N-Methylpyrrole
|
HS Code |
174340 |
| Chemical Formula | C5H7N |
| Molar Mass | 79.12 g/mol |
| Appearance | Colorless to pale yellow liquid |
| Odor | Characteristic, somewhat pungent |
| Boiling Point | 116 - 118 °C |
| Melting Point | -63 °C |
| Density | 0.96 g/cm³ at 20 °C |
| Solubility In Water | Slightly soluble |
| Flash Point | 18 °C |
| Refractive Index | 1.481 - 1.484 at 20 °C |
As an accredited N-Methylpyrrole factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | N - Methylpyrrole in 500 - gram bottles, well - sealed for safe storage. |
| Shipping | N - Methylpyrrole is shipped in well - sealed, corrosion - resistant containers. It's transported in accordance with chemical safety regulations, ensuring proper handling to prevent leakage and exposure during transit. |
| Storage | N - Methylpyrrole should be stored in a cool, dry, well - ventilated area away from heat, sparks, and open flames. Keep it in a tightly closed container to prevent vapor leakage. Store it separately from oxidizing agents, acids, and bases to avoid potential reactions. Follow proper safety regulations to ensure its secure storage. |
What Synthetic Pathways Demand High-Purity N-Methylpyrrole for FDA-Regulated APIs?Production of 1-methylpyrrole-2-carboxylic acid and its amide derivatives, which serve as heterocyclic building blocks for kinase inhibitors and antiviral ribofuranosyl triazole scaffolds, requires N-methylpyrrole with a chromatographic purity exceeding 99.5% (GC-FID, ASTM D8379-21). The monomer is typically charged at a molar equivalent of 0.98–1.05 relative to thionyl chloride or oxalyl chloride in Vilsmeier-Haack formylation, where residual pyrrole contamination above 0.05% triggers formation of colored condensation byproducts that escape selective crystallization in downstream steps. A validated cGMP-compliant process (per ICH Q7 and 21 CFR 210) integrates vacuum distillation over calcium hydride at 20–25 mbar and a center cut collected at 112–113°C, achieving halide content below 10 ppm — a threshold critical because chloride ions poison the Pd(0) catalysts used in subsequent Suzuki-Miyaura couplings to arrive at biaryl pharmacophores. A documented batch-failure mode involves emulsion-layer formation during aqueous quenching when the N-methylpyrrole chloride content exceeds 50 ppm, extending phase-separation time to over 12 hours and reducing API yield by 8–12%. Terminal dosage forms include film-coated tablets and lyophilized vials for intravenous administration, where the final substance must satisfy residual solvent limits under ICH Q3C (N-methylpyrrole itself is not listed as a Class 2 solvent, but its presence is controlled via loss-on-drying to <50 µg/tablet). Crop Protection Intermediates and Heterocyclic Scaffold ConstructionSynthesis of N-alkylpyrrole-2-carboxamide fungicides — classified under FRAC code 7 (succinate dehydrogenase inhibitors) — begins with a Friedel-Crafts acylation of N-methylpyrrole dissolved in dichloromethane at −5 to 0°C. The stoichiometric ratio of N-methylpyrrole to chloroacetyl chloride is held at 1:1.15 to compensate for moisture-induced acyl chloride hydrolysis, and the reaction mass is quenched over 15 wt% aqueous potassium carbonate to neutralize liberated HCl before phase separation. A persistent manufacturing bottleneck on pilot-scale glass-lined reactors (jacketed, −10°C brine circulation) is uncontrolled exotherm upon catalyst addition; without a 20-minute controlled dosing ramp, temperature overshoot to +8°C produces isomeric N-acylation byproducts that co-distill at 138–142°C / 4 mmHg and require fractional rectification columns with 15 theoretical plates to remove. The intermediate 2-chloroacetyl-1-methylpyrrole is subsequently aminated and cyclized to yield the active ingredient, which is formulated as a suspension concentrate (SC) containing 480 g a.i. L⁻¹. Compliance with FAO/WHO Manual on Development and Use of Pesticide Specifications mandates that residual dichloromethane remain below 400 ppm (determined per CIPAC MT 167) and that the technical material achieve a melting point of ≥ 98°C after recrystallization from ethanol. Finished products are shipped as water-dispersible granules for foliar application on cucurbits and cereals. In flavor compounding, N-methylpyrrole identified as FEMA 3451 operates as an extremely efficient burnt-sugar and nutty note contributor. Addition levels established through GC–olfactometry-guided panel studies fall within 1–20 ppm in final consumer products, though the material is typically supplied as a 0.1% (w/w) solution in triacetin or propylene glycol to permit accurate dosing by peristaltic pumps in industrial flavor houses. Regulatory clearance requires compliance with FDA 21 CFR 172.515 (synthetic flavoring substances and adjuvants) and the FEMA GRAS reaffirmation under the FGE.502 evaluation framework; the Joint FAO/WHO Expert Committee on Food Additives has not assigned an ADI, but manufacturer specifications cap dimethylaminoethylpyrrole and pyrrole homologs at combined 0.2% by GC area to avoid rancid fishy off-notes. The downstream manufacturing operation involves blending with vanillin, maltol, and sweet cream odorants via a jacketed high-shear mixer at 40–45°C, followed by spray-drying onto a maltodextrin carrier to produce heat-stable encapsulated powders. Finished goods that incorporate this ingredient encompass confectionery coatings, ready-to-drink coffee emulsions, and high-temperature-extruded breakfast cereals, all subject to sensory shelf-life monitoring at 40°C/75% RH for 12 weeks per ASTM E2454. When Cyclic Voltammetry Deposition Replaces Spin-Coating for Flexible ElectrodesElectrochemical polymerization of N-methylpyrrole onto indium-tin oxide coated polyethylene terephthalate (ITO-PET) substrates constructs a p-doped conductive film whose pseudo-capacitive charge storage competes with hydrous RuO₂ at a fraction of material cost. A three-electrode configuration — Ag/AgCl (3 M KCl) reference, platinum mesh counter — is immersed in an aqueous bath containing N-methylpyrrole at 0.10–0.30 M and a supporting electrolyte (see table). Potentiodynamic growth between −0.2 V and +0.9 V at 50 mV s⁻¹ over 15 cycles yields a 400–600 nm thick adherent deposit; the method avoids the solvent-waste stream of spin-coating pre-formed polymers and allows direct integration into roll-to-roll reel processes. A production-floor failure mode documented on a custom 4-station web coater (line speed 0.8 m min⁻¹) involves edge-current density amplification — auxiliary cathodes masked with 50 µm Kapton tape reduced thickness non-uniformity from ±25% to ±7%. Device qualification for supercapacitor coin cells (CR2032) requires specific capacitance measured by cyclic voltammetry per IEC 62391-2 and equivalent series resistance via electrochemical impedance spectroscopy at 100 kHz.
End-use devices incorporating these electrodes include electrochromic smart windows requiring optical modulation of >40% at 600 nm and textile-based wearable energy storage, where bending-radius tolerance down to 3 mm is verified by 1000-cycle mandrel flex tests without exceeding a 20% capacitance loss. Electrodeposition of poly(N-methylpyrrole) onto cold-rolled low-carbon steel (EN 10130 DC01) grade substrates consistently suppresses under-film filiform corrosion propagation to ≤ 0.3 mm in ASTM B368 CASS tests after 96 hours, matching the performance of hexavalent chromium sealers without their REACH Annex XIV authorization requirements. The electrolytic bath is prepared by dissolving N-methylpyrrole at 0.2 M and sodium salicylate as supporting electrolyte at 0.1 M in deionized water, adjusted to pH 3.0 with phosphoric acid; deposition proceeds in a pulse potentiostatic mode with 1.2 V (vs. Ag/AgCl) on-time for 10 s and 0 V off-time for 2 s, accumulating a 15–20 µm thick film in 30 cycles. Post-rinse cross-hatch adhesion measured by ISO 2409:2020 yields class 0 only when the steel surface has been pretreated with a silane coupling agent (γ‑glycidoxypropyltrimethoxysilane) at 2 vol% hydrolysis. A documented processing bottleneck on pilot coil-coating lines is anode-shield design; without forced electrolyte flow, monomer depletion at the diffusion layer collapses deposition efficiency by 40% beyond a belt speed of 5 m min⁻¹. The finished coated sheet is used for appliance cabinet back panels and engine-compartment brackets, where a service temperature variance of −40 to 120°C does not induce microcracking detectable by impedance spectroscopy below 10⁶ Ω cm² at 0.01 Hz (per ISO 16773-2). Photocurable Donor-Acceptor Complexes Modify Ink-Jet Rheology and Adhesion ProfilesFormulation of oxygen-insensitive UV-curable inks exploits the electron-rich character of N-methylpyrrole, which forms a ground-state charge-transfer complex with triacrylate acceptors such as trimethylolpropane triacrylate (TMPTA). This donor-acceptor pair initiates radical polymerization under 395 nm LED irradiation at 8 W cm⁻² without the addition of a conventional Type I or Type II photoinitiator, thereby eliminating benzophenone migration issues that restrict food-packaging compliance under EU 10/2011 and Swiss Ordinance 817.023.21. An optimal donor:acceptor molar ratio of 1:1 yields a real-time FTIR conversion of 84% (peak area at 810 cm⁻¹) and a gel content of 78% after 3 passes under an LED array. Bulk viscosity at jetting temperature (50°C) must remain below 12 mPa·s for piezo printhead compatibility (Xaar 1003, nozzle diameter 35 µm); excessive N-methylpyrrole loading above 1:0.8 ratio causes jetting deviations exceeding ±3 mil positional accuracy on corrugated substrates. Pre-cure tack and final cross-hatch adhesion (rated 4B on corona-treated BOPP per ASTM D3359) are systematically recorded.
A tightly constrained pot-life limitation governs line-side logistics: the N-methylpyrrole/TMPTA mixture exhibits a 40% viscosity increase after 8 hours at ambient temperature (25°C) due to spontaneous thermal oligomerization, necessitating inline degassing and a sealed, nitrogen-blanketed reservoir. The resulting prints serve as tactile warning symbols on thermoformed blisters and beverage sleeve labels that must withstand hot-fill (85°C) and ice-water quenching without interlayer delamination. |
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The heterocyclic building block N-methylpyrrole (CAS 96-54-8, empirical formula C₅H₇N) functions as a methylated pyrrole derivative with a molecular weight of 81.12 g/mol. The liquid exhibits a boiling point of 112–113 °C at 101.3 kPa, a density of 0.915 g/mL at 20 °C, and a flash point of 15 °C (closed cup, ASTM D56-22), classifying it as a highly flammable liquid under UN 1993. Disruption of N–H···π hydrogen bonding by the methyl group lowers the boiling point by approximately 17 °C relative to unsubstituted pyrrole and reduces dynamic viscosity to 0.79 mPa·s at 25 °C. Commercial supply chains offer the product in synthesis-grade (≥98%) and electronic-grade (≥99.5%) packages, the latter subjected to double fractionation over calcium hydride to depress sodium and potassium concentrations below 1 ppm. Applications span electropolymerization of conductive polymer films, regiospecific 2-acylation for pharmaceutical intermediates, vapor deposition of nitrogen-doped carbon layers, and Lewis base catalysis in organometallic cross-couplings. The following table summarizes routinely available specification tiers across the supply base.
| Parameter | Industrial/Technical Grade | Synthesis Grade | Electronic/Optical Grade | Test Method |
|---|---|---|---|---|
| Purity (GC) | ≥98.0% | ≥99.0% | ≥99.5% | GC-FID, area normalization |
| Water content | ≤0.10% | ≤0.05% | ≤0.01% | ASTM E203-16 |
| Color (APHA) | ≤100 | ≤50 | ≤10 | ASTM D1209-05(2019) |
| Chloride (IC) | ≤50 ppm | ≤10 ppm | ≤1 ppm | EPA 300.1 |
| Heavy metals (ICP-OES) | — | ≤5 ppm | ≤1 ppm | USP 〈233〉 |
| Residual pyrrole | <0.5% | <0.1% | <0.01% | GC-MS, SIM mode |
The electron-donating methyl substituent raises the highest occupied molecular orbital (HOMO) energy by approximately 0.3 eV, shifting the anodic oxidation peak potential from +0.8 V vs. SCE for pyrrole to +1.1 V vs. SCE for N-methylpyrrole in acetonitrile containing 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF₆). This expanded potential window necessitates non-aqueous electrolytes with sufficient electrochemical stability; propylene carbonate and acetonitrile are selected, whereas aqueous electrolytes induce premature overoxidation at the pendant methyl site. Potentiostatic deposition onto indium tin oxide (ITO)-coated glass at +1.2 V (three-electrode configuration, Pt counter electrode) yields adherent poly(N-methylpyrrole) films whose thickness, controlled by the passed charge, ranges from 0.5 µm to 5 µm. Film conductivity, determined in accordance with ASTM D4496-21 using a four-point probe, typically falls in the 10⁻² S/cm to 10 S/cm interval depending on the doping anion; perchlorate-doped films exhibit values at the upper end, whereas bulky para-toluenesulfonate counterions depress conductivity by a factor of 10–100. By comparison, polypyrrole films prepared under identical conditions routinely achieve conductivities of 1–100 S/cm, attributable to a more planar chain conformation unhindered by the N-methyl group. SEM micrographs reveal globular aggregates of 200–500 nm diameter for poly(N-methylpyrrole), contrasting with the cauliflower morphology of polypyrrole. X-ray diffractograms show a broad amorphous halo centered at 2θ ≈ 25°, confirming reduced long-range order. This difference becomes a processing advantage: poly(N-methylpyrrole) exhibits measurable solubility in N-methyl-2-pyrrolidone (NMP) and dimethyl sulfoxide (DMSO) up to 5 mg/mL, enabling slot-die coating of conductive interlayers—a route inaccessible to insoluble polypyrrole without derivatization. On pilot-scale continuous electrodeposition lines using a roll-to-roll ITO web 300 mm wide, local current-density non-uniformity causes edge-thickening; integration of interdigitated auxiliary cathode frames reduces thickness variation across the web to ±7%. In-line multi-wavelength ellipsometry verifies thickness during winding at speeds up to 0.5 m/min. Post-deposition dedoping in 0.1 M aqueous NH₄OH for 30 min lowers conductivity by an order of magnitude but raises the onset of thermal de-doping degradation to 250 °C under nitrogen as measured by thermogravimetric analysis (TGA). Overoxidation must be strictly avoided: stepping the potential beyond +1.3 V results in an irreversible increase in charge-transfer resistance (Rct) by more than 300%, identifiable via electrochemical impedance spectroscopy (EIS) at 10 mHz–100 kHz and accompanied by film delamination.
In the synthesis of the non-steroidal anti-inflammatory drug ketorolac tromethamine, N-methylpyrrole serves as the precursor for 2-acetyl-N-methylpyrrole via a Friedel-Crafts acetylation using acetyl chloride and anhydrous aluminum chloride in dichloromethane. The N-methyl substituent enforces exclusive 2-position substitution; unsubstituted pyrrole under analogous conditions generates 3–5% of the 3-acetyl isomer, which complicates purification and reduces overall yield. The exothermic addition of acetyl chloride is executed at a jacket-controlled temperature of –5 °C to 0 °C on a 50 kg scale, with a dosing rate of 0.4–0.6 L/h to maintain the internal temperature below 5 °C. In-process monitoring by HPLC (C18 column, 254 nm UV detection) requires residual N-methylpyrrole to fall below 0.5% area before the mixture is quenched into chilled 2 M HCl. The crude 2-acetyl-N-methylpyrrole is isolated by fractional distillation at 15 mmHg; the main cut distills at 90–92 °C with a purity exceeding 99.5% by GC. In continuous-flow reactor configurations, a residence time of 8 min in a 1.0 mm ID PFA coil at 0 °C achieves 98% conversion, with ReactIR monitoring of the 1805 cm⁻¹ acetyl carbonyl band providing real-time endpoint detection. Trace N-ethylpyrrole impurity introduced from a different supplier lot led to over-alkylation byproducts detected at 0.15–0.2% in early campaigns; control of the starting-material pyrrole content below 0.1% (as shown in the specification table) eliminated this failure mode. Subsequent conversion of the acetyl intermediate to ketorolac follows the route disclosed in USP Ketorolac Tromethamine RS and is beyond the scope of the present discussion.For vapor deposition of nitrogen-doped graphene and fabrication of hole-transport layers in organic light-emitting diodes (OLEDs), metallic contaminants quench electroluminescence. Suppliers therefore deliver electronic-grade N-methylpyrrole in borosilicate glass ampoules fused under argon with an internal moisture specification of ≤0.01% (Karl Fischer). Trace-metal screening by glow-discharge mass spectrometry (GDMS) certifies sodium, potassium, and iron each below 1 ppm. Ampoule transfer into process gloveboxes (O₂ < 0.1 ppm, H₂O < 0.1 ppm) is performed through PTFE-lined septum ports, and the material is pre-dried over activated 3A molecular sieves that have been calcined at 300 °C under vacuum for 24 h. N-methylpyrrole’s boiling point of 112 °C permits trap-to-trap purification on a Schlenk manifold without contamination by higher oligomers, an advantage over N-ethylpyrrole, which boils at 128–130 °C and tends to retain dimeric species that manifest as ghost peaks in TGA of the final film. In an OELD stack, injection of the monomer from a temperature-controlled bubbler at 30 °C with a carrier gas flow of 50 sccm argon into a 800 °C CVD furnace yields N-doped graphene with nitrogen atomic percentages of 2–5% as quantified by X-ray photoelectron spectroscopy (XPS). Film sheet resistance on 300 nm SiO₂/Si substrates falls between 500 Ω/sq and 2 kΩ/sq depending on growth time. The removal of the methyl group during pyrolysis distinguishes the precursor from unsubstituted pyrrole, which yields higher residual nitrogen content but also introduces more lattice defects. Handling failures during ampoule opening—exposure to ambient air beyond 30 s—result in moisture uptake exceeding 50 ppm, elevating pinhole densities in spin-coated films beyond the threshold specified in SEMI S2 guidelines for flat-panel display manufacturing.
| Property | N-Methylpyrrole | Pyrrole | N-Ethylpyrrole | Reference Method |
|---|---|---|---|---|
| Boiling point (101.3 kPa) | 112–113 °C | 129–131 °C | 128–130 °C | ASTM D86-23 |
| Flash point (closed cup) | 15 °C | 39 °C | 28 °C | ASTM D56-22 |
| Dynamic viscosity (25 °C) | 0.79 mPa·s | 1.22 mPa·s | 0.91 mPa·s | ASTM D7042-21a |
| Electropolymerization onset potential | +1.1 V vs. SCE | +0.8 V vs. SCE | +1.0 V vs. SCE | Cyclic voltammetry, 0.1 M TBAPF₆/CH₃CN |
| Typical polymer conductivity | 10⁻²–10 S/cm | 1–100 S/cm | 10⁻³–1 S/cm | Four-point probe, ASTM D4496-21 |
| 2-Acetylation regiospecificity | > 99% at 2-position | 95–97% at 2-position | > 99% at 2-position | HPLC, NMR |
