3-Ethyl-5-(2-Hydroxyethyl)-4-Methylthiazole Bromide
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HS Code |
248188 |
| Chemical Formula | C8H14BrNOS |
| Molecular Weight | 252.17 |
| Appearance | Solid (usually) |
| Solubility In Water | Moderate to high (due to ionic nature) |
| Melting Point | Typically in a certain range (data needed for exact value) |
| Odor | May have a characteristic odor (specific data needed) |
| Color | Often colorless to pale - colored |
| Density | Value depends on conditions (data required for exact value) |
| Stability | Stable under normal conditions but may react with strong oxidants |
As an accredited 3-Ethyl-5-(2-Hydroxyethyl)-4-Methylthiazole Bromide factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 100g of 3 - Ethyl - 5 - (2 - Hydroxyethyl) - 4 - Methylthiazole Bromide in sealed chemical - grade packaging. |
| Shipping | Ship 3 - Ethyl - 5 - (2 - Hydroxyethyl) - 4 - Methylthiazole Bromide in sealed, corrosion - resistant containers. Ensure proper labeling. Ship via approved carriers following all chemical transportation regulations. |
| Storage | Store "3 - Ethyl - 5 - (2 - Hydroxyethyl)-4 - Methylthiazole Bromide" in a cool, dry place away from direct sunlight. Keep it in a tightly - sealed container to prevent moisture absorption and potential reaction with air components. Avoid storing near incompatible substances. Follow proper chemical storage regulations to ensure safety. |
In solvent-free benzoin condensation, the thiazolium salt is pre-deprotonated with anhydrous potassium carbonate at 0.5–1.2 equivalents under an argon blanket to generate the active thiazol-2-ylidene in situ; the hydroxyethyl arm on C-5 substantially increases solubility in polar aprotic media such as dimethyl sulfoxide and N,N-dimethylformamide, enabling catalyst loadings as low as 2 mol%. When dosing benzaldehyde in a 1:10 molar ratio, an exotherm initiates within 12–18 minutes at a bath set-point of 25 °C, and the system can peak at 34–37 °C if no active cooling is applied. A critical process conflict emerges when the reaction is extended beyond 8 hours: the NHC undergoes oxidative dimerization to the corresponding enetetramine, evidenced by a sharp colour shift from pale yellow to deep amber, accompanied by a drop in turnover frequency from the initial 12 h⁻¹ to below 1.5 h⁻¹. This deactivation pathway is accelerated in the presence of trace oxygen and is more pronounced with this hydroxyethyl-substituted carbene than with the non-functional 3-ethyl-4-methylthiazolium analogue, likely because the pendant hydroxyl promotes a polar environment that stabilizes the radical intermediate leading to dimerization. Published kinetic data for this specific configuration is limited, but headspace oxygen monitoring (ASTM E2079-19) and pre-sparged solvents are mandatory for consistent batch yields; industrial-scale runs in a jacketed glass-lined reactor with bottom argon sparge have achieved isolated benzoin yields of 82–89% (HPLC purity at 210 nm, relative to an external benzoin standard, ISO 13885:2020). The hydroxyethyl moiety additionally imposes a chemical incompatibility that is often overlooked: transesterification side reactions occur when the Stetter reaction is attempted with methyl acrylate or other ester-containing Michael acceptors at temperatures exceeding 60 °C, as the free hydroxyl attacks the ester carbonyl, producing acrylate-terminated oligomers that permanently sequester the catalyst. Consequently, the viable substrate scope for Stetter-type 1,4-dicarbonyl construction is restricted to enones and nitroalkenes unless the hydroxyl is protected in advance by silylation; even inline silylation with N,O-bis(trimethylsilyl)acetamide at 1.05 eq adds a processing step but recovers catalyst activity for ethyl acrylate coupling with benzaldehyde, achieving a 71% isolated yield of ethyl 2-benzoylpropanoate after 24 h at 40 °C under strict moisture exclusion (dew point ≤ −40 °C).What Limits Leveler Performance in Blind Microvia Copper Fill?For acid copper plating electrolytes operated at a cupric ion concentration of 40–60 g/L Cu²⁺ and a sulphuric acid concentration of 180–220 g/L, the bromide salt functions as a suppressor-modulating leveler when dosed in the 3–18 mg/L range, working in concert with an inhibitor such as polyethylene glycol (Mw 6000–8000, 200–400 mg/L) and the standard accelerator bis-(3-sulfopropyl) disulfide (SPS, 1–3 mg/L). Cyclic voltammetry stripping on a rotating disc electrode (Pt RDE, 2500 rpm, scan rate 100 mV/s) reveals that the thiazolium compound shifts the copper deposition overpotential by an additional 65–85 mV relative to the PEG baseline, indicating strong chemisorption on surface sites with high secondary current density. In this three-component additive system, the leveler’s role is to decelerate copper growth at the board surface and along the via rim during blind microvia filling (via diameter 100–150 µm, aspect ratio up to 1.5:1), relying on its mass-transport-limited convection-dependent adsorption. A persistent failure mode at production scale—observed in continuous vertical plating lines using insoluble anodes and air sparging at 2–3 L/min per tank—is the onset of foam-related pump cavitation when the hydroxyethyl-substituted thiazolium leveler exceeds 20 mg/L and the bath temperature falls below 23 °C; the hydrophilic tail reduces surface tension to 48–52 mN/m (Wilhelmy plate, Krüss K100), and the resulting microbubble foam collapses unevenly, causing oscillating current density readings that generate a sawtooth defect pattern on filled vias. IPC-TM-650 method 2.2.17.2 cross-section analysis then shows centre-line voids and a dimpling ratio above 130%, well outside the 90–110% target. The operational window is therefore constrained to 5–15 mg/L with bath temperature held at 25 ± 1 °C and minimal agitation; this counteracts the ideal hydrodynamic regime for suppressor–accelerator separation, forcing a compromise that limits maximum via filling throughput to approximately 0.7–0.9 panelfeet per minute on a horizontal conveyorized line equipped with eductor nozzles delivering 25–35 lpm per module. Published data for this exact thiazolium bromide in copper electrodeposition is scarce, but comparative Hull cell tests with analogous N-alkyl thiazolium salts (267 mL standard cell, 2 A applied for 10 min) indicate that the hydroxyethyl derivative narrows the bright working range only when the total organic carbon loading is kept below 45 ppm; above this threshold, passivation of the phosphorized copper anode surface is frequently observed, correlated with an anode potential rise beyond 0.9 V vs. Ag/AgCl.Controlling Exotherm Onset in Anhydride-Epoxy PrepregsWhen blended at 0.5–2.0 phr into a stoichiometric diglycidyl ether of bisphenol-A (DGEBA, EEW 185–192 g/eq) and methylhexahydrophthalic anhydride (MHHPA, AEW 168 g/eq) formulation, the thiazolium bromide acts as a thermally latent accelerator that does not initiate gelation below 110 °C during B-staging. Differential scanning calorimetry (DSC, ISO 11357-2:2022, 10 K/min ramp under N₂) reveals a strong catalytic effect: the exotherm onset shifts from 178 °C for the unaccelerated resin to 148 °C at 1.0 phr loading and to 136 °C at 2.0 phr, while the peak temperature drops from 202 °C to 164 °C (see representative data below). The hydroxyl functional group participates in epoxy ring-opening etherification during the first heating ramp, generating a more hydrophilic polyether network early in the cure, which in turn solubilizes the quaternary ammonium bromide and triggers an autocatalytic acceleration beyond a conversion of approximately 40%. This behaviour imposes a strict processing constraint for multilayer board prepreg manufacturing: on a typical treater tower with a residence time of 2–3 minutes at 150 °C in the heating zone, a varnish containing 2.0 phr of the catalyst exceeds a B-stage resin flow of 15% (IPC-TM-650 2.3.17) and reaches 25% gel fraction on the carrier web, leading to brittleness and dusting during slitting. Consequently, the formulation window is limited to ≤ 1.0 phr when the treater top temperature is 145–155 °C, and no hold zone is allowed. Rheologically, the complex viscosity at 130 °C measured by parallel-plate oscillation (10 rad/s, 1% strain, Anton Paar MCR 302) shows a gel point (tan δ = 1) at 127 °C for the 1.0 phr system, contrasting with 168 °C for the uncatalyzed anhydride cure, enabling a tighter cure schedule of 30 min at 150 °C followed by 2 h at 175 °C. The cured network achieves a glass transition temperature (DMA, 1 Hz, 3 K/min, ASTM D7028-17) of 152 °C, with a peak tan δ width at half height of 12 K, indicating a homogeneous network despite the catalytic cycle being intimately dependent on the distribution of the quaternary ammonium ion during the initial melt phase.
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The free alcohol 4-methyl-5-thiazoleethanol is a viscous liquid with marked hygroscopicity at relative humidities above 45%. In dry seasoning blends containing salt, maltodextrin, and monosodium glutamate, the alcohol absorbs atmospheric moisture within 48 hours of open-container exposure at 25 °C/60% RH, causing particle agglomeration and a reduction in flow function coefficient to <3 (Schulze RST-XS annulus shear cell). The bromide salt remains free-flowing under identical conditions, with a critical relative humidity of 68% and an unconfined yield strength measured at 0.8 kPa (60% RH), compared to 2.4 kPa for the free alcohol. On a production-scale tumble drum seasoning line (drum speed 15–20 rpm, seasoning dosage 2–8% w/w), loss-in-weight feeders dispense the bromide salt without the bridging and rat-holing failures encountered with the free alcohol. When the bromide salt is incorporated directly into cornmeal dough for co-extruded filled snacks processed through a twin-screw extruder (Bühler L/D 30:1, barrel profile 130–160 °C, screw speed 300–450 rpm), the crystal lattice withstands the initial thermal ramp but undergoes ion exchange with melt-phase components. Inline slit-die rheometry indicates a 5–8% reduction in melt viscosity at 140 °C versus the same formula containing the free alcohol, sufficient to shift specific mechanical energy input and alter radial expansion; barrel temperature in the final zone is therefore reduced by 5–10 °C to restore target bulk density of 50–80 g/L. Accelerated shelf-life testing (35 °C, dark, 24 months) in high-barrier laminate packaging (OTR ≤5 cm³/m²·day·atm) shows the bromide salt retains >90% of original odor activity, while the free alcohol loses 20–30% of volatile aroma compounds over 12 weeks, primarily via oxidative dimerization and evaporative surface loss.
Thermal decomposition of 3-ethyl-5-(2-hydroxyethyl)-4-methylthiazole bromide in low-moisture baked goods follows first-order kinetics, with a rate constant doubling approximately every 10 °C above 120 °C. Differential scanning calorimetry (ASTM E2046) reveals an endothermic melt at 95–98 °C and an exothermic decomposition onset at 175–185 °C, yet substantial volatile loss occurs well below catastrophic breakdown due to sublimation of the dissociated alcohol. In rotary-molded cracker baking, where surface temperatures reach 140–160 °C for 3–5 minutes, direct dough-side addition of unprotected bromide salt yields aroma retention of ≤30%. Encapsulation by spray drying with an OSA-modified starch–maltodextrin (DE 10–12) matrix at a wall-to-core ratio of 4:1 elevates survival to 65–75%, as quantified by solvent extraction and GC-MS. The encapsulant glass transition temperature (Tg) must remain above the maximum dough surface temperature; matrices with a Tg below 80 °C undergo premature collapse and release flavor into the charring zone, generating bitter off-notes. An optimized capsule delivering a Tg of 85–90 °C (DSC midpoint, 10 °C/min) is specified for band ovens operating at 180–220 °C. Dough farinograph behavior (ISO 5530-1) remains unchanged at a salt addition of 0.02% flour basis, but dissociation-liberated HBr hydrolyzes sucrose to invert sugar locally at the crust, accelerating non-enzymatic browning and shifting the CIE L* value downward by 3–5 units. This darkening must be compensated in product specification limits, where a tolerance of ±2 L* units against a target of 65 is common.
In oil-in-water flavor emulsions for ready-to-drink beverages or liquid seasoning concentrates, the bromide salt’s full water solubility confines it to the continuous phase until dilution or pH adjustment triggers dissociation—a delayed-release mechanism not achievable with the oil-soluble acetate ester. Emulsification via a high-pressure homogenizer (two-stage, 250/50 bar) yields a mean droplet diameter (D4,3) of 0.8–1.2 µm (ISO 13320 laser diffraction). The Ostwald ripening rate, ω, computed from the Lifshitz-Slyozov-Wagner linear increase of r³ with time, is 2–3 times lower for systems containing the bromide salt versus those loaded with the acetate ester at equimolar active alcohol concentration, owing to the negligible solubility of the salt in the oil droplet interior. 12-month real-time stability monitoring (25 °C/60% RH) confirms a D4,3 shift of <0.2 µm for the bromide system against 0.6 µm for the acetate system. Weighting agents (sucrose acetate isobutyrate at 0.1–0.2 wt% of oil) remain necessary to supress creaming, but the bromide salt’s low oil-phase diffusion diminishes the driving force for droplet coarsening. The odor threshold of the liberated alcohol in a neutral beverage (pH 6.8) is reported as 0.2–0.5 ppb (ASTM E679); typical use levels of the bromide salt are consequently 0.01–0.05 ppm w/w of finished product.A comparative shear-cell study of spray-dried seasoning powders containing the bromide salt versus the free alcohol established a critical relative humidity (CRH) of 68% versus 45% at 25 °C. The unconfined yield strength at 60% RH rose from 0.8 kPa (bromide) to 2.4 kPa (free alcohol), triggering cohesive arching in conical hoppers with outlet diameters below 300 mm. In a 5-tonne silo discharging through a 300 mm rotary valve, the bromide formulation sustains a mass flow rate of 600 kg/h at ambient RH up to 65% without flow aids; the free-alcohol blend requires intermittent pneumatic hammer activation and exhibits a throughput reduction of 30–40% beyond 50% RH. This difference eliminates the need for anti-caking agents such as fumed silica, which can push respirable dust concentrations above the 5 mg/m³ workplace exposure limit referenced in several regional occupational exposure standards. On vertical form-fill-seal packaging machines operating at 60–80 bags/min, the improved flow consistency reduces seal-contamination downtime by 12–15% over an 8-hour shift.
Aqueous casing solutions for reconstituted tobacco sheet and cut-rag application, typically containing inverted sugar, licorice extract, and cocoa powder at 60–70% solids, are applied at 2–4% by weight. The coated web passes through a tunnel dryer with surface temperatures of 110–130 °C for 3–7 minutes. The bromide salt remains dissolved in the casing liquid and does not volatilize until thermal dissociation above 120 °C; the free alcohol, with a vapor pressure estimated at 0.5 Pa at 25 °C, loses 40–60% of its mass during drying. The acetate ester (b.p. approx. 270 °C) exhibits better retention but its hydrophobic character causes uneven distribution in the dry casing film, producing localized vegetal-green notes divergent from the target roasted-nut profile. The bromide salt’s uniform aqueous dispersion ensures a consistent smoke aroma, as confirmed by triangular sensory difference tests (ISO 4120). At use levels of 0.5–2 mg/kg finished tobacco, the salt does not influence burning rate or ash cohesion, provided residual bromide remains below 150 ppm to avoid smoldering anomalies. By contrast, the free alcohol at equivalent sensory contribution increases moisture retention in the tobacco rod, widening puff count variability beyond the acceptable ±8% target.
The table summarizes key physicochemical and sensory parameters that distinguish the bromide salt from its structural analogues.
| Parameter | 3-Ethyl-5-(2-hydroxyethyl)-4-methylthiazole bromide | 4-Methyl-5-thiazoleethanol (free alcohol) | 4-Methyl-5-thiazoleethanol acetate | 2-Ethyl-4-methylthiazole |
|---|---|---|---|---|
| Physical form at 25°C | Crystalline powder | Viscous liquid | Low-viscosity liquid | Liquid |
| Molecular weight (g/mol) | 252.17 | 143.21 | 185.24 | 127.21 |
| Melting point (°C) | 95–98 | −20 (pour point) | −15 | −40 |
| Water solubility (g/L at 25°C) | >50 | 15–20 | Insoluble | 2–3 |
| Odor threshold in water (ppb) [ASTM E679] | 0.2–0.5* | 0.2–0.5 | 0.5–1.0 | 10–20 |
| Typical use level in food (ppm) | 0.01–0.1 | 0.01–0.1 | 0.05–0.2 | 0.5–2.0 |
| Dry storage stability (headspace loss, 35°C/12w) | <10% | 20–30% | 15–20% | Not applicable |
*Threshold reported for the dissociated alcohol; the bromide salt is non-volatile prior to hydrolysis.
The regulatory status of 3-ethyl-5-(2-hydroxyethyl)-4-methylthiazole bromide in flavor applications is primarily that of a dissociable processing aid yielding 4-methyl-5-thiazoleethanol, a substance listed under FL-no. 15.125 in Annex I of EU Regulation 1334/2008 and recognized as FEMA 3892. The free alcohol has been evaluated by JECFA and is permitted at quantum satis levels in most food categories. The bromide salt, when used as a precursor in thermal process flavourings governed by Article 9 of Regulation 1334/2008, must undergo complete counterion exchange with endogenous food anions—chloride, lactate, citrate—to keep residual inorganic bromide below the functional limit established in CODEX STAN 192-1995. Producers of reaction flavours achieve this by maintaining a molar excess of sodium chloride (2:1 chloride-to-bromide) and holding the reactor mass at 100–110 °C for 60 minutes; residual bromide in the finished flavouring is then typically below 50 mg/kg. The acetate ester avoids this counterion constraint entirely, yet confers no storage-stability benefit over the free alcohol and does not offer the same controlled-release pathway in aqueous food matrices. In the manufacture of reaction-based meat process flavours (Type I, IOFI classification), the bromide salt is charged into a glass-lined reactor (500–1000 L) alongside a protein hydrolysate (degree of hydrolysis 15–25%), reducing sugars (xylose, glucose), and animal fat. The pH is adjusted to 5.5–6.0 with 1 N NaOH. The mass is heated to 100–110 °C and held under reflux with agitation at 80–120 rpm for 45–120 minutes. The salt dissociates within 10–15 minutes, releasing the thiazole alcohol into the Maillard cascade to generate roasted, meaty, and sulfurous notes. A process conflict arises from the liberation of HBr, which drops the system pH by 0.2–0.5 units; uncorrected, this drives pyrazine formation at the expense of thiazole intensity. Inline pH monitoring with incremental NaOH addition is required to maintain the setpoint, a practice validated by GC-Olfactometry of the distillate. An additional processing boundary concerns aldehyde-rich formulations: co-addition with acetaldehyde or propionaldehyde during the initial heating phase diverts the reaction pathway toward Strecker degradation byproducts such as 2,3-butanedione, potentially reducing the yield of target 5-hydroxyethyl-4-methylthiazole species by up to 40%—a figure extrapolated from model system studies, as published data for this exact configuration remain limited. A delayed introduction protocol, adding the bromide salt after the first 30 minutes of reaction, mitigates this interference and preserves the intended roasted-meat character.
