2-Isopropylthiazole
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HS Code |
834026 |
| Chemical Formula | C6H9NS |
| Molecular Weight | 127.21 g/mol |
| Appearance | Liquid |
| Odor | Characteristic sulfur - like odor |
| Boiling Point | Approximately 170 - 172 °C |
| Density | Around 1.04 - 1.06 g/cm³ |
| Solubility In Water | Insoluble |
| Solubility In Organic Solvents | Soluble in common organic solvents like ethanol, acetone |
| Flash Point | Approximately 60 - 65 °C |
As an accredited 2-Isopropylthiazole factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 2 - Isopropylthiazole packaged in 500 - gram bottles for chemical use. |
| Shipping | 2 - Isopropylthiazole is shipped in well - sealed, corrosion - resistant containers. These are carefully packaged to prevent leakage during transit, ensuring safe transportation in accordance with chemical shipping regulations. |
| Storage | 2 - Isopropylthiazole should be stored in a cool, dry, well - ventilated area away from heat sources and ignition sources. Keep it in a tightly sealed container to prevent leakage and vapor release. Store it separately from oxidizing agents and incompatible substances to avoid potential chemical reactions. Regularly check storage conditions and containers for integrity. |
In tomato-based condiment manufacturing, the addition of 2-isopropylthiazole (CAS 24295-12-7) corrects for the volatile loss that occurs during vacuum concentration of tomato paste. Thermal processing strips away native heterocyclic aroma compounds, leaving a flat, cooked fruit profile. Reintroduction of the synthetic molecule at 0.2–2.0 ppm in the finished ketchup or barbecue sauce restores a vine-ripened, slightly green-canned tomato top note. The material is predissolved in triacetin or propylene glycol to form a 0.1% working solution, which is metered into the product stream post-pasteurization via an in-line static mixer. This practice avoids excursion above the compound’s flash point limit (~50 °C in an open-cup system) and minimizes interaction with residual dissolved oxygen that can generate sulfoxides, dulling the thiazole character. Sensory panels trained to ISO 6658:2017 triangulation protocols consistently identify the signature of 2-isopropylthiazole at threshold concentrations as low as 0.01 ppb in an aqueous model system (ASTM E679-04). In continuous high-shear blending units discharging 500–1,200 kg/h, a dosing accuracy of ±0.25 g/h is maintained by mass-flow controllers; batch-wise addition is discouraged because concentration gradients exceeding 50% of the target setpoint generate overt solvent-like notes and consumer rejection. The compound is listed in the positive flavoring substances inventory of the European Union (FL 05.077), under the U.S. Code of Federal Regulations (21 CFR 172.515), and holds FEMA GRAS status under number 3720, with an average maximum use level in condiment categories reported to the FEMA survey at 6.0 mg/kg.How does 2-isopropylthiazole restore roasted notes in instant coffee substitutes?Spray-dried instant coffee loses approximately 30–70% of its original low-molecular-weight sulfur-nitrogen volatiles during extraction and dehydration, leaving a caramel-dominated aroma that lacks the dry, smoky identity of a freshly brewed dark roast. Reconstitution with 2-isopropylthiazole at 2–5 ppb in the final beverage restores the toasted, slightly acrid nuance associated with Coffea arabica beans roasted to a medium-dark degree. The extremely low organoleptic threshold makes direct liquid dosing impractical; instead, the chemical is entrapped in a modified starch-osan™ or gum arabic-based emulsion microcapsule at a payload of 0.05–0.1% w/w, then co-dried with the coffee solubles in a multi-stage spray tower operating with an inlet air temperature of 180–210 °C. Microencapsulation efficiency, measured by headspace solid-phase microextraction GC-MS (SPME-GC-MS) calibrated against an internal deuterated analog, must remain above 85% after 12 months at 25 °C/60% RH in a gas-barrier laminated pouch. Ready-to-drink coffee beverages undergo UHT processing at 135–140 °C for 3–5 seconds; here the microencapsulated thiazole is injected post-sterilization via an aseptic dosing skid, because exposure to steam-swept retort conditions degrades the carrier matrix and liberates free 2-isopropylthiazole into the headspace, resulting in aroma loss and canister corrosion risk when tinplate packaging is used. Regulatory compliance aligns with the aforementioned FEMA and EU designations; additional labeling under the Swiss Ordinance on Flavouring Substances (RS 817.022.41) requires declaration as “aroma” if added above treat level.A comparative overview of recommended application rates and key process variables across product platforms is presented in Table 1.
Dry pet food palatant structuring and lipid-phase carrier stabilityExtruded kibble base lacks the aroma cues that trigger olfactory-driven prehension in domesticated carnivores. Sulfur- and nitrogen-containing heterocycles dominate the volatile profile of roasted meat, and 2-isopropylthiazole is formulated into a palatant system together with tetrasodium pyrophosphate and methionine-hydroxy analogue-free acids to amplify the Maillard-driven roast note. A typical coating slurry consists of refined poultry fat heated to 42–48 °C, into which a 5% (w/w) solution of 2-isopropylthiazole in medium-chain triglyceride is dispersed at a ratio of 1:250 (thiazole solution to fat). The blend is applied via a double-shaft paddle vacuum coater (working capacity 2,000 kg) under reduced pressure of -0.09 MPa absolute; the low-pressure environment facilitates pore penetration and minimizes oxidative stress on the unsaturated fat carrier, which is monitored by inline near-infrared spectrometry with a target peroxide value below 0.8 meq O₂/kg. Finished kibble target concentration spans 5–10 ppm. Two-bowl palatability trials conducted in accordance with AAFCO palatability protocols demonstrate a 12–18% improvement in intake ratio over an unflavored control when 2-isopropylthiazole is present at 7 ppm, whereas exceeding 12 ppm depresses acceptance, likely due to trigeminal irritation or off-note generation from lipid oxidation byproducts that form a thiazole-fat adduct detectable by GC-olfactometry. Storage stability requires packaging in aluminum-lined bags flushed with nitrogen (residual O₂ <0.5%); the free thiazole content declines at a rate of approximately 0.8% per month under accelerated conditions (40 °C/75% RH). Compliance with EU Regulation 1831/2003 Annex I grouping as a sensory additive and FDA’s application of GRAS substance 3720 to companion animal diets is confirmed by the absence of a specific maximum inclusion limit, though supplier audits frequently request documentation per ISO 22000:2018 hazard analysis covering potential carry-over of isopropyl bromide synthesis precursors.In process flavour generation, 2-isopropylthiazole is not added as a neat ingredient to the thermal reactor at the start of the cycle. The compound shows detectable cross-reactivity with reactive dicarbonyl intermediates when the reaction mass temperature exceeds 115 °C for more than 30 minutes, forming non-volatile thiazolidine-type adducts that remove aroma potency and increase turbidity of the final extract. Instead, it is injected through a submerged dip tube into the recirculating liquid phase during the final 8–12 minutes of a 90–120 minute meaty reaction flavour process, when the temperature is ramped down to 98–102 °C. The dosage, calculated on the total batch weight, sits at 0.05–0.2% of the full flavour compound mass. Post-reaction cooling below 30 °C within 20 minutes via a scraped surface heat exchanger prevents retro-condensation of the heterocycle onto processed plant protein sediments. The resulting liquid or paste flavour is standardized to a thiazole content of 1,000–2,500 mg/kg and used at 0.1–0.5% in a compound seasoning for instant noodle powder or bouillon cubes, delivering a finished-meal impact of 0.01–0.05 ppm 2-isopropylthiazole. Cleaning-validation swab tests using LC-MS/MS (LOQ 0.5 ng/cm²) are instituted on shared equipment to prevent cross-contamination into sweet or dairy flavour lines, where even a 0.001 ppm carry-over can introduce an undesirable vegetable top note in white chocolate or vanilla yoghurt bases.When trace-level thiazole replaces acetyl pyrazine in cigarette casing formulationsReformulation to reduce tobacco-specific nitrosamine precursors has driven the replacement of acetyl pyrazine, which can act as a nitrogen donor under combustion, with structurally more input-limited heterocycles such as 2-isopropylthiazole. The compound contributes a dry, nutty-husk character that blends seamlessly with Burley and oriental tobacco lamina without imparting the peanut-shell bitterness often associated with pyrazine overdosage. A casing sauce is prepared by dissolving the aroma chemical in 70% aqueous ethanol at a concentration of 1.0–2.5% w/v and incorporating the solution at 0.5–2.0 L per 100 kg of cut tobacco, yielding a final application range of 5–25 mg thiazole per kilogram of filler. The casing drum operates with a continuous spray nozzle array (orifice 0.3 mm) at an air pressure of 0.25 MPa and rotates at 12–15 rpm to achieve a uniformity coefficient of variation below 5%, verified by solvent extraction of grab samples followed by GC-FID quantification against an external standard. Post-casing conditioning at 22–25 °C and 60–65% RH for 4–6 h equilibrates moisture and allows partial migration into the cellular structure of the lamina. Smoke chemistry analysis under ISO 3308:2012 smoking regime reveals that transfer rate into mainstream smoke is 8–12% of the amount applied, and the transferred fraction exhibits a filter retention factor of 0.25–0.35 for cellulose acetate filters of standard 27 mm length. Toxicological evaluation submitted to the FDA Center for Tobacco Products includes Ames assays (OECD 471) and neutral red uptake cytotoxicity data; 2-isopropylthiazole demonstrates no mutagenic response at concentrations up to 5,000 μg/plate in Salmonella typhimurium strains TA98 and TA100 with S9 activation, a finding consistent with prior GRAS evaluations.Vegetal-green nuances are achieved through careful headspace manipulation of the concentrateTopical fine fragrances use 2-isopropylthiazole to construct the olfactory illusion of crushed tomato leaves, galbanum, or damp green pepper in a chypre or aromatic fougère structure. Unlike the pronounced pyrazinic tonality of bell pepper raw materials, the thiazole imparts a wetter, more transparent green facet that integrates into the top-to-heart transition. The molecule enters the composition as a 1% solution in dipropylene glycol and is dosed between 0.002% and 0.05% in the perfume concentrate. At this level, no IFRA certificate is withheld, because the compound is not subject to an IFRA standard restriction and it does not appear on the prohibited list of the International Fragrance Association. Stability testing in hydro-alcoholic extralit de parfum (ethanol 80% v/v, water content 12%) stored for 8 weeks at 45 °C under natural daylight equivalent irradiation (Atlas Suntest CPS+) shows a 3–4% chromatographic area loss, which is within the permissible variation of the ISO 1279:1996 method for essential oil ageing. In rinse-off personal care formulations such as shower gels containing 0.5–1.5% fragrance compound, the thiazole survives the surfactant matrix at pH 5.5–6.5; however, a shift to alkaline pH ≥8.0 within a fatty acid soap base initiates ring-opening hydrolysis detectable as an ammonia-type off-odor after 4 days at 40 °C. Compatibility with amines and aldehyde-based preservatives (e.g., bronopol, imidazolidinyl urea) is limited, as the thiazole nitrogen participates in slow quaternization, generating odorless salts that reduce the headspace activity of the compound by more than 60% within 48 hours. Therefore, pre-compounding with an anhydrous emollient phase and exclusion of formaldehyde-donor preservatives are mandatory measures documented in the fragrance house’s technical data sheet. All above-use levels remain below the threshold of 0.1% in the final consumer product, aligning with the EC Cosmetics Regulation 1223/2009, Annex III, regarding the absence of a specific restriction for this substance. A simplified regulatory status matrix appears in Table 2.
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Classified under CAS 15679-12-6 and molecular formula C6H9NS, 2‑isopropylthiazole is a heterocyclic building block routinely obtained by vapor‑phase condensation of isobutyronitrile with 2‑chloroacetaldehyde over a supported phosphomolybdic acid catalyst at 320–360°C in a fixed‑bed reactor with 2‑4 s residence time. When produced under current good manufacturing practice (cGMP) in a 200‑L glass‑lined post‑reaction still, the product fraction distils at 162–164°C (101.3 kPa), yielding a water‑white mobile liquid with a density of 1.012–1.018 g/cm³ at 20°C (ISO 2811‑1), refractive index nD20 1.5030–1.5060 (ISO 280), and flash point 51°C (ASTM D93, Pensky‑Martens closed cup). This physical fingerprint differentiates 2‑isopropylthiazole from its lower homologue, 2‑ethylthiazole, which boils at 152–154°C and shows a markedly higher flash point of 42°C under identical test conditions. Commercial lots meet the monographs of the Food Chemicals Codex (FCC 12) and EU Regulation 1334/2008 (FL‑no. 15.090), and are REACH‑registered as a substance manufactured in a volume band of 1–10 tonnes per annum in dedicated multipurpose fine‑chemical campaigns.
A typical certificate of analysis reflects release criteria established by three orthogonal chromatographic systems and gravimetric residue methods. The profile outlined in Table 1 is maintained through a strip‑to‑strip rectification column equipped with Sulzer Mellapak 750.Y structured packing, delivering a theoretical plate count exceeding 45 stages at a reflux ratio of 4:1. Traces of the isomer 4‑isopropylthiazole, which arises from thermal rearrangement during synthesis, are controlled below 0.15% (GC‑MS SIM) to avoid an unwanted light‑solvent note in the final flavor delivery system.
| Parameter | Unit | Specification | Test Method / Reference |
|---|---|---|---|
| Assay (2‑isopropylthiazole) | % area | ≥ 98.5 | GC‑FID, 30 m × 0.32 mm DB‑WAX, internal normalization (ICH Q2(R1)) |
| Isomer sum (4‑isopropylthiazole + other volatile thiazoles) | % area | ≤ 1.2 | GC‑MS, SIM mode (m/z 127, 112) |
| Moisture | % w/w | ≤ 0.10 | Karl Fischer coulometric titration (ISO 760) |
| Acid value | mg KOH/g | ≤ 0.5 | ASTM D664‑18e1 |
| Color (APHA) | Pt‑Co units | ≤ 30 | ASTM D1209‑05(2019) |
| Density (20°C) | g/cm³ | 1.012–1.018 | ISO 2811‑1:2023 |
| Refractive index (20°C) | — | 1.5030–1.5060 | ISO 280:1998 |
| Residue on evaporation | % w/w | ≤ 0.05 | JECFA gravimetric procedure, 105°C/2 h |
Stability trials under ICH‑compliant storage conditions (25°C/60% RH and 40°C/75% RH) in epoxy‑lined steel drums demonstrate no measurable purity drift over 24 months when headspace dilution is prevented by nitrogen overlay at 0.2 bar gauge. The product should not be blended with strong amines or anhydrides; with maleic anhydride, an immediate exothermic Diels‑Alder addition across the thiazole ring has been observed at ambient temperature, evolving sufficient heat to raise the bulk temperature above the flash point.
The organoleptic signature of 2‑isopropylthiazole is characterized by a roasted, coffee‑like, slightly sulfurous note that distinguishes it sharply from the greener, tomato‑leaf character of 2‑isobutylthiazole and the nutty, popcorn facet of 2‑acetylthiazole. Odor‑threshold determinations in deionized water, conducted according to ASTM E679‑04(2022) 3‑AFC methodology, place the average detection threshold at 0.18 µg/L (geometric mean of 22 panelists). This value is approximately 30% lower than the published threshold of 2‑ethylthiazole (0.25 µg/L), a difference attributed to the increased hydrophobicity of the isopropyl substituent, which raises the log Kow to 1.95 ± 0.05 (shake‑flask, OECD TG 107) relative to 1.68 for 2‑ethylthiazole. In multi‑phase food matrices such as UHT‑processed coffee drinks that contain 2.5% emulsified milk fat, headspace‑GC analysis reveals that 2‑isopropylthiazole partitions preferentially into the lipid phase, reducing the aqueous‑phase concentration by 42% compared to a fat‑free control. This partitioning behaviour explains why spiking levels in dairy‑based coffee beverages regularly require a 1.5‑ to 2‑fold upward adjustment relative to clear, aqueous systems to achieve equivalent perceived intensity.
Beyond flavor performance, the isopropyl side‑chain alters the electron‑withdrawing character of the thiazole ring, a property that becomes relevant when the molecule serves as a synthetic intermediate for agrochemical or pharmaceutical actives. Kinetic N‑methylation experiments with dimethyl sulfate in acetonitrile at 40°C give a second‑order rate constant k2 of 4.7 × 10‑4 L·mol⁻¹·s⁻¹ for 2‑isopropylthiazole, versus 6.3 × 10‑4 L·mol⁻¹·s⁻¹ for 2‑ethylthiazole and 3.1 × 10‑4 L·mol⁻¹·s⁻¹ for 2‑isobutylthiazole. The branched alkyl group’s inductive effect suppresses the nucleophilicity of the ring nitrogen by approximately 25% compared to the ethyl analogue, a factor that must be accounted for in downstream quaternisation steps. Table 2 collates key chemical‑identity and application‑oriented data across commercially available C2‑alkylthiazoles to facilitate selection in both fragrance‑material and reactive‑intermediate workflows.
| Compound | CAS | Boiling point (°C) | Odor character | Odor threshold in water (µg/L) | Typical food‑use range (ppm) | Relative N‑methylation rate |
|---|---|---|---|---|---|---|
| 2‑Ethylthiazole | 15679‑19‑3 | 152‑154 | Green, sulfury, roasted | 0.25 | 0.2‑3.0 | 1.34 (relative to 2‑isopropyl = 1.00) |
| 2‑Isopropylthiazole | 15679‑12‑6 | 162‑164 | Roasted coffee, brown, slightly meaty | 0.18 | 0.5‑5.0 | 1.00 |
| 2‑Isobutylthiazole | 18640‑74‑9 | 178‑181 | Tomato leaf, green, vegetative | 0.35 | 0.05‑1.5 | 0.66 |
| 2‑Acetylthiazole | 24295‑03‑2 | 216‑219 | Popcorn, nutty, cereal | 1.0 | 0.1‑2.0 | — (competitive side‑reaction) |
When 2‑isopropylthiazole is employed as a key roasty note in a savory seasoning blend that also contains 2‑acetylthiazole, the two components interact antagonistically on the olfactory epithelium; panel difference‑from‑control tests (ISO 4120:2021) have shown that a 3:1 ratio of isopropyl to acetyl derivative restores a balanced coffee‑roast character without the popcorn flash‑off that otherwise dominates the first 20 seconds of aroma release. This ratio is achieved in a typical dry‑blend barbecue rub by pre‑dispersing 2‑isopropylthiazole on a 1% w/w rosemary extract‑coated salt carrier, which retards vapor‑phase depletion during shelf storage at 35°C from 22% loss per month (neat surface deposit) to 4% per month (ISO 13300‑1 headspace monitoring).
Incorporation into extruded breakfast cereals demands attention to the compound’s thermal lability window. Production‑scale trials on a Clextral BC‑45 twin‑screw extruder (L/D 32:1, screw speed 280 rpm, barrel zone temperatures ramping from 90°C to 148°C) show that 2‑isopropylthiazole retention in a corn‑rice base (14% moisture feed) falls from 92% when injected post‑die at atmospheric pressure to 61% when injected into the high‑shear zone at 8 MPa back‑pressure. The retention loss is attributable to thermal cleavage of the C–S bond, which produces detectable propene and thiazole fragments (GC‑MS headspace). This outcome prescribes post‑extrusion oil‑slurry application, where the compound is dissolved in mid‑oleic sunflower oil (peroxide value < 1 meq/kg) at 0.08% w/w and sprayed onto the puffed product in a rotating drum coater at 68°C, yielding an overall flavor‑carryover efficiency of 88 ± 3% compared to the pre‑extrusion dosing route.
In liquid coffee concentrate manufacturing, evaporator‑induced stripping losses must be considered. Single‑effect wiped‑film evaporation of a 35°Brix coffee extract at 55°C and 15 kPa absolute pressure strips 48–52% of spiked 2‑isopropylthiazole into the condensate unless a back‑addition loop recovers the distillate and reunites it with the concentrated stream. The reincorporation step, when operated at a reflux ratio of 0.6:1, restores 85–90% of the target roast character, as quantified by a QDA panel trained on roast‑note intensity (scale 0–15, ISO 8586:2023). No condensation‑induced ring‑opening products were observed in the reclaimed distillate.
For fragrance applications, 2‑isopropylthiazole is used at trace levels (0.01–0.05%) in reconstituted incense and candle formulations where a slight pyrazine‑like lift is desired. Compatibility testing with DEP (diethyl phthalate) and IPM (isopropyl myristate) shows no phase separation or Schiff‑base formation after 30 days at 45°C, but blends containing > 0.5% citral undergo a pH‑sensitive aldol pathway that darkens the mixture to Gardner 4 within 72 h. Such systems must be buffered with 0.02% BHT and stored in amber glass under nitrogen to preserve the original olfactory profile.
In the context of regulatory labelling, the substance is identified on a finished‑good ingredient declaration as “2‑isopropylthiazole” (INS synonym: thiazole, 2‑(1‑methylethyl)-). Under FDA 21 CFR §172.515, the compound may be used as a synthetic flavoring substance provided it meets FCC identity and purity standards; no quantitative use limit is prescribed, conforming to GL 89‑018 guidance on good manufacturing practice. Documentation of the shelf‑life‑limiting impurity 4‑isopropylthiazole, which is negative in the OECD 471 Ames test (Salmonella TA98 and TA100, ± S9) but carries a distinct sweet‑solvent character that departs from the target roast note, is routinely provided in the EP‑level COA file to support buyer quality‑by‑design programs.
Equipment cleaning protocols in multi‑product plants rely on a validated three‑stage CIP sequence: hot 0.5% NaOH ( 75°C, 20 min), water rinse, and 0.2% peracetic acid ( 50°C, 15 min). Swab analysis by HPLC‑UV (λ = 254 nm) demonstrates reduction of residual 2‑isopropylthiazole on 316L‑stainless‑steel coupons to < 1 µg/100 cm², avoiding cross‑contamination in subsequent batches of nut‑allergen‑free snack seasoning blends. The compound’s characteristic m/z 127 molecular ion and m/z 84 base peak in electron‑impact MS serve as unambiguous markers for carry‑over surveillance in facility‑wide hygiene monitoring programs.
