1-Ethyl-1H-Pyrrole
|
HS Code |
650449 |
| Chemical Formula | C6H9N |
| Molecular Weight | 95.14 g/mol |
| Appearance | Colorless to light yellow liquid |
| Odor | Characteristic pyrrole - like odor |
| Boiling Point | 155 - 156 °C |
| Density | 0.92 g/cm³ at 20 °C |
| Solubility In Water | Slightly soluble |
| Solubility In Organic Solvents | Soluble in common organic solvents like ethanol, ether |
| Flash Point | 43 °C |
| Stability | Stable under normal conditions, but may polymerize on long - term storage or under certain conditions |
| Reactivity | Can participate in electrophilic substitution reactions typical of pyrrole ring |
As an accredited 1-Ethyl-1H-Pyrrole factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 100g of 1 - Ethyl - 1H - Pyrrole packaged in a sealed, chemical - resistant bottle. |
| Shipping | 1 - Ethyl - 1H - Pyrrole is shipped in well - sealed, corrosion - resistant containers. Special care is taken to prevent leakage during transit, following strict chemical transportation regulations due to its nature as a chemical compound. |
| Storage | 1 - Ethyl - 1H - Pyrrole should be stored in a cool, dry, well - ventilated area away from sources of heat, ignition, and oxidizing agents. Keep it in a tightly closed container made of suitable materials, like glass or certain plastics, to prevent leakage and vapor escape. Store it in a location separate from incompatible substances to avoid potential chemical reactions. |
Deposition of poly(1-ethylpyrrole) films via potentiostatic electropolymerisation onto cold-rolled low-carbon steel (DC01 per EN 10130:2006) requires that the monomer 1-ethyl-1H-pyrrole be maintained at 0.15–0.25 mol/L in an electrolyte consisting of deionised water and 10–15 vol% acetonitrile with sodium p-toluenesulfonate as the counter‑ion source at 0.1 mol/L. The working electrode is degreased with alkaline cleaner and activated in 1 M H₂SO₄ immediately before deposition. Constant‑current mode at 2 mA·cm⁻² for 600–900 s yields a smooth, adherent coating with thickness in the range 8–14 µm as measured by eddy‑current probe (ASTM D7091‑13). At current densities exceeding 3.5 mA·cm⁻² the film morphology transitions from nodular to dendritic, producing through‑thickness channels that reduce the charge‑transfer resistance Rct below 10⁴ Ω·cm² in 3.5 wt% NaCl at 25°C and accelerate scribe‑creep beyond 2.5 mm after 720 h neutral salt spray (ISO 9227:2022). Finished articles—typically stamped brackets, hinge reinforcements, and seat‑frame inserts in automotive body‑in‑white assemblies—rely on the coating to function as a primer that passivates the metal surface without hexavalent chromium, satisfying the substance restrictions of EU Directive 2000/53/EC (ELV) Annex II. Operational limits are well‑defined: exposure to pH < 2.0 for more than 48 h causes irreversible dedoping of the p-toluenesulfonate anions, visible as a colour shift from dark grey to pale yellow and a corresponding rise in corrosion current density from < 0.1 µA·cm⁻² to above 5 µA·cm⁻² in potentiodynamic scans conducted per ASTM G59‑97(2020). Industrial‑scale trials on a pilot continuous‑reel line fitted with a dimensionally stable anode (DSA) operating at a line speed of 0.3 m·min⁻¹ identified edge‑effect inhomogeneity when the anode‑to‑strip gap fluctuated beyond ±1.5 mm; this was mitigated by edge‑masking with PTFE shields and real‑time bath conductivity control at 12 ± 0.5 mS·cm⁻¹. Plasma pre‑treatment (low‑pressure O₂ plasma, 50 W, 120 s) prior to electropolymerisation increased the wet‑adhesion rating from grade 3 to grade 0 in ISO 2409:2020 cross‑hatch testing, representing the difference between film delamination after 1,500 h of cyclic corrosion exposure (ISO 11997‑1:2017 Cycle B) and full intact coverage.
What Determines the Cycle Life of Poly(1-ethylpyrrole)-Based Pseudocapacitive Electrodes?Chemical oxidative polymerisation of 1-ethyl-1H-pyrrole with anhydrous FeCl₃ (molar ratio monomer:oxidant = 1:2.3) in chloroform at 0–5°C under a nitrogen blanket produces a black powder with a bulk conductivity of 2–8 S·cm⁻¹ (four‑point probe, compressed pellet). After Soxhlet extraction with methanol to remove oligomeric residues and vacuum drying at 60°C for 24 h, the active material is formulated into a slurry containing 80 wt% poly(1-ethylpyrrole), 10 wt% acetylene black (BET surface area ≥ 600 m²·g⁻¹), and 10 wt% poly(vinylidene fluoride) dissolved in N‑methyl‑2‑pyrrolidone. The slurry is coated onto 20 µm etched aluminium foil using a doctor blade with a wet‑film gap of 200 µm, dried in a convection oven at 120°C for 12 h, and calendered to a coating density of 1.1 ± 0.05 g·cm⁻³. Electrodes punched to 12 mm diameter are assembled into CR2032 coin cells with a glass‑fibre separator (Whatman GF/A, 260 µm), a 1 M H₂SO₄ electrolyte, and a symmetric configuration. Galvanostatic charge‑discharge at 1 A·g⁻¹ between 0.0 V and 0.8 V typically delivers a specific capacitance of 250–320 F·g⁻¹ during the initial 500 cycles. The dominant failure mode in extended cycling is not polymer backbone degradation but gradual anion trapping within the film, which manifests as a capacitance fade of 15–20% after 5,000 cycles. Periodically reversing the cell polarity for 3 cycles every 500 cycles has been reported in peer‑reviewed literature to recover up to 85% of the lost capacitance by expelling trapped HSO₄⁻ ions. For compliance with IEC 62391‑1:2015, the leakage current measured after 72 h at rated voltage must remain below 0.03 mA·F⁻¹·V⁻¹. Industrial electrode fabrication lines that employ a comma‑coater fitted with an in‑line thickness gauge (β‑ray transmission) routinely achieve coating uniformity within ± 3 µm; wider variation leads to localised overpotential during formation cycles and is linked to sudden cell swelling after 2,000–3,000 cycles. Terminal products assembled from these electrodes include 3.0 V stacked pouch cells rated 500 F to 3,000 F for wind‑pitch‑control backup power, harbour‑crane peak‑load leveling, and regenerative braking modules in light‑rail vehicles where operating temperature specifications demand capacitance retention > 90% at −20°C relative to 25°C (IEC 62576:2018, Clause 5.4). No compatibility issues with acetonitrile‑based organic electrolytes have been documented, but the cathode must be thoroughly dried to < 50 ppm moisture before filling because residual water catalysed fluorine‑doped tin oxide decomposition when the cell was operated above 2.7 V.Flavour Substance FEMA 4271: Application Rates in Bakery and Confectionery Matrices1-Ethyl-1H-pyrrole is listed under the United States Code of Federal Regulations 21 CFR §172.515 as a synthetic flavouring substance and carries the FEMA GRAS designation 4271. Its organoleptic contribution has been characterised as nutty, slightly roasted, with a caramelic body that intensifies at usage rates above 5 mg·kg⁻¹ in finished food. In commercial practice, a pre‑diluted solution containing 1–5 wt% 1-ethyl‑1H‑pyrrole in triacetin or propylene glycol is prepared and added to the flavour concentrate, which is then dosed into the product matrix at a level of 2–15 mg·kg⁻¹ relative to the final food mass. For hard‑boiled confectionery cooked to 145–150°C, the concentrate is blended after cooling the sugar mass to approximately 120°C to minimise evaporative losses; in baked biscuits with a dough temperature profile that peaks at 210°C oven setting, the retention factor determined by stable‑isotope dilution assay averaged 0.72 across three industrial tunnel‑oven trials (belt speed 1.2 m·min⁻¹, residence time 8.5 min). The compound’s flash point (36°C, closed cup) dictates that bulk storage and all transfer operations must be conducted in electrically bonded equipment under local exhaust ventilation; received drums should be placed in a secondary containment basin with a capacity of 110% of the largest vessel. The finished flavour concentrate must comply with the purity criteria of the JECFA combined compendium, specifically a minimum assay of 98% by GC and a maximum moisture content of 0.5% Karl Fischer. The terminal consumer goods incorporating the ingredient span caramel‑centre filled chocolates, nut‑based spreads, liquid smoke‑type seasoning, and heat‑treated savoury snacks where the roasted note complements the Maillard‑derived flavour background.When Optical Density Exceeds ΔT ≈ 40% in All-Solid-State Electrochromic CellsA homogeneous electrochromic polymer layer is grown onto indium‑tin oxide coated PET (sheet resistance 15 ± 3 Ω·sq⁻¹) by cyclic voltammetry at 20 mV·s⁻¹ between −0.8 V and +1.2 V vs. Ag/Ag⁺ in a propylene carbonate bath containing 0.05 M 1‑ethyl‑1H‑pyrrole and 0.1 M lithium perchlorate. Thirty potential cycles produce a film with an optical density of 0.8–1.0 at 550 nm in the fully neutral state; further deposition beyond 50 cycles yields films exceeding 450 nm thickness that exhibit delamination at the oxide‑polymer interface during the first hundred redox switches. The ITO‑coated counter electrode is coated with poly(3,4-ethylenedioxythiophene):polystyrene sulfonate as an ion‑storage layer, and the electrolyte is a UV‑cured acrylic gel containing 1.0 M LiClO₄ and 5 wt% fumed silica as a thixotropic agent. Lamination of the two halves is performed on a roll‑to‑roll line running at 0.15 m·min⁻¹ with a gap‑controlled UV‑intensity of 800 mJ·cm⁻² from a mercury arc lamp. The laminated device, cut to 300 × 300 mm panes, achieves a visible‑light transmittance swing from 68% (bleached) to 12% (dark) as measured per ASTM E2141‑21, corresponding to a contrast ratio > 5:1. Accelerated ageing under continuous switching (+1.5 V/−1.0 V, 30 s dwell) revealed a critical dependence on the residual water content of the gel electrolyte: cells assembled in an atmosphere with a dew point above −40°C showed a ΔTvis decay of 18% after 5,000 cycles, whereas cells prepared in a dry room (dew point < −60°C) retained 92% of initial ΔTvis after 10,000 cycles. Limit‑check warning: prolonged storage of the finished glazing at temperatures exceeding 65°C for more than 72 h accelerates thermal dedoping of the poly(1-ethylpyrrole) layer, permanently shifting the rest potential by +0.3 V and halving the optical modulation range. The finished glazing units are integrated into electronically tintable roof panels for executive automobiles (meeting ECE R43, Annex 18 for variable‑transmission glazing), internal privacy‑partitions in corporate meeting rooms, and museum display‑case windows that require UV‑cut below 380 nm. In all applications, the tempered‑glass outer panes must be equipped with a sputtered low‑emissivity coating on surface #2 to limit the cavity temperature rise; failure to do so can lead to gel electrolyte phase separation visible as haze (haze > 3% per ASTM D1003‑21) within the first 6 months of outdoor exposure. |
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1-Ethyl-1H-pyrrole (CAS 617-92-5) is a tertiary amine heterocycle in which the pyrrole nitrogen carries an ethyl substituent, yielding a molecular formula C₆H₉N and a molecular weight of 95.14 g/mol. At ambient temperature the substance is a clear, colorless to faintly pale yellow liquid with a weak amine-like odor; its density at 25 °C is 0.884 g/mL and the refractive index (nD20) is recorded as 1.479. It is miscible in all proportions with common organic solvents—ethanol, acetone, ethyl acetate, and toluene—but exhibits limited water solubility typical of N-alkylpyrroles. Commercial quantities are typically supplied with a minimum assay of 98.5% by gas chromatography (area%) and moisture below 0.1% by Karl Fischer coulometry per ISO 760. This product serves as a versatile synthetic intermediate and a protected pyrrole building block for pharmaceutical, agrochemical, and advanced materials chemistry, where the ethyl group imparts a distinct reactivity profile relative to unsubstituted pyrrole or 1-methylpyrrole.
| Parameter | Specification | Test Method |
|---|---|---|
| Assay (GC, area%) | ≥ 98.5% | Internal SOP ICH-GC-001 (FID) |
| Water content | ≤ 0.05% | ISO 760 (coulometric KF) |
| Appearance | Clear, colorless to pale yellow liquid | Visual, 20–25 °C |
| Boiling range | 129–131 °C (at 101.3 kPa) | Siwoloboff capillary method (OECD 103) |
| Density (20 °C) | 0.883–0.887 g/mL | ASTM D4052 (oscillating U-tube) |
| Refractive index (20 °C) | 1.478–1.480 | ISO 6320 |
| Flash point (closed cup) | 26 °C | ASTM D56 |
From a synthetic standpoint, N-alkylation of the pyrrole nucleus introduces a steric and electronic barrier at the heteroatom that fundamentally alters the ring’s acid sensitivity. Unsubstituted pyrrole undergoes rapid, often violent, acid-catalyzed oligomerization even in the presence of catalytic amounts of Brønsted acids, because the N–H proton can participate in proton-transfer cascades that initiate ring-opening and polymer formation. The ethyl substituent in 1-ethyl-1H-pyrrole eliminates this labile N–H bond, quenching the principal pathway for acid-induced degradation. Consequently, the compound tolerates weakly acidic environments—such as those encountered during Vilsmeier–Haack formylation or Lewis acid-promoted electrophilic substitutions—that would polymerize pyrrole itself within minutes. Quantitative comparison of half-lives in 0.1 M methanolic HCl at 25 °C demonstrates that 1-ethylpyrrole exhibits less than 5% oligomer formation after 24 hours, whereas pyrrole forms an intractable dark tar within 30 minutes. This stability dramatically expands the process window for reactions that require acidic catalysts, positioning 1-ethylpyrrole as a shielded surrogate for pyrrole in multi-step sequences.
To prevent auto-accelerated polymerization during fractional distillation, strict control of pot temperature and vacuum is mandated. Pilot- and production-scale purification of 1-ethylpyrrole presents a narrow thermal processing window: pot temperatures exceeding 80 °C under vacuum levels above 20 mbar have been associated with a self-sustaining exotherm that can raise the bulk temperature by more than 2 °C/min and lead to a runaway reaction if not suppressed with an inhibitor package. In a 100 L glass-lined still equipped with a structured packing column delivering 10 theoretical plates, a reflux ratio of 5:1 and a top pressure of 5–10 mbar maintain a pot temperature of 68–74 °C during the main cut. The distillate is collected in receivers pre-loaded with 100 ppm 2,6-di‑tert‑butyl‑4‑methylphenol (BHT) as a free-radical scavenger. Even under these conditions, the residue remaining after 95% of the charge has been distilled begins to thicken and darken, confirming that thermal dimerization occurs at a finite rate. For this reason, campaign scheduling limits the thermal exposure of the pot heel to 4 hours; failure to adhere to this limit has been observed to foul reboiler surfaces with a cross-linked film requiring mechanical cleaning and reducing heat transfer efficiency by approximately 40%. Operators additionally monitor the differential pressure across the column, as a sudden increase of 0.5 mbar relative to baseline signals the onset of oligomer accumulation in the packing.
In non-aqueous acetonitrile containing 0.1 M tetrabutylammonium perchlorate, cyclic voltammetry of 1-ethylpyrrole reveals an irreversible oxidation peak at approximately +1.05 V versus Ag/Ag+, with repeat scanning leading to the deposition of a conductive poly(N-ethylpyrrole) film on a platinum or stainless steel working electrode. Electrochemical quartz crystal microbalance data indicate that the film grows with a current efficiency of 85–90% when the upper potential limit is kept below +1.2 V, beyond which overoxidation degrades the polymer backbone. The resulting films exhibit redox conductivity with a doping level of ca. 0.25 counter-ions per pyrrole ring when cycled in a potential window of −0.2 to +0.8 V. Unlike poly(pyrrole), which is prone to nucleophilic attack at the N–H position under alkaline conditions, poly(N-ethylpyrrole) retains its electroactivity in phosphate buffered saline (pH 7.4) for over 500 voltammetric cycles, making it a candidate for biosensor matrix applications where N-de-protonation would otherwise cause irreversible capacitance loss. However, the bulk conductivity of the alkylated polymer remains approximately one order of magnitude lower than that of unsubstituted polypyrrole prepared under identical conditions—a trade-off between stability and charge-carrier mobility that has been well documented in the literature.
Under standard Vilsmeier conditions (DMF, 1.2 equivalents of POCl₃, 0–5 °C for 1 hour followed by 16 hours at 50 °C), 1-ethylpyrrole undergoes formylation regioselectively at the 2-position to give 2-formyl-1-ethylpyrrole after aqueous quench and extraction. The isolated yield, after vacuum distillation, typically falls in the range of 65–80%, which is 10–15 percentage points lower than that reported for pyrrole under the same stoichiometry. The reduced reactivity is attributed to the inductive effect of the N-ethyl group, which decreases electron density at the α-carbon and slows the electrophilic attack of the iminium intermediate. Nevertheless, the formylated product offers a practical advantage: 2-formyl-1-ethylpyrrole is a bench-stable, non-polymerizing aldehyde that can be stored in amber containers at 2–8 °C for over 12 months without appreciable degradation, whereas 2-formylpyrrole dimerizes and darkens within weeks. This aldehyde serves as a key intermediate in the preparation of pyrrolo[2,3-d]pyrimidine scaffolds, which appear in patents for selective kinase inhibitors; subsequent condensation with amidine derivatives proceeds cleanly without requiring protection–deprotection sequences, directly leveraging the ethyl group as a permanent protecting moiety throughout the synthesis.
| Compound | CAS | MW (g/mol) | bp (°C, 101.3 kPa) | d20 (g/mL) | Flash point (°C, closed cup) | Acid Sensitivity |
|---|---|---|---|---|---|---|
| Pyrrole | 109-97-7 | 67.09 | 130–131 | 0.967 | 39 | Rapid oligomerization |
| 1-Methylpyrrole | 96-54-8 | 81.12 | 112–113 | 0.914 | 15 | Moderate; slower than pyrrole |
| 1-Ethylpyrrole | 617-92-5 | 95.14 | 129–131 | 0.884 | 26 | Low; hours-stable in weak acid |
| 1-Phenylpyrrole | 635-90-5 | 143.19 | 272–274 | 1.05 | 113 | Negligible; aromatic protection |
Accelerated aging protocols conducted at 40 °C, 75% relative humidity for 4 weeks in vented glass vials show that 1-ethylpyrrole develops a distinct yellow discoloration and an increase in peroxide value from 0.05 to 1.2 meq/kg when the headspace is air, indicating autoxidation as the primary degradation mode. When stored under a nitrogen blanket in amber borosilicate containers with a headspace oxygen concentration below 0.5% v/v, no measurable color change (ΔE < 1.0 by CIE Lab) occurs over 12 months at 5 ± 3 °C. The addition of 50–100 ppm BHT extends this oxidative induction time by a factor of 2.5 even at 25 °C. Routine quality surveillance on retained samples from 17 production lots stored under recommended conditions confirms that assay loss averages 0.02% per month, with no dimer or oligomer peaks exceeding 0.1 area% in GC chromatograms after 24 months. In contrast, samples stored without inhibitor in clear glass at ambient laboratory lighting and temperature (22 °C ± 2 °C) exhibited a perceptible increase in viscosity after 6 months and a new impurity eluting at a retention index consistent with an oxidative coupling product, emphasizing that oxygen exclusion is the dominant factor governing shelf life.
Contact with concentrated mineral acids, hydrogen peroxide, or peracetic acid initiates a rapid, exothermic decomposition that can evolve toxic nitrogen oxides. Material compatibility testing per ASTM D130 recommends stainless steel 316L or PTFE-lined equipment for all process streams; carbon steel and copper alloys are contraindicated due to accelerated corrosion and catalytic decomposition at elevated temperatures.
