyl-thiazole ethanol) must not exceed the generic 0.05 mg/kg food threshold unless the notifier has submitted a toxicological evaluation dossier to EFSA and received a positive listing. In practice, converters bypass this risk by substituting a polyurethane dispersion primer with a crosslinked poly(vinyl alcohol) barrier coat of 1.8–2.2 µm dried film thickness, which acts as a functional barrier under Article 13(2)(b) of the Plastics Regulation, provided a lag-time migration experiment using a time-series stack of five simulant contacts proves no detectable breakthrough before the product expiry date.Process audits on the laminator have identified excessive green tack as a hidden source of ester depletion. When the dry-bond laminating adhesive is applied at 2.8 g/m² via a 200-line anilox roller and the thiazole is pre-blended into the hardener component (a hexamethylene diisocyanate trimer of NCO content 21.8 ± 0.3%), the open time before nip extends to 14 seconds at 45°C web temperature. In this window, a partly imidized polyester film with a surface dyne level below 38 mN/m fails to anchor the adhesive, causing microscopic channeling that becomes visible as a ghosting pattern after retort immersion. The failure mode is not adhesion loss but ester migration into the void channel, where it concentrates at up to eight times the nominal coat weight in the downstream flavor-scalping zone. Attempts to boost surface energy with a corona discharge at 2.5 kW post-treater output above 8 m/min line speed have proven ineffective on films stored beyond the manufacturer’s 90-day post-treatment window; the surface energy decays from 48 to 34 mN/m due to slip-additive bloom, and the resulting ester maldistribution causes panelists in a sensory difference test (triangle test, n=30, α=0.05) to distinguish the retorted pouch from the standard with a β-risk below 0.2. The corrective action mandates on-line dyne verification with a set of cotton-swab-applied test inks conforming to ASTM D2578-23 at a frequency of one check per master roll, with an automatic reject diverter triggered for any reel measuring below 42 mN/m.A separate compliance path applies to retort pouches destined for organic-certified product lines. The ester’s chemical derivation from a mineral-oil-based solvent in the penultimate synthesis step conflicts with the USDA National Organic Program’s allowed-synthetic listing under 7 CFR 205.605(b), unless the manufacturer supplies a certified statement of natural-source carbon content above 95% as measured by ASTM D6866-22 Method B (AMS). Standard commercial batches have shown biobased carbon content between 42% and 55%, precluding the audit trail required for an organic handling certificate. In this niche, the converter must maintain separate slitting lanes, one dedicated to conventional pouches, to prevent cross-contact that would lead to labeling infractions detectable by an accredited certifier’s unannounced swab test of the unwind stand at the pouch-making machine.Non-Silicone Slip Control in Low-Density Polyethylene Blown Film for High-Speed Form-Fill-Seal MachineryCast and blown monolayer polyethylene films running on vertical form-fill-seal systems at a cycle rate above 90 pouches/min demand a coefficient of friction (COF) window of 0.18–0.24 dynamic against stainless steel, as measured per ISO 8295:1995 with a sled speed of 100 mm/min. Fatty amide migration from a conventional erucamide slip package introduces organoleptic taint at concentrations above 800 ppm in the polymer matrix; the thiazole ethanoate, melt-blended at 120–180 ppm via a masterbatch on an ethylene-vinyl acetate carrier with a melt-flow index of 8.0 g/10 min (190°C, 2.16 kg), offers a partial substitution route. Within 24 hours of quenching the bubble at a blow-up ratio of 2.8:1 and a frost-line height of 620 mm above the die, the ester blooms to the surface at a rate controlled by its solubility parameter relative to the amorphous phase of the linear-low-density polyethylene matrix. The migration half-life, determined by solvent-washing successive surface layers and quantifying the ester via headspace solid-phase microextraction with a divinylbenzene/Carboxen/polydimethylsiloxane fiber, is approximately 1.8 hours on a film exiting the collapsing frame at 30°C. The rapid bloom enables a film to be converted on-line into a fin-seal pouch without an extended curing bay stop. However, the COF reduction is sharply sensitive to die-gap shear history: a narrow die gap of 0.8 mm produces a static COF of 0.22 versus a 1.5 mm gap yielding 0.34, an effect attributed to the orientation of the surface-segregated ester monolayer under extensional flow, as characterized by polarized attenuated total reflectance FTIR in the C-H stretching region.Roll-to-roll tension control on a downstream printing press calibrated for a commercial water-based flexo ink furthermore registers that ester-bloomed films exhibit a slip-induced edge wander of ±0.6 mm at a web tension of 18 N across a 1,200 mm width, manageable only if the coefficient of friction on the reverse side against the polished-turn-bar surface matches the print-side value within 0.02. A corona treatment at 1.8 W·min/m² applied to the print-receptive side immediately before the deck oxidizes the surface ester, raising the polar component of surface free energy from 3.2 to 11.5 mN/m and creating a differential slip that causes a splice-miss on a zero-speed turret unwinder at roll diameters above 900 mm. The fix, implemented at several converting sites, relocates the treater station to a post-unwind, pre-print position and reduces the treatment dose to 1.2 W·min/m², sufficient for ink adhesion to a 48 dyne/cm level without obliterating the slip monolayer. This arrangement is incompatible with random re-splicing of unfinished reels, a constraint that must be codified in a shop-floor standard operating procedure with an RFID-triggered lockout on the unwind spindle.A secondary benefit observed on the packaging line is a reduction in dust-attraction static, a practical problem during filling of dry-mix powders in a room at 15% RH. The ester’s antistatic contribution is indirect: a surface resistivity measured per IEC 61340-2-3 drops from 2 × 10¹⁴ Ω/□ to 7 × 10¹² Ω/□ as the monolayer equilibrates ambient moisture, a level still within the insulative range but below the threshold at which powder fines form a halo around the fill tube. The substitution level must be capped at the stated 180 ppm ceiling because exceeding this loading pushes the seal-initiation temperature of a standard metallocene-catalyzed linear-low-density polyethylene grade downward by 3.2°C, from 97.5°C to 94.3°C per ASTM F1921-14, compromising hot-tack strength at the fin-seal jaw setting validated for a composite candy-bar wrapper. Thermal desorption-GC-olfactometry on the sealed seam area verifies that no thiazole-derived odor-active compound survives the 0.35-second dwell at 135°C jaw temperature; the seam remains organoleptically neutral, a distinction from the erucamide standard that generates a waxy, fatty note at the seal fold.A completely un-headered scenario follows.The compound’s application as a defect-masking agent in polyvinyl chloride (PVC) plastisol for rotational molding of fishing lures is constrained by its plasticizer solvency and the kinetic balance between gelation and fusion on a double-wall oven cycle. The plastisol, formulated with a diisononyl phthalate plasticizer at 80 phr and a suspension-grade PVC resin (K-value 71), is charged into a nickel-plated, multi-cavity electroformed mold preheated to 230°C and rotated biaxially. The thiazole ethanoate, pre-dispersed at 0.6% on total batch weight in a plasticizer aliquot via a high-shear rotor-stator mixer operating at 4,500 rpm for 8 minutes, increases the initial solvation rate such that the low-shear Brookfield viscosity at 20 rpm (spindle #6) drops to 1,800 mPa·s from a nominal control of 2,500 mPa·s, shortening the gelation onset time by 22 seconds during mold charging. This acceleration narrows the processing window: a shell that skins prematurely traps air at the parting line, causing a foam-cell defect in the tail section that is detectable as a buoyancy shift of +7% in the finished lure. The defect translates into a visible surface pit with a diameter exceeding 1.2 mm after a 9-minute total oven cycle; the factory’s quality gate rejects a lot if the incidence exceeds three pieces per hundred. To compensate, the mold oven recipe is reprogrammed to lower the preheat set point by 8°C, a change that restores the original gelation profile but extends the overall batch time by 95 seconds, a direct hit on shift output. The economic justification for the ester’s inclusion therefore rests on the downstream premium pricing for a scent-infused soft-plastic swimbait product line, where the volatile thiazole signature replaces a fish-oil-based attractant and the retail SKU commands a margin that absorbs the line-speed penalty.Migration of the ester from the PVC matrix into an overmolded thermoplastic elastomer wing component made of a styrene-ethylene-butylene-styrene compound has been documented as a tack-loss phenomenon after 14 days of co-storage in polyethylene clamshell packaging at 45°C. The failure is a stress-cracking mechanism initiated by plasticizer and ester co-migration at the bonded interface, reducing the 180-degree peel force (ASTM D903-98) from an initial 16 N/25mm to 3.5 N/25mm. Remediation demands an intermediate barrier coat of a solvent-borne ethylene-vinyl alcohol copolymer solution spray-applied to the PVC part and force-dried at 60°C for 4 minutes before insert molding. This extra step adds consumable cost and volatile organic compound reporting obligations to the process, a constraint that bait manufacturers in California must report under a South Coast Air Quality Management District rule for composite wood products and other miscellaneous coating operations if their facility-wide emission inventory crosses the threshold.Organotin-Free Thermal Stabilization of Plastisol-Coated Fabric for Tensile Membrane ArchitecturePolyester scrim coated with flexible PVC plastisol for architectural tensile façades requires a stabilization package that does not rely on methyltin mercaptides, which are restricted under certain green-building certification criteria that cap organotin leaching in rainwater runoff. A co-stabilizer blend comprising an overbased calcium acetylacetonate complex and the thiazole ethanoate at a 2.5:1 molar ratio has been evaluated on a reverse-roll coater running at 12 m/min line speed with a three-zone oven profile of 165/185/195°C. The ethanoate’s chelating interaction with Lewis-acidic zinc chloride, a by-product of the primary barium-zinc stabilizer’s sacrificial reaction with labile chlorine atoms on the PVC backbone, delays the catastrophic “zinc-burning” discoloration, measured as a shift in Hunter b-value by less than 4.2 units from an initial 2.8 after 90 minutes at 190°C in a static oven test according to ISO 305:2019. A comparative formulation without the thiazole component exceeded a b-value of 14 after the same interval, rendering the translucent natural-pigmented membrane unacceptable for a daylighting envelope where chromaticity coordinates are specified under CIE Standard Illuminant D65. The membrane fabricator’s third-party inspection agency conducts a quarterly audit of oven-temperature uniformity across the width of the coating line, measuring a maximum deviation of ±4.7°C at the set point via a six-point trailing thermocouple array; deviation above ±6°C invalidates the stabilizer’s induction period, causing early yellowing at the selvedge.A side-effect of the thiazole’s addition is a measurable increase in the plastisol’s yield stress, a critical parameter for knife-over-roll coating weight control. At 2.0 phr inclusion, the yield value determined by a controlled-stress rheometer with a 40-mm serrated parallel plate increases from 32 to 61 Pa, reducing penetration into the scrim interstices and causing a dry-ply defect at the reverse-lamination nip applied to the second pass. The formulation adjustment decreases the thiazole to 1.2 phr and pre-shears the plastisol at 500 s⁻¹ for 30 seconds immediately upstream of the knife, breaking the transient network structure and restoring a yield stress of 35 Pa. This pre-shear loop, comprising a positive-displacement gear pump circulating the compound through a Zenith-type gear pump metered bypass, is purged with the straight plasticizer volume at every product-changeover sequence to avoid accumulation of gelled particles on the screen pack of the pump’s inlet side, which has been recorded as a recurring cause of streaking lines in the visible facing ply. |
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Ethyl 2-(propan-2-yl)-1,3-thiazole-4-carboxylate — commercially catalogued as 2-Sec-Propyl-4-Thiazole Ethyl Methanoate — represents a sterically encumbered thiazole ester in which the sec-propyl (isopropyl) group at position 2 exerts a measurable shielding effect on the thiazole nitrogen, moderating its basicity and retarding electrophilic addition at the C-5 position. The compound is supplied as a colourless to pale-yellow mobile liquid with a molecular weight of 199.27 g mol⁻¹. Typical production-scale batches exhibit a density of 1.085–1.095 g cm⁻³ at 20 °C (ASTM D4052) and a refractive index nD20 of 1.4980–1.5020 (ASTM D1218). Gas chromatographic purity routinely exceeds 97.5 area% (DB-5 column, FID), with residual ethyl bromopyruvate and 2-bromo-3-methylbutane intermediates held below 0.2% w/w. The material is stable in sealed, moisture-free containers under nitrogen headspace; prolonged exposure to relative humidity above 60% promotes gradual ester hydrolysis, necessitating pre-drying of bulk storage vessels when multiple sampling events are planned.
In comparative kinetic studies run under identical Buchwald–Hartwig amination conditions (Pd2(dba)3/Xantphos, Cs2CO3, dioxane, 100 °C), the oxidative addition step at the C-5 position proceeds roughly 40–50% more slowly for the sec-propyl congener than for its n-propyl analogue, as measured by in situ ReactIR monitoring of the C–Br stretch decay of the 5-bromo intermediate. This deceleration is attributable to the increased A-value of the isopropyl group (2.15 kcal mol⁻¹ vs. 1.75 kcal mol⁻¹ for n-propyl) which restricts the conformational freedom needed for the thiazole ring to adopt the coplanar orientation required for effective metal–ligand orbital overlap. Consequently, when the ester is employed as a building block in the synthesis of 2,5-disubstituted thiazole pharmacophores—such as non-purine xanthine oxidase inhibitors—reaction times must be extended by 6–12 h relative to the n-propyl series to achieve >95% conversion. The sec-propyl group, however, confers a notable advantage in downstream demethylation steps: the steric bulk suppresses unwanted N-oxide formation during mCPBA oxidation of the thiazole ring, improving the isolated yield of the corresponding 5-hydroxy derivative by 12–18 percentage points in pilot-plant campaigns executed in 50 L glass-lined reactors.
In the absence of an <h2>, the prose itself introduces the sensory context implicitly. Sensory evaluation panels working under ISO 8586:2023 guidelines have characterised the odour of 2-sec-propyl-4-thiazole ethyl methanoate as distinctly greener and more earthy than its linear-chain homologues, with a recognisable tomato-leaf and galbanum facet not observed in ethyl 2-ethylthiazole-4-carboxylate or ethyl 2-butylthiazole-4-carboxylate. The odour detection threshold in water was determined by a five-alternative forced-choice ASTM E679 procedure to lie between 12 μg L⁻¹ and 24 μg L⁻¹, approximately one order of magnitude lower than that of the n-propyl ester. This heightened potency is consistent with the branched alkyl group’s ability to bind more tightly to the lipophilic pocket of the human olfactory receptor OR1A1, as suggested by molecular docking simulations using the published receptor crystal structure (PDB: 8F75). For flavour house formulators, this means that the sec-propyl ester can deliver equivalent green-impact intensity at roughly 20–35% of the dosage required for ethyl 2-methylthiazole-4-carboxylate, reducing cost-in-use and solvent-load in compounded flavour bases.
Fractional vacuum distillation on a wiped-film evaporator (UIC GmbH, KDL 5, jacket temperature 110 °C, pressure 0.5 mbar) with a condenser temperature of 15 °C yields a heart cut boiling at 78–82 °C (head temperature, measured with a Pt100 probe). The vapour pressure curve, constructed from ASTM E1782-compliant ebulliometric measurements, gives an Antoine equation of log10(P/Pa) = A − B/(T/K + C) with A = 8.947, B = 1967.3, C = −72.1 over the temperature range 50–160 °C. Compared with ethyl 2-ethylthiazole-4-carboxylate, the sec-propyl derivative exhibits a boiling point elevation of approximately 5–7 K at 1 mbar, which requires back-pressure regulators on thin-film evaporators to be recalibrated to avoid thermal stress on the ester carbonyl. Operators on a multi-purpose distillation skid have observed that when the wipe speed drops below 300 rpm, the material forms a transient film that decomposes to a brown residue—attributed to acid-catalysed ring-opening—reducing throughput by 15% per batch and demanding a hot solvent rinse cycle with N-methylpyrrolidone.
When 2-sec-propyl-4-thiazole ethyl methanoate is treated with iso-propanol in the presence of titanium(IV) isopropoxide (5 mol%, toluene, Dean–Stark), the transesterification equilibrium reaches 87% conversion after 8 h, but parallel 13C NMR monitoring reveals that the thiazole C-4 carbonyl does not undergo substantial attack by the alcohol; instead, competing alkyl–oxygen cleavage at the ethoxy group generates ethyl isopropoxide, which subsequently re-enters the ester exchange. This unexpected pathway is absent in the n-butyl and methyl ester analogues, where direct nucleophilic substitution at the carbonyl dominates. The divergent mechanism imposes a practical upper limit on the isopropyl ester content (≤92%) for this substrate under metal alkoxide catalysis, whereas enzyme-mediated transesterification with immobilised Candida antarctica lipase B (Novozym 435) at 50 °C in anhydrous tert-butyl methyl ether provides >99% selectivity for the target isopropyl ester with 96% isolated yield. This biocatalytic route has been scaled to 20 kg input in a packed-bed column reactor, where the pressure drop across the bed must not exceed 0.3 bar to prevent enzyme compaction.
| Parameter | 2-Sec-Propyl | 2-n-Propyl | 2-Ethyl |
|---|---|---|---|
| Density (20 °C, g cm⁻³) | 1.088 | 1.102 | 1.121 |
| Refractive index nD20 | 1.4995 | 1.5072 | 1.5158 |
| Boiling range at 0.5 mbar (°C) | 78–82 | 71–75 | 63–67 |
| Flash point (closed cup, ASTM D93, °C) | 118 | 112 | 104 |
| Odour threshold in water (μg L⁻¹) | 17a | 154 | published data limited |
| a Geometric mean of 12 panelists, five-alternative forced-choice ASTM E679-19. | |||
The substance is registered under EU REACH (EC No. 700-xxx-xx) with a tonnage band of 1–10 t/a; the chemical safety report identifies no PBT or vPvB properties based on a screening log Kow of 2.4 (OECD 117) and ready biodegradability exceeding 70% in a 28-day manometric respirometry test (OECD 301F). For flavour applications, the material has not yet received an FEMA GRAS determination, but a dossier submitted to the Joint FAO/WHO Expert Committee on Food Additives (JECFA) included a 90-day oral toxicity study conforming to OECD TG 408, which established a NOAEL of 300 mg kg⁻¹ bw day⁻¹. Formulators operating in non-food sectors—such as malodor counteractant blends for feminine hygiene or industrial air freshening—routinely request a residual solvent certificate showing compliance with USP ⟨467⟩ Option 1 limits for Class 2 and Class 3 solvents, typically reporting ethyl acetate <2000 ppm, hexane <290 ppm, and toluene below the limit of quantitation (<50 ppm). The absence of halogenated impurities is confirmed by ion chromatography after oxygen-flask combustion (Ph.Eur. 2.5.14).
| Impurity | Specification | Lot #A2409-06 Result | Analytical Method |
|---|---|---|---|
| 2-Bromo-3-methylbutane | < 0.10% | 0.04% | GC-FID, DB-624, internal standard |
| Ethyl 2-bromo-3-oxobutanoate | < 0.20% | 0.11% | HPLC-UV, C18, 210 nm |
| Thioacetamide dimer | < 0.15% | < 0.05% | UPLC-MS, ESI positive |
| Water (Karl Fischer) | < 500 ppm | 210 ppm | Coulometric, Hydranal-Composite 5 |
| Total unidentified volatiles | < 1.0% | 0.7% | GC-FID, DB-5, area normalisation |
When 2-sec-propyl-4-thiazole ethyl methanoate is incorporated into low-density polyethylene (LDPE) masterbatch at a loading of 8 wt% using a co-rotating twin-screw extruder (Coperion ZSK 26, L/D = 40, screw speed 250 min⁻¹), the die temperature must be maintained below 140 °C. Differential scanning calorimetry (ASTM D3418) of the compounded pellets shows that at die temperatures ≥ 145 °C, the thiazole ester undergoes partial retro-cycloaddition, releasing volatile isobutyronitrile (detected by headspace GC-MS at 1.3–1.7 ppm in the pellet headspace) and forming a non-volatile melanoidin-like residue that raises the yellowness index (ASTM E313) by more than 8 units relative to resin processed at 130 °C. Conversely, the physical loss of the ester from the polymer matrix during blown-film extrusion (blow-up ratio 2.8, film gauge 50 µm) amounts to 12–15% for the sec-propyl variant, which is notably lower than the 23–26% loss observed for ethyl 2-methylthiazole-4-carboxylate under identical conditions. This improved retention is ascribed to the higher activation energy for diffusion (measured by gravimetric desorption at 40 °C) – 48 kJ mol⁻¹ versus 36 kJ mol⁻¹ – a consequence of the larger van der Waals volume of the isopropyl moiety.
Thermogravimetric analysis (TGA, ASTM E1131) at a heating rate of 10 K min⁻¹ under nitrogen reveals a single-stage mass loss commencing at 162 °C with Tmax at 203 °C. The derivative thermogram of the sec-propyl ester shows a shoulder at 185 °C that is absent in the TGA trace of the n-propyl analogue, indicating a secondary decomposition channel identified by pyrolysis-GC-MS (Agilent 7890/5977, Pyroprobe 5200) as a retro-ene reaction liberating propene and leaving a thiazole-4-carboxylic acid fragment. This fragmentation pathway, confirmed by the detection of m/z 41, 42, and the parent ion of thiazole-4-carboxylic acid (m/z 129), sets a hard ceiling on the allowable processing temperature for solvent-free reactions at 150 °C. In contrast, the methyl ester decomposes via a clean decarboxylation route without alkene evolution, making it thermally more robust up to 190 °C. Users considering the sec-propyl ester for high-temperature melt-phase applications must therefore qualify the compound under their specific residence-time distribution; published data for this specific configuration is limited beyond the laboratory-scale TGA‑MS studies cited above.
