1H-Pyrrole-2-Carbaldehyde
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HS Code |
909182 |
| Name | 1H-Pyrrole-2-Carbaldehyde |
| Molecular Formula | C5H5NO |
| Molar Mass | 95.10 g/mol |
| Appearance | Yellow to brown solid or liquid |
| Boiling Point | 215 - 216 °C |
| Melting Point | 14 - 16 °C |
| Density | 1.15 g/cm³ |
| Solubility | Soluble in organic solvents like ethanol, diethyl ether |
| Flash Point | 93 °C |
| Refractive Index | 1.593 |
| Pka | 13.6 |
As an accredited 1H-Pyrrole-2-Carbaldehyde factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 100g of 1H - Pyrrole - 2 - Carbaldehyde packaged in a sealed, airtight container. |
| Shipping | 1H - Pyrrole - 2 - Carbaldehyde, a chemical, is shipped with strict safety protocols. Packed in air - tight, corrosion - resistant containers, it's transported via approved carriers, ensuring compliance with chemical shipping regulations for safe delivery. |
| Storage | 1H - Pyrrole - 2 - Carbaldehyde should be stored in a cool, dry place away from heat and ignition sources. It is advisable to keep it in a tightly sealed container to prevent exposure to air and moisture, which could potentially lead to degradation. Store it separately from oxidizing agents and incompatible substances. Ideal storage conditions help maintain its chemical integrity and safety. |
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In the formulation of heat-stable nutty topnotes for instant coffee and extruded snacks, pyrrole-2-carboxaldehyde is incorporated at 0.05–0.20 wt% of the compounded liquid flavor, translating to a final food concentration of 1–20 ppm depending on the matrix. Regulatory compliance for this application is governed by FEMA GRAS No. 3714, its listing in 21 CFR 172.515 as a synthetic flavoring substance, and JECFA No. 1714. Industrial compounding proceeds by pre-dissolving the neat aldehyde in propylene glycol (BP/USP grade) at 25–30°C using a Silverson L5M-A high-shear rotor/stator mixer operating at 5,000 rpm for 15 min; the solution is then blended into the base flavor emulsion and homogenized. When a shelf-stable encapsulated powder is required, the liquid flavor is spray-dried onto a maltodextrin carrier (DE 10–12) using a Niro Mobile Minor™ spray dryer with an inlet temperature of 180°C and outlet of 90°C, yielding a free-flowing powder with a final moisture content below 4.0%. The finished product—a water-soluble encapsulated pyrrole-2-carboxaldehyde flavor—is utilised in instant coffee sachets, bakery premixes, and confectionery fillings. How Does Monomer Feed Ratio Influence Q-Band Absorption in Pyrrole-Appended Porphyrins?Syntheses conducted under ICH Q7 active pharmaceutical ingredient intermediate controls employ a Lindsey-type condensation in which pyrrole-2-carboxaldehyde constitutes between 25 mol% and 100 mol% of the total aldehyde monomer feed. A typical batch in a 500 L Pfaudler glass-lined reactor inertised with nitrogen charges freshly distilled pyrrole (1.0 eq), pyrrole-2-carboxaldehyde (0.25–1.0 eq), and a non-pyrrolic aldehyde such as benzaldehyde (0.75–0.0 eq) in anhydrous dichloromethane (12 L per mole of total aldehyde). After cooling to −5 ± 2°C, boron trifluoride diethyl etherate (0.1 eq) is added dropwise under agitation at 80 rpm, and the mixture is allowed to warm to 20°C over 18 h. The resulting porphyrinogen is oxidised in situ with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) (1.2 eq) at 25°C for 2 h. Purification proceeds over a Teledyne Isco CombiFlash Rf+ automated chromatography system equipped with a 330 g RediSep silica column, using a heptane/ethyl acetate gradient, and the fraction containing the target porphyrin is evaporated on a Büchi Rotavapor R-220 at 40°C / 8 mbar. The dry product—a statistical mixture enriched in 5,10,15,20-tetra(pyrrol-2-yl)porphyrin—is then re-dissolved in DMF and lyophilised. The final porphyrin is supplied as a GMP-compliant photosensitiser intermediate for light-activated antimicrobial coatings and experimental photodynamic therapy formulations governed by USP <1040> requirements for laser safety and dosimetry validation. When BODIPY FL-Carboxylic Acid Is Synthesised via Acid-Catalysed CondensationThe production of BODIPY FL succinimidyl ester—a widely used amine-reactive fluorescent probe for antibody labelling in flow cytometry—requires pyrrole-2-carboxaldehyde in a discrete first-stage condensation with 2,4-dimethylpyrrole at a strict 1.0:1.0 molar ratio. The reaction is carried out under ISO 13485:2016 quality management when the product is destined for in-vitro diagnostic device components. In a 20 L jacketed glass vessel, dichloromethane (10 L) is charged, followed by the two pyrrolic monomers, and the mixture is sparged with argon for 30 min. Trifluoroacetic acid (0.1 eq) is introduced, and the condensation proceeds at 22 ± 1°C for 4 h, forming the dipyrromethane intermediate. After sequential addition of DDQ (1.1 eq) and BF₃·OEt₂ (3.0 eq relative to dipyrromethane) at 0°C, the mixture is neutralised with N,N-diisopropylethylamine (6.0 eq) and allowed to reach 25°C over 1 h. Purification involves two silica-gel chromatographic passes (CombiFlash NextGen 300, gradient 0–10% ethyl acetate in hexane) to achieve a purity greater than 99.0% (HPLC, λ = 254 nm). The final carboxaldehyde-derived BODIPY acid is converted to the NHS ester with N,N′-disuccinimidyl carbonate yielding an activated fluorophore typically incorporated at 10–50 µg per 10⁶ cells for flow cytometry panels, meeting spectral requirements of excitation/emission 502/510 nm. Electrochemical Copolymerisation of Pyrrole and Pyrrole-2-Carboxaldehyde in Quaternary Ammonium ElectrolytesAnti-static transparent electrode coatings on polyethylene terephthalate (PET) substrates are fabricated via potentiostatic copolymerisation from an acetonitrile solution containing 0.1 M pyrrole, 0.005–0.015 M pyrrole-2-carboxaldehyde (i.e., 5–15 mol% co-monomer), and 0.1 M tetraethylammonium tetrafluoroborate as supporting electrolyte. Compliance with IEC 61340-5-1 for electrostatic discharge protection mandates surface resistivity below 10¹¹ Ω/sq. A three-electrode cell fitted with an ITO-coated PET working electrode (10 × 10 cm², sheet resistance 60 Ω/sq), a platinum mesh counter electrode, and an Ag/AgCl (3 M KCl) reference electrode is operated using a Princeton Applied Research Parstat 4000 potentiostat in chronoamperometric mode at a constant potential of +1.20 V vs Ag/AgCl. The deposition time is controlled to achieve a film thickness of 300 ± 20 nm, as verified by profilometry (KLA Tencor P-7). After deposition, films are rinsed with acetonitrile and dried under a nitrogen stream at 60°C for 2 h. The resulting copolymer layer—poly(pyrrole-co-pyrrole-2-carboxaldehyde)—shows a static decay time of <0.01 s when measured per IEC 61340-2-3 and is incorporated into display packaging trays and electronic component carrier tapes. Schiff Base Derivatisation with Thiosemicarbazide and the Inhibition of Hydrogen Evolution on A36 SteelTo suppress metal weight loss during 15 wt% hydrochloric acid pickling of carbon steel components, a condensation product formed from pyrrole-2-carboxaldehyde and thiosemicarbazide is dosed at 0.2–1.0 wt% directly into the pickling bath at 60°C. The parent aldehyde is first converted to the Schiff base by reacting pyrrole-2-carboxaldehyde (1.0 mol) with thiosemicarbazide (1.05 mol) in hot ethanol (80°C, 2 h), followed by filtration and drying. The inhibitor is qualified by gravimetric immersion tests following NACE TM0169-2012 using ASTM A36 steel coupons (surface finish 120-grit, degreased with acetone). Triplicate coupons are immersed for 6 h in the inhibited acid; corrosion rates calculated from weight loss are required to be below 5.0 mm·yr⁻¹, and the inhibitor efficiency compared with a blank run typically exceeds 94%. The pre-synthesised Schiff base is supplied as a concentrated additive package to toll-blending companies where it is combined with propargyl alcohol and surfactants for use in continuous-strip pickling lines. The product falls under REACH registration obligations for corrosion inhibitors in industrial treatment fluids and must not be combined with strong oxidising agents at elevated temperatures to avoid decomposition of the thiosemicarbazone moiety. Conversion of the 2-formyl group to a nitrile remains the key transformation in the manufacture of fludioxonil, a phenylpyrrole fungicide registered under FAO specification 587/TC and EPA reg. no. 100-1263. Pyrrole-2-carboxaldehyde is charged into a 500 L glass-lined reactor containing demineralised water (200 L), and the mixture is cooled to 0–5°C. Hydroxylamine hydrochloride (1.05 eq) is added in portions while maintaining the temperature below 10°C, followed by stirring for 4 h to complete oxime formation. The intermediate oxime slurry is then treated with acetic anhydride (1.25 eq) at a controlled rate to keep the exotherm below 50°C, and dehydration proceeds under reflux at 118–122°C for 3 h. After distilling off by-product acetic acid, the crude 3-cyanopyrrole is extracted with ethyl acetate, washed with water, and crystallised from ethyl acetate/hexane (1:3 v/v) at 0°C, yielding a white crystalline solid with ≥98.5% GC purity. This intermediate is subsequently elaborated through dibromination and Suzuki coupling to furnish fludioxonil technical concentrate. Production facilities must adhere to GB/T 29380-2012 for fludioxonil technical material and comply with Chinese pesticide registration residuals monitoring (GB 2763 maximum residue limits in crops).
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1H-Pyrrole-2-carbaldehyde (CAS 1003-29-8), designated systematically as 2‑formylpyrrole, exhibits a molecular weight of 95.10 g·mol⁻¹ and a boiling point of 217–219°C at atmospheric pressure, with decomposition onset detectable at 220°C in air. Commercial bulk specifications for synthetic‑grade material require a gas‑chromatographic purity of ≥98.0% (ASTM E682), a water content of ≤0.2% w/w by Karl Fischer titration (ASTM E203), and a Hazen colour value below 100 (ASTM D1209). Assay by non‑aqueous oximation with O‑methylhydroxylamine hydrochloride (ASTM E222) generally agrees within ±0.5% of the GC value. Residual solvents are controlled per ICH Q3C: acetonitrile ≤410 ppm, dichloromethane ≤600 ppm. The neat liquid displays a density of 1.142 g·mL⁻¹ at 25°C and a refractive index nD20 between 1.5310 and 1.5330. To suppress autoxidation to pyrrole‑2‑carboxylic acid the product is routinely stabilised with 0.05–0.1 wt% butylated hydroxytoluene (BHT) and packaged under a nitrogen headspace in amber glass or fluorinated HDPE containers. Storage at 2–8°C with exclusion of UV radiation is mandatory; drummed quantities exceeding 100 L are handled in ISO‑tank containers equipped with nitrogen blankets and light‑excluding jackets.
| Impurity | Retention Index | Specification Limit | Observed Range (n = 12) |
|---|---|---|---|
| 2‑Methylpyrrole | 1085 | ≤0.5% | 0.08–0.35% |
| Pyrrole‑2‑carboxylic acid | —(a) | ≤0.3% | 0.05–0.20% |
| Unidentified oligomers | > 2200 | ≤1.0% (total) | 0.2–0.8% |
| Mesityl oxide‑derived adducts | 1420 | ≤0.1% | <0.05% |
| (a) determined by non‑aqueous titration. | |||
In comparison with furan‑2‑carbaldehyde (furfural) and thiophene‑2‑carbaldehyde, the pyrrole nitrogen imparts markedly higher electron density at the α‑position, reflected in a Hammett σm value of 0.37 versus 0.44 for furfuryl and 0.41 for 2‑thienyl. This electronic environment accelerates Schiff‑base condensation with primary amines under mild acid catalysis: with aniline at 25°C in ethanol, the pseudo‑first‑order rate constant is 3.2×10⁻³ s⁻¹, nearly 1.8‑fold that of furfural under identical conditions. Unlike furfural, which undergoes irreversible ring opening in concentrated aqueous acid, pyrrole‑2‑carbaldehyde remains chemically intact up to 2 M HCl at 50°C for 4 h, although longer exposure generates intractable oligomeric tar. The aldehyde also differs from indole‑3‑carboxaldehyde in that it does not form a stable bisulphite addition product—a consequence of the lower electrophilicity of its carbonyl carbon, estimated from 13C NMR chemical shift data to be 182.1 ppm versus 184.6 ppm for the indole analogue.
Hydrogenation of the aldehyde over Raney® nickel at 4 MPa H2 and 80°C yields 2‑hydroxymethylpyrrole, a key intermediate in several pyrrole‑based non‑steroidal anti‑inflammatory drug candidates. Exotherms exceeding 30°C·min⁻¹ have been recorded during scale‑up in a 500 L Hastelloy C‑22 autoclave, necessitating a controlled dihydrogen feed with jacket‑recirculation cooling to −5°C so that the internal temperature rise is held to <10°C above set‑point. In reductive amination protocols employing cyanoborohydride and ribose‑amine, the aldehyde competes effectively with 5‑hydroxymethylfurfural, affording 72–78% isolated yield of the pyrrolidine‑diol after silica‑gel chromatography (ethyl acetate/hexane 3:1). Spectral monitoring at λmax 287 nm (ε = 1.48×10⁴ L·mol⁻¹·cm⁻¹ in methanol) permits quantification of residual starting material down to 0.05% by HPLC‑UV calibrated against a certified reference standard.
Although pyrrole‑2‑carbaldehyde itself is not aggressively corrosive, the acidic impurities generated by autoxidation—formic acid and pyrrole‑2‑carboxylic acid—create a corrosive condensate phase when vapour contacts metal surfaces at temperatures above 60°C. Coupon testing in a 100 L glass‑lined steel reactor under 10 mbar distillation conditions showed a weight loss of 0.12 mm·year⁻¹ on Type 316L stainless steel, whereas Hastelloy C‑276 exhibited <0.01 mm·year⁻¹, in compliance with NACE MR0175/ISO 15156‑3 for sour service. Consequently, industrial vacuum‑fractionation units employ shell‑and‑tube condensers with tube‑side cladding of borosilicate glass 3.3 and tube sheets of PTFE‑lined carbon steel. Gaskets and seals must be FFKM (perfluoroelastomer) because standard EPDM swells by 12% volume after 48 h immersion at 40°C, causing leakage and contamination.
Stability trials conducted in accordance with ICH Q1A(R2) guidelines at 40°C/75% relative humidity revealed a purity decline from 99.1% to 97.8% over 6 months for an unstabilised sample stored in amber glass, driven primarily by formation of pyrrole‑2‑carboxylic acid and oligomeric species. Addition of 0.1 wt% BHT extended the shelf‑life projection based on Arrhenius modelling (activation energy 52 kJ·mol⁻¹) to 24 months at 25°C before the purity drops below the 98.0% certificate‑of‑analysis limit. Headspace oxygen in the packaging must not exceed 0.5 vol%; therefore, tote‑container filling uses nitrogen sparging through a 10 μm sintered‑metal frit for 30 min at 0.5 bar gauge pressure. Once opened, a single‑use septum‑cap system is recommended to avoid repeated exposure; repackaging into smaller aliquots under argon in a glovebox (<1 ppm O2, <1 ppm H2O) is standard laboratory practice for kilogram‑scale stocks.
Vacuum fractionation at 0.3–0.8 kPa through a Sulzer DX structured‑packing column with a packing height of 1.2 m yields a heart cut boiling at 82–84°C (pressure‑corrected to 760 mmHg) with a purity exceeding 99.5% by GC area. A reflux ratio of 4:1 is required to suppress carryover of the 2‑methylpyrrole impurity, which exhibits a relative volatility of only 1.08 to the main component. For heat‑sensitive applications, a short‑path wiped‑film evaporator operating at a jacket temperature of 100°C and a feed rate of 2 L·h⁻¹ reduces residence time to <30 s, thereby limiting dimer content to <0.05% as determined by size‑exclusion chromatography calibrated against polystyrene standards (ASTM D5296).
For use as a starting material in active pharmaceutical ingredient synthesis, the colour specification demands an absorbance of less than 0.05 AU at 430 nm in a 10 mm cell (neat liquid), aligned with the monograph of the European Pharmacopoeia. Unexpected darkening to an APHA colour of 200 on a production batch was traced to iron contamination at 12 ppm (measured by ICP‑OES per ASTM D5185), which catalysed oxidative oligomerisation. Post‑treatment with 0.3 wt% activated carbon (Norit SX Plus) under nitrogen agitation for 2 h at 40°C, followed by filtration through a 0.2 μm PTFE membrane, reduced colour to <50 APHA without affecting aldehyde titre. Build specifications now incorporate total iron expressed as Fe ≤2 ppm.
Under classical Lindsey conditions, pyrrole‑2‑carbaldehyde (2 equiv) and pyrrole (16 equiv) in dichloromethane catalysed by boron trifluoride etherate at 0.1 mol% produce meso‑pentafluorophenyl dipyrromethane after 15 min quenching with triethylamine. The product is purified by silica‑gel chromatography with dichloromethane/hexane 1:1, obtaining an isolated yield of 58% based on aldehyde. However, the hygroscopic nature of the aldehyde mandates azeotropic drying with toluene (10 mL per gram) prior to reaction, as adventitious water >100 ppm quenches the Lewis‑acid catalyst and reduces yield by approximately 25%.
Condensation with enantiomerically pure (R)‑(+)‑1‑phenylethylamine in toluene at reflux with a Dean‑Stark trap affords a chiral Schiff‑base ligand that coordinates palladium(II); the resulting complex catalyses asymmetric allylic alkylation with enantiomeric excess up to 92% ee (HPLC on Chiralpak AD‑H). The ligand is isolated in 88% yield after recrystallisation from ethanol/water 7:3. In contrast, the corresponding thiophene‑2‑carbaldimine ligand delivers only 76% ee under the same conditions, highlighting the superior stereoelectronic tuning offered by the pyrrole scaffold. Density functional theory calculations (B3LYP/6‑31G(d)) assign the difference to a more rigid chelate ring with a bite angle of 87.2° versus 89.5° for the thiophene congener.
Despite the structural analogy to furfural, which readily forms phenol‑furfural novolacs, pyrrole‑2‑carbaldehyde resists acid‑catalysed polycondensation with phenol because the protonated aldehyde requires a Hammett acidity function (H0) of approximately −2.0 for effective electrophilic attack on phenol—a condition not reached under standard novolac catalysis (oxalic acid, pH ~1). Incorporation into phenolic matrices is therefore achieved only through prior conversion to 2,5‑bis(hydroxymethyl)pyrrole via formylation, a route that adds two synthetic steps and reduces overall atom economy. Additionally, the aldehyde cannot be cured with hexamethylenetetramine in friction materials, unlike furfural, because the liberated ammonia preferentially attacks the carbonyl rather than forming methylene bridges.
