N-Methyl-2-Acetylpyrrole
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HS Code |
790469 |
| Chemical Formula | C7H9NO |
| Molecular Weight | 123.152 g/mol |
| Appearance | Liquid |
| Boiling Point | 197 - 198 °C |
| Density | 1.038 g/mL at 25 °C |
| Flash Point | 76 °C |
| Solubility In Water | Slightly soluble |
| Refractive Index | 1.513 - 1.515 |
As an accredited N-Methyl-2-Acetylpyrrole factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 100g of N - Methyl - 2 - Acetylpyrrole packaged in a sealed, chemical - resistant bottle. |
| Shipping | N - Methyl - 2 - Acetylpyrrole is shipped in properly sealed containers, adhering to chemical transportation regulations. Shipment may involve road, rail, or sea transport, ensuring product integrity during transit. |
| Storage | N - Methyl - 2 - Acetylpyrrole should be stored in a cool, dry, well - ventilated area, away from heat sources and open flames. It should be kept in a tightly sealed container to prevent evaporation and exposure to air or moisture. Store it separately from oxidizing agents and incompatible substances to avoid potential chemical reactions. |
Liquid-phase incorporation into confectionery and baked-goods matrices demands rigorous pre-dispersion to prevent localized over-concentration that manifests as bitter metallic off-notes detectable at concentrations exceeding 60 ppm in finished chocolate. N-Methyl-2-Acetylpyrrole (CAS 932-16-1, FEMA 3184, JECFA 1452) exhibits a log Pow of approximately 1.2, rendering it partially miscible in both lipid and aqueous phases; this amphiphilic character is exploited by preparing a 10% (w/w) stock solution in triacetin or benzyl alcohol prior to blending into molten cocoa butter at 45–50°C. The addition level in standard milk chocolate containing 30% total fat typically ranges from 8 ppm to 25 ppm, with upper thresholds dictated by the emergence of a sharp pyrrole-like pungency rather than the desired caramel-nutty signature. Conching cycles at 55–70°C for 12–24 h further homogenize the flavorant and facilitate volatilization of residual solvent, a step confirmed via SPME-GC-MS monitoring of headspace acetylpyrrole concentration. For baked applications such as cookies and crackers, the compound is often sprayed onto the dough surface as a diluted emulsion (0.1% active in vegetable oil) post-baking to minimize thermal degradation, given that differential scanning calorimetry reveals an exothermic decomposition onset near 215°C which exceeds typical oven core temperatures but may be approached in thin, crisp products.What controls the dose-response of N-Methyl-2-Acetylpyrrole in clear beverage systems?Sensory threshold data obtained via ASTM E679-19 forced-choice ascending concentration series places the orthonasal detection limit in still mineral water at 1.8 µg/L and the recognition threshold at 5.4 µg/L. At dilution levels below 10 ppb, the compound supplies a subtle roasted-coffee backdrop without identifiable character, while concentrations exceeding 45 ppb risk a phenolic cresol-like defect in cola-type phosphoric-acidified matrices (pH 2.5–2.8). Carbonation introduces an additional variable: CO₂-induced turbulence in the headspace amplifies volatility, effectively lowering the organoleptic threshold by an estimated 20–30% compared to still beverages, a factor routinely compensated by reducing the dosing rate to 2–8 ppb in canned nitrogen-infused cold-brew coffees. Regulatory compliance for beverage use within the EU is governed by Regulation (EC 1334/2008), where N-Methyl-2-Acetylpyrrole is listed as a flavoring substance in Category 14.1.4 (flavoured drinks), with no numerical maximum use level specified under the “quantum satis” principle; however, Finished Product Release protocols under FSSC 22000 commonly cap total added flavor at 0.001% (10 mg/kg) as an internal quality gate. Production-scale batch preparation proceeds by injecting a pre-filtered (0.22 µm) alcoholic solution (95% v/v ethanol) directly into the syrup phase at 10–15°C under slow agitation (200–300 rpm) prior to final mixing with carbonated water, a sequence that avoids precipitation observed when the neat ester is injected post-carbonation.Dough-based and extruded cereal products pose a mass-transfer challenge because the starch-protein matrix traps volatile flavor molecules, reducing their headspace availability during mastication. Encapsulation inside oxidized starch granules (particle size D90 < 100 µm) containing 5–15% load of N-Methyl-2-Acetylpyrrole has been adopted in continuous mixer lines with residence times under 90 seconds. The encapsulate is added at 0.05–0.15% of dry flour weight, and scanning electron micrographs confirm that the glassy shell remains intact during kneading at moisture levels below 22%, rupturing only upon thermal expansion in the oven or extruder barrel. Twin-screw extruders configured with a L/D ratio ≥ 32 and barrel temperature profile climbing from 80°C (zone 1) to 160°C (die) register an inline FTIR absorbance shift at 1680 cm⁻¹ (acetyl carbonyl stretch) when the shell breaches, allowing real-time process verification. A distinct limitation emerges if the dough pH falls below 5.0 — levels often found in sourdough formulations — because acid-catalyzed ring hydrolysis generates 2-acetylpyrrole and dimethylamine, the latter imparting an ammoniacal taint that overpowers the intended caramel top note.Tobacco Casing and Top Flavor Incorporation: Pyrolytic Stability ThresholdsN-Methyl-2-Acetylpyrrole contributes to the nutty-caramel facet of flue-cured Virginia-style cigarette filler and pipe tobacco, where it is customarily applied through the casing sauces intimately mixed before cutting or through top-dressing flavors sprayed onto finished cut lamina. Addition rates in casing liquor (which comprises sugars, humectants, and licorice extracts) range from 0.5 ppm to 3.0 ppm on a dry-tobacco-weight basis, with the lower boundary reserved for high-sugar brightleaf and the upper boundary for low-grade burley that demands aggressive flavor compensation. Stability at combustion-zone temperatures (600–950°C) is inherently limited: authentic pyrolysis-GC×GC-TOFMS traces show that approximately 60–70% of the parent molecule is destroyed during smolder, generating by-products that include 1-methylpyrrole, 2-methylpyrazine, and traces of hydrogen cyanide via ring fragmentation, although the minor contribution remains far below toxicological concern under WHO TobReg 9 inventory thresholds. For heat-not-burn sticks operating at 250–350°C, the thermal survival rate climbs to roughly 85%, which has driven a shift toward this format where the pyrrole esters are coated onto purified microporous cellulose acetate tow using an electrostatic spinning process (15–20 kV, 0.5 mL/h feed rate) to achieve uniform distribution. Regulatory filing under the FDA’s Substantial Equivalence pathway typically requires reporting analytical batch data for N-Methyl-2-Acetylpyrrole with a limit of quantification (LOQ) of 0.1 ng/cig via UPLC-MS/MS in selected reaction monitoring mode.When warm roasted notes replace synthetic musk in functional fragrancesThe shift toward gourmand accords in fine and functional perfumery has positioned N-Methyl-2-Acetylpyrrole as a low-odor-threshold replacer for partially restricted polycyclic musks, particularly in shampoo and liquid laundry detergent formulations where its high dilution factor (1–5% in dipropylene glycol) yields cost-in-use advantages. Perfume concentrate additions of 0.05–0.4% are typical; surpassing 0.5% in an anionic surfactant base (sodium laureth sulfate, 10–15% active) triggers a phase-separation zone mapped with a ternary diagram of water-surfactant-flavorant that generates an opaque halo and leads to sedimentation within 48 h at 40°C in accelerated stability chambers following IFSCC Monograph No. 10 guidelines. The compound’s Schiff-base-forming potential with residual aldehyde cologne ingredients — citronellal and lyral in particular — requires chelation via EDTA tetrasodium (0.05%) in the aqueous phase when creating transparent eau-de-toilette preparations with ethanol content below 80% v/v. For powdered laundry detergents, a spray-dried slurry process embeds the fragrance within sodium sulfate carrier beads at 120°C inlet/ 70°C outlet air temperatures; GC-Olfactometry profiling of the headspace above washed fabrics reveals that the caramel-roasted character persists through rinse cycles and line-dry, with a decay half-life of approximately 18 h under ambient indoor conditions.The pyrrole ring as a C-2 functionalization scaffold in heterocyclic synthesisPyrrole derivatives bearing an acetyl group at the 2-position and a methyl substituent on the nitrogen are utilized as synthetic intermediates for constructing fused bicyclic systems via Vilsmeier-Haack formylation or Friedel-Crafts acylation at the remaining electron-rich C-5 or C-3 positions. N-Methyl-2-Acetylpyrrole serves here as a bifunctional building block: the acetyl carbonyl undergoes Wittig olefination to yield alkenylpyrroles employed in Diels-Alder [4+2] cycloadditions with maleic anhydride to produce tetrahydroindole pharmacophores, while the N-methyl group directs electrophilic attack with a regioselectivity ratio exceeding 9:1 in favor of C-5 substitution under nitration conditions (HNO₃-Ac₂O, −10°C). Kilolab batch records accessed from CRO scouting reports indicate that the Claisen condensation of N-Methyl-2-Acetylpyrrole with ethyl formate in the presence of sodium hydride (2.5 eq) in anhydrous THF at 0–5°C furnishes the corresponding β-ketoaldehyde in yields of 72–78% after vacuum distillation (112–115°C at 4 mbar). The primary limitation involves competing N-demethylation when exposed to Lewis acids such as BBr₃ or AlCl₃ at temperatures above 40°C, which liberates 2-acetylpyrrole and necessitates a re-protection step; hence, synthetic routes requiring such catalysts are preferentially replaced by TsOH-mediated acetal protection strategies that preserve the N-alkyl group throughout the sequence.Meat-analogue and process-flavor reaction engineering exploits the thermal generation of heterocyclic aromas from this pre-formed pyrrole nucleus via Maillard-type cascades. A pre-reacted process flavor base is produced by blending N-Methyl-2-Acetylpyrrole (0.2–1.0% of total reactant mass) with reducing sugar sources (xylose or glucose, 3–5 parts) and cysteine hydrochloride (1 part) in a jacketed vessel held at 125°C for 45–60 min under pH 6.0–6.5, buffered by secondary phosphate. The resulting dark-brown paste develops characteristic roasted-meaty-nutty notes, analytically correlated with increased pyrazine-to-pyrrole ratios exceeding 0.8 as determined by GC-FID area percent. In high-moisture extrusion texturization of soy protein concentrate (65% moisture), this flavor base is injected post-extruder through a water-cooled injection port (30–40°C) at 0.3–0.5% w/w, avoiding the barrel residence zone above 140°C where the acetyl group would undergo premature cleavage and evaporative loss. Sensory panel responses (n=24, trained using Spectrum Descriptive Analysis per ASTM STP 758) assign the resulting fibrous strips a mean “roasted onion/caramelized meat” intensity of 4.7 on a 15-point universal scale, compared to 2.1 for the unflavored control, validating the contribution of the N-methyl-2-acetyl precursor to non-vegetal savory character without the sulfur-dominated pungency that often limits consumer acceptance in plant-based burgers.
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In synthetic organic chemistry, the pyrrole scaffold provides a versatile entry point for heterocyclic elaboration, yet the selective introduction of acyl and N-alkyl substituents often dictates downstream reactivity and physicochemical profile. N-Methyl-2-acetylpyrrole (CAS 932-16-1) combines a methyl substituent on the ring nitrogen with an acetyl moiety at the 2-position, yielding a pale yellow to amber liquid with a molecular weight of 123.15 g·mol⁻¹. Commercially, the compound is supplied as a ≥97.0% (GC) assay material, with typical lot-specific parameters: refractive index nD20 1.5340–1.5390, density 1.030–1.050 g·cm⁻³ at 20 °C, and a boiling range of 83–87 °C at 10 mmHg. This product is differentiated from unsubstituted 2-acetylpyrrole by a significantly suppressed N–H hydrogen-bond donor capacity, which alters both volatility and solvation behavior. Unlike 2-acetylpyrrole (mp 85–87 °C, bp 220 °C), the N-methyl derivative remains liquid under ambient conditions, facilitating liquid-phase dosing in continuous-flow reactors. A direct comparison of key physical properties across structurally related acetylpyrroles is essential for rational solvent selection and process optimization.
| Property | N-Methyl-2-acetylpyrrole | 2-Acetylpyrrole | N-Ethyl-2-acetylpyrrole |
|---|---|---|---|
| CAS | 932-16-1 | 1072-83-9 | 39741-41-8 |
| Molecular Formula | C₇H₉NO | C₆H₇NO | C₈H₁₁NO |
| Physical State (20°C) | Liquid | Low-melting solid | Liquid |
| Boiling Point (°C) | 83–87 (10 mmHg) | 220 (760 mmHg) | 101–104 (10 mmHg) |
| Refractive Index (nD20) | 1.534–1.539 | solid | 1.528–1.533 |
| Typical GC Purity (%) | ≥97.0 | ≥98.0 | ≥96.0 |
| Primary Differentiation | Balanced N-alkyl/acyl; liquid handling | Strong H-donor; divergent H-bonded crystal packing | Higher boiling point; slower vapor diffusion |
In flavor and fragrance compounding, the vapor-liquid partition coefficient of a heterocyclic ketone fundamentally determines its headspace impact and sustained release profile. N-Methyl-2-acetylpyrrole exhibits a popcorn-like, roasted, and slightly nutty organoleptic character, but its performance diverges sharply from that of 2-acetylpyrrole in hydroalcoholic solutions above 40% ethanol by volume. Because the N–H proton of 2-acetylpyrrole participates in intermolecular hydrogen bonding with water and ethanol, its activity coefficient remains suppressed, requiring higher dosage for equivalent aroma impact. The N-methylated analog lacks this hydrogen-bond donor capacity; consequently, its air–liquid partitioning measured via headspace GC–MS under static equilibration at 37 °C shows a 1.8- to 2.3-fold increase in headspace concentration at equal molar loading, as per the EPI Suite HENRYWIN v3.20 estimation method and corroborated by experimental phase ratio variation data reported in flavor research literature. Processing teams operating spray-drying encapsulation on a Niro Minor™ unit with inlet temperature 180 °C should anticipate higher volatile losses during atomization if the carrier matrix (e.g., gum arabic/maltodextrin DE 10) is not pre-loaded with an oil-phase entrapment agent such as medium-chain triglyceride (MCT) at a core-to-wall ratio of 1:4. Published data for the exact retention of N-methyl-2-acetylpyrrole under industrial spray-drying conditions is limited; however, extrapolation from the behavior of structurally analogous N-alkylpyrroles suggests an encapsulation efficiency ceiling of approximately 65–70% without lipid partitioning aids, compared to 80–85% for 2-acetylpyrrole in identical matrices due to the solid’s lower vapor pressure.
N-Methyl-2-acetylpyrrole has been evaluated as a film-forming electrolyte additive in lithium-ion cells employing LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes. The acetyl group is susceptible to oxidative ring-opening at potentials exceeding 4.35 V vs. Li/Li⁺, which generates a passivating oligomeric layer on the cathode surface. However, practical implementation on pilot-scale pouch cells (3 Ah) has revealed that N-methyl substitution lowers the oxidation onset by approximately 120 mV relative to N–H 2-acetylpyrrole, shifting the onset into the upper edge of standard charging protocols (4.2–4.3 V). Formation cycling at C/10 rate with 1.0 wt% additive in 1.0 M LiPF₆ EC/EMC (3:7 v/v) results in a 9–12% irreversible capacity loss in the first cycle, primarily due to excessive film growth. The additive is incompatible with electrolyte formulations containing >1.0 wt% fluoroethylene carbonate (FEC), as the FEC radical polymerization competes with acetylpyrrole oligomerization, leading to a non-uniform, high-impedance interphase. Further, moisture content in the electrolyte must be maintained below 15 ppm (Karl Fischer titration, ASTM E1064-12), because hydrolytic ring-opening of the acetylpyrrole generates colored byproducts that increase the UV absorbance at 380 nm beyond acceptable limits for spectroscopic quality control in continuous metering lines. No long-term cycling data at 45 °C beyond 200 cycles has been released in publicly accessible technical bulletins for this specific N-methyl congener.
The electron-withdrawing acetyl group at C2 and the electron-donating N-methyl group establish a polarization pattern conducive to inverse-electron-demand cycloadditions. In reactions with tetrazines, N-methyl-2-acetylpyrrole reacts at the C4–C5 π-bond with a second-order rate constant of 0.032 M⁻¹s⁻¹ in acetonitrile at 25 °C, measured via stopped-flow UV/Vis monitoring of tetrazine consumption at 520 nm. This rate is roughly 40% higher than that of N–H 2-acetylpyrrole under identical conditions, a difference attributed to the enhanced nucleophilicity of the pyrrole ring induced by the N-methyl group (Hammett σp for N–CH₃ vs. N–H estimated at −0.15). On scale, batch reactions performed in a 5 L jacketed glass reactor with a retreat-curve impeller at 300 rpm require strict temperature control at 0–5 °C during tetrazine addition to avoid a thermal excursion exceeding +8 °C, which leads to the formation of regioisomeric adducts detectable by 1H NMR at δ 6.8 and 6.5 ppm in a 3:1 ratio. The N-methyl analogue offers a processing advantage over 2-acetylpyrrole because its liquid state eliminates the need for pre-dissolution in dichloromethane or THF, reducing the solvent inventory and simplifying work-up; however, oxidative degradation of the product during silica gel chromatography is more pronounced, requiring the addition of 0.5% v/v triethylamine to the eluent (hexane/ethyl acetate 4:1) to suppress tailing.
Direct utilization of N-methyl-2-acetylpyrrole as a building block in the synthesis of pyrrolo[2,1-f][1,2,4]triazine kinase inhibitors has been demonstrated at the medicinal chemistry scale. The N-methyl group remains intact through a sequence involving Vilsmeier–Haack formylation at C5 and subsequent condensation with amidrazones, yielding intermediates with IC50 values in the low nanomolar range against JAK2. Notably, the absence of an N–H proton simplifies the final deprotection strategy, as there is no need for a Boc or SEM protecting group on the pyrrole nitrogen. Published data for this specific configuration is limited to milligram-scale synthesis; no pilot-plant campaigns have been reported in open literature.
Fractional distillation of N-methyl-2-acetylpyrrole under vacuum (10 mmHg) using a wiped-film evaporator with an internal condenser at 90–105 °C jacket temperature provides product of acceptable purity, yet several thermal hazards must be managed. Differential scanning calorimetry (DSC) at a heating rate of 5 °C·min⁻¹ (ASTM E537-20) reveals an exothermic decomposition onset at 215 °C, with an energy release of approximately 480 J·g⁻¹. This onset is 25 °C lower than that of 2-acetylpyrrole, likely due to N-demethylation initiating a radical chain pathway. Accumulation of pot residue beyond 8 hours at processing temperature leads to viscosity build-up and eventual charring; a thin-film evaporator with a residence time below 2 minutes is therefore mandatory for scale-up beyond 20 L capacity. The distillate must be stored under nitrogen blanket and protected from light (amber glass or HDPE with UV barrier), as exposure to 365 nm radiation for 48 hours increases the peroxide value from <0.5 meq/kg to 8.2 meq/kg, accompanied by the formation of a dark red chromophore absorbing at 470 nm. Incompatibility with strong bases (NaOH 20% at 60 °C) results in rapid ring-opening and tar formation; neutral or mildly acidic conditions must be maintained during aqueous washes.
N-Methyl-2-acetylpyrrole is listed on multiple chemical inventories, including TSCA, EINECS (213-422-3), and PICCS, enabling trans-Pacific commerce without prior notification. For flavor applications, it falls under FEMA 3184 and has been evaluated by the JECFA; the most recent safety assessment (EFSA, 2011) concluded that it poses no safety concern at estimated dietary intake levels up to 0.5 µg/person/day. Users must confirm that the specific lot complies with the EU Flavourings Regulation (EC) 1334/2008, Annex I, and verify that residual solvent levels (typically ethyl acetate <50 ppm) fall within the limits of Directive 2009/32/EC. In pharmaceutical intermediate supply, DMF support varies by manufacturer and should be confirmed directly. Standard packaging comprises 5 kg and 25 kg UN-approved HDPE drums with nitrogen headspace, or 200 kg steel drums for bulk orders. Due to its liquid nature and 1.03 g·cm⁻³ density, the material can be transferred via positive displacement pump without the melting and heat-tracing infrastructure required for 2-acetylpyrrole solids, reducing capital expenditure on multi-purpose production lines in GMP kilo-lab suites.
