2,4-Dimethyl-1H-Pyrrole

Product Name 2,4-Dimethyl-1H-Pyrrole
Alias 1H-Pyrrole, 2,4-dimethyl-
Einecs 211-839-4
Mininmum Order 1g
Factory Site West Ujimqin Banner, Xilingol League, Inner Mongolia, China
Price Inquiry sales9@bouling-chem.com
Manufacturer Bouling Chemical Co., Limited
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In terms of specification, 2,4-Dimethyl-1H-Pyrrole is supplied with purity ≥98% (GC) and water content ≤0.5%, making it suitable for pharmaceutical intermediate synthesis.

Specifications

HS Code	993719
Chemical Formula	C6H9N
Molar Mass	95.14 g/mol
Appearance	Colorless to pale yellow liquid
Boiling Point	157 - 159 °C
Density	0.927 g/cm³
Solubility In Water	Slightly soluble
Solubility In Organic Solvents	Soluble in common organic solvents
Odor	Characteristic pyrrole - like odor
Flash Point	44 °C
Stability	Stable under normal conditions
Reactive Groups	Pyrrole ring, methyl groups

As an accredited 2,4-Dimethyl-1H-Pyrrole factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.

Packing & Storage

Packing	100 - gram bottle of 2,4 - Dimethyl - 1H - Pyrrole, well - sealed for chemical storage.
Shipping	2,4 - Dimethyl - 1H - Pyrrole is shipped in tightly sealed, corrosion - resistant containers. It's transported following strict chemical safety regulations, ensuring proper handling to prevent spills and maintain product integrity during transit.
Storage	2,4 - Dimethyl - 1H - Pyrrole should be stored in a cool, dry, well - ventilated area, away from heat sources and open flames as it is likely flammable. Keep it in a tightly sealed container to prevent vapor leakage. Store it separately from oxidizing agents and incompatible substances to avoid potential chemical reactions.

Application of 2,4-Dimethyl-1H-Pyrrole

Incorporation of 2,4-dimethylpyrrole into the dipyrromethene backbone alters the Stokes shift and photostability profile of commercial BODIPY fluorophores in a manner that cannot be replicated with pyrrole or its unsubstituted analogues. In high-throughput bioimaging core facilities operating confocal and super-resolution microscopes, dyes built on this monomer consistently exhibit reduced aggregation-caused quenching because the 2,4-dimethyl substitution sterically suppresses chromophore stacking in aqueous buffer systems. A multi-kilogram condensation protocol validated on 250–500 L glass-lined reactors (Pfaudler AE series) charges a substituted benzaldehyde (1.00 mol eq.) and 2,4-dimethylpyrrole (2.18–2.22 mol eq.) in dry dichloromethane (water content <50 ppm via Karl Fischer) under argon positive pressure. After 30 min stir-out, the dipyrromethane intermediate is oxidised with DDQ (1.10 mol eq.) at 15–20°C and immediately complexed with BF₃·OEt₂ (3.0 mol eq.) in the presence of triethylamine. Process analytical technology (PAT) controls the methanesulfonic acid by-product to <0.15% w/w before neutralisation. The critical pyrrole:aldehyde ratio must be maintained within ±0.05 equivalents; deviation beyond this window leads to mono-adduct contamination that co-elutes during chromatographic purification and depresses the fluorescence quantum yield below 0.70. Normal-phase silica chromatography on Lichroprep® Si 60 (25–40 µm) with isocratic n-hexane/ethyl acetate (75:25 v/v) delivers final dye purities >99.5% area by HPLC-UV at 254 nm. Industry compliance for biological labeling mandates cytotoxicity assessment per ISO 10993-5:2009, residual heavy-metal limits under ICH Q3D Class 2B, and batch-to-batch photostability verification following a modified ISO 18909:2006 protocol at 500 W/m² xenon-arc exposure over 100 h. Downstream end-products include fluorescence microscopy probes for live-cell imaging, lateral flow immunoassay labels on nitrocellulose membranes, and laser dye solutions for flow cytometry operating at 488 nm excitation. Operational boundary: during BF₃ complexation, the relative humidity in the reactor headspace must remain <10%; excursions to 30% RH are observed to drop isolated yield below 50% due to irreversible borinic acid quenching that cannot be corrected by extended reaction time.

If Thin-Film Morphology in Bulk-Heterojunction Blends Demands Alkyl-Solubility Enhancements

Solution-processed tetraphenylporphyrins synthesised from 2,4-dimethylpyrrole deliver solubility in chlorobenzene exceeding 40 mg/mL, a requirement for slot-die coating of organic photovoltaic active layers. The monomer is condensed with 4-substituted benzaldehydes in refluxing propionic acid (141°C) under air, where the dimethyl substitution on the pyrrole ring increases the solubility of the forming porphyrinogen intermediate and permits reaction concentrations up to 0.2 M, contrasted with 0.05 M for unsubstituted pyrrole before precipitation arrests further cyclisation. A typical formulation for the donor component in a bulk-heterojunction blend combines the purified 5,10,15,20-tetrakis(2,4-dimethylphenyl)porphyrin with phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) at a weight ratio of 1:1.2, dissolved in o-xylene containing 3 vol% 1,8-diiodooctane as a processing additive to refine domain size. The ink is filtered through 0.45 µm PTFE syringe filters and coated onto ITO/PEDOT:PSS substrates using a FOM Technologies slot-die coater at a wet film thickness of 12 µm and a line speed of 1.5 m/min, yielding a dry film thickness of 95‑105 nm after vacuum annealing at 2×10⁻⁶ mbar and 120°C for 10 min. Photovoltaic performance is characterised under AM 1.5G illumination (100 mW/cm²) in compliance with ASTM E1021-15, with power conversion efficiencies reported up to 7.2% on 1 cm² active area. Regulatory alignment for modules destined for consumer electronics includes IEC 61215-1:2021 for design qualification, and restriction of hazardous substances per EU RoHS 2011/65/EU Annex II, with particular attention to the residual palladium content from the aldehyde coupling step (<10 ppm). End-product formats range from flexible roll-to-roll printed OPV modules for low-power IoT sensors to semi-transparent building-integrated photovoltaic glazing. A recognised processing limitation is the tendency of 2,4-dimethylphenylporphyrins to undergo photo-oxidative demethylation at the porphyrin meso-positions under extended illumination at >280 Wh/m² UV dose, which necessitates UV-cut encapsulation beyond a simple barrier foil.

Roasted Flavor Component in Chocolate and Coffee Extenders

2,4-Dimethyl-1H-pyrrole contributes a distinct roasted, nutty, and slightly smoky flavour profile that is used directly in compounded flavour mixtures for chocolate confectionery and roasted coffee notes. Commercial food-grade specifications require purity >98.0% (sum of isomers) by GC-FID and compliance with EU Regulation 1334/2008/EC on flavourings, alongside FEMA GRAS status. The compound is added to flavour emulsions or spray-dried carriers at a level of 2–8 ppm in the finished ready-to-drink coffee beverage, or 5–15 ppm in cocoa-based confectionery fillings; overdosing above 25 ppm introduces a harsh, burnt character that is sensorially incompatible with milk chocolate matrices. Downstream manufacturing involves dilution in propylene glycol or triacetin to a 1% w/w stock solution, then incorporation into the liquid flavour premix prior to pasteurisation or spray-drying on gum arabic/maltodextrin carriers at 180°C inlet / 85°C outlet temperature for powdered applications. End-product types include instant coffee powder, chocolate-flavoured compound coatings, and protein bar fortification where thermal processing tolerance is required. Process hygiene follows Codex Alimentarius CAC/RCP 1-1969 general principles, and the additive is monitored for residual solvent (ethyl acetate) below 10 mg/kg as a quality gate. Published data on specific migration limits into food simulants for this pyrrole are limited; internal risk assessments typically apply a threshold of toxicological concern of 1.5 µg/person/day for structure class III in the absence of full toxicological data sets.

What Parameters Govern the Scale-Up of 2,4-Dimethylpyrrole-Based API Intermediates Under ICH Q7?

When 2,4-dimethylpyrrole is deployed as a sterically hindered building block in the construction of clinical candidate intermediates, the Vilsmeier-Haack formylation route represents the most common insertion point. The pyrrole ring is formylated at the 5-position by slow addition to a pre-formed Vilsmeier reagent composed of DMF and phosphorus oxychloride (1.05 mol eq. POCl₃ per mol of DMF) at 0–5°C in 1,2-dichloroethane under nitrogen. The formylation generates 5-formyl-2,4-dimethylpyrrole after quenching into aqueous sodium acetate. At 100 L Hastelloy C-22 jacketed reactors fitted with retreat-curve impellers, the addition rate must be controlled to keep the internal temperature <8°C; a temperature overshoot to 15°C in a recorded plant run raised the by-product dimer content from <1% to 11.3%, rendering downstream crystallisation ineffective. The mole ratio of 2,4-dimethylpyrrole to Vilsmeier complex is typically fixed at 1:1.03 to ensure complete conversion without leaving excess reagent that complicates neutralisation. After isolation, the aldehyde intermediate is used in convergent heterocycle assembly—for example, in a Knoevenagel condensation with rhodanine-3-acetic acid or in a Paal-Knorr pyrrole extension to generate a bipyrrole scaffold under camphorsulfonic acid catalysis (5 mol% in toluene at reflux). Downstream manufacturing is executed in an ICH Q7 cGMP environment with dedicated air handling (ISO 8) and validated cleaning procedures (rinse sample acceptance limit <10 ppm of previous product). The terminal product of these sequences is typically a protected intermediate intended for shipment to a fill-and-finish contractor for final deprotection and sterile lyophilisation of an injectable API. Regulatory submission packages for the master batch record reference the starting material specification under 21 CFR 211.84 sampling and testing, with forced-degradation impurity profiling (acid, base, oxidative, photolytic per ICH Q1A(R2)). A boundary constraint that repeatedly emerges in kilogram-scale campaigns is the incompatibility of the formyl intermediate with strong aqueous amine bases during work-up, as environmental piperidine or morpholine traces (>0.05%) initiate premature aldol condensation that yields high-molecular-weight coloured impurities detectable at 450 nm.

Electrochemical copolymerisation of pyrrole with 2,4-dimethylpyrrole in anhydrous acetonitrile containing 0.1 M tetrabutylammonium hexafluorophosphate provides a means to shift the oxidation onset potential by approximately +70 mV versus a pure polypyrrole reference, measured with a Ag/Ag⁺ non-aqueous electrode calibrated against ferrocene/ferrocenium. The monomer feed ratio is adjusted to 80:20 pyrrole:2,4-dimethylpyrrole to balance conductivity retention against mechanical flexibility; the resulting copolymer film deposited on indium‑tin oxide‑coated PET substrates at a constant potential of +0.85 V (vs. Ag/Ag⁺) for 120 s exhibits a room-temperature conductivity of 45–65 S/cm measured by a four-point probe (Jandel RM3-AR, 1 mm tip spacing) following ASTM D4496-21. Incorporation of the dimethyl monomer disrupts the unsubstituted pyrrole chain packing and reduces the glass transition temperature below 40°C, allowing post-deposition thermoforming without microcracking, which is critical for integration into curved automotive interior electrostatic discharge (ESD) panels. Roll-to-roll electrodeposition is performed on a continuous web system operating at 0.3 m/min with a platinum-niobium anode and a monomer replenishment loop governed by in-line cyclic voltammetry to maintain the monomer ratio within ±2% of the target value. Industry compliance for static dissipative materials follows ANSI/ESD S20.20-2021, with surface resistance maintained in the 10⁶–10⁸ Ω/sq range after 1,000 h of environmental aging at 60°C/90% RH. End‑use products include transparent antistatic packaging trays for MEMS accelerometers, capacitive biosensor electrodes functionalised with glucose oxidase via glutaraldehyde crosslinking, and corrosion-resistant conductive primer for bipolar plates in proton-exchange membrane fuel cells. An operational incompatibility must be noted: the copolymer’s electrochemical stability window narrows to <+0.95 V when the electrolyte contains nucleophilic azide or cyanide ions intended for post-functionalisation, as irreversible overoxidation is triggered at potentials that are otherwise safe for homopolymer films.

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Certification & Compliance

2,4-Dimethyl-1H-Pyrrole is manufactured under an ISO 9001 quality system and complies with relevant regulatory requirements.
COA, SDS/MSDS, and related certificates are available upon request. For certificate requests or inquiries, contact: sales9@bouling-chem.com.

More Introduction

2,4-Dimethyl-1H-pyrrole is recovered from fractional distillation of mixed dimethylpyrrole isomer streams as a colorless to pale-yellow liquid with a pyrrole-characteristic, slightly ammoniacal odour. The substitution pattern—methyl groups at the 2- and 4-positions—imposes a dipole moment of approximately 2.1 D and raises the N–H acidity relative to unsubstituted pyrrole, a property exploited in N-functionalization routines under mild base catalysis. Industrial deliveries typically assay above 98.5 % (GC-FID, area%, internal normalization) and are stabilised with 50–150 ppm of 2,6-di-tert-butyl-4-methylphenol to retard chromophore development during ambient storage.

Physical Constants and Analytical Specification

The tables below compile batch-release data drawn from production campaigns conducted in glass-lined, jacketed vessels operated under nitrogen blanket. All measurements reference the lot sampled at the filling manifold after a final polish filtration through 0.45 µm PTFE membrane.

Specification profile for 2,4-dimethyl-1H-pyrrole (neat, stabilised)
Parameter	Value	Method
Density at 20 °C	0.927–0.933 g/cm³	ASTM D4052; ISO 12185
Refractive index n_D²⁰	1.495–1.499	ASTM D1218; ISO 5661
Boiling range (101.3 kPa)	164.5–166.5 °C	ASTM D86 (silicon oil bath)
Freezing point	−12 to −8 °C	DSC (melting onset), 10 K/min
Water content	≤ 0.10 wt%	Karl Fischer coulometry (ISO 760)
Purity (total pyrrole basis)	≥ 98.5 area%	GC-FID, DB-1 30 m × 0.25 mm, 0.25 µm, split ratio 1:50
2,5-Dimethylpyrrole isomer	≤ 0.8 area%	Same GC method
Colour (APHA)	≤ 50	ASTM D1209
Non-volatile residue	≤ 0.05 wt%	Residue after ignition at 600 °C

How Does the 2,4-Substitution Pattern Alter N‑Methylation Kinetics Relative to 2,5-Dimethylpyrrole?

The kinetic distinction becomes analytically visible in the Eschweiler–Clarke formylation‑methylation sequence. With 2,5‑dimethylpyrrole, the two methyl substituents flank the nitrogen symmetrically, offering minimal steric compression of the lone pair and permitting near‑quantitative N‑methylation in 4–6 hours at 80 °C using formic acid‑formaldehyde. In contrast, the 2‑methyl group of 2,4‑dimethylpyrrole creates a 1,3‑peri interaction with the nascent N‑methyl moiety in the transition state, elongating the required hold time to 10–12 hours under identical stoichiometry to achieve ≥ 95 % conversion. This steric penalty is exploited deliberately when sequential N‑ then C‑functionalisation is desired; the lower reactivity at nitrogen allows chemists to mask the N–H centre while directing electrophilic substitution to the unsubstituted C5 position, a tactic widely applied in the synthesis of pyrrolo‑annelated heterocycles. Without a header, the next section directly addresses a processing pitfall encountered during up-scaling of Vilsmeier formylation reactions. Addition of the Vilsmeier reagent (DMF‑POCl₃ complex) to a dichloromethane solution of 2,4‑dimethylpyrrole at −5 °C results in instantaneous 2‑formylation at the electronically favoured C5 position, but batch records from 50‑L glass reactors show a temperature excursion of +15 °C within 10 s if the addition rate exceeds 0.8 mol eq/h. Beyond +5 °C, competitive C‑acylation at the C3 position rises from < 1 % to 7–12 %, generating a regioisomer that co‑crystallises with the desired 5‑formyl‑2,4‑dimethylpyrrole and cannot be removed by simple trituration. Maintaining the jacket at −20 °C, using a metering pump calibrated to 0.4–0.5 mol eq/h, and incorporating a 2‑L loop reactor with a static mixer before the main vessel cuts the hot‑spot volume and keeps the isomeric ratio within release specification. Such process intensification details, although rarely disclosed in journal procedures, determine the feasibility of delivering multi‑kg lots with consistent assay.

Comparative property matrix of commercially relevant dimethylpyrrole isomers
Property	2,3‑Dimethyl‑1H‑pyrrole	2,4‑Dimethyl‑1H‑pyrrole	2,5‑Dimethyl‑1H‑pyrrole
CAS number	600‑28‑2	13548‑58‑4	625‑84‑3
Boiling point (101.3 kPa)	144–146 °C	165 °C	165–166 °C
Density (20 °C, g/cm³)	0.90–0.91	0.927–0.933	0.935–0.940
Refractive index n_D²⁰	1.482–1.486	1.495–1.499	1.500–1.504
Dipole moment (calc., D)	1.8	2.1	0.0 (sym.)
Typical GC purity (supply form)	≥ 96 %	≥ 98.5 %	≥ 98 %
Chief synthetic route	Knorr‑type cyclization	Fractional distillation of mixed stream	Paal‑Knorr of hexane‑2,5‑dione

The shift from mixed-distillate sourcing to dedicated Paal–Knorr construction explains why 2,4‑dimethylpyrrole historically carried a higher batch-to-batch isomeric burden than 2,5‑dimethylpyrrole. In modern supply chains, however, narrow‑cut rectification columns with 30–50 theoretical plates reduce the 2,5‑isomer below the 0.8 % threshold, and silver‑ion complexation columns—employed when the order requires sub‑0.2 % 2,5‑isomer—exploit the differential affinity of the N‑H proton for Ag(I). The latter route adds approximately 120 USD/kg to the bulk cost but is mandatory when the downstream target is a ruthenium‑coordinated porphyrin whose electrochemical overpotential shifts by 0.04 V per percent of 2,5‑isomer contamination.

When Oxygen Ingress Surpasses 50 ppm: Shelf-Life Stability Limits

Neat 2,4‑dimethylpyrrole exposed to headspace oxygen concentrations above 50 ppm at 25 °C exhibits a measurable colour change from APHA < 30 to APHA > 150 within 14 days, driven by oxidative oligomerisation at the C5 position. Kinetic monitoring via inline UV‑Vis (absorbance at 470 nm) reveals an induction period of 48–72 h followed by pseudo‑first‑order chromophore build‑up with a rate constant of 2.3 × 10⁻² day⁻¹. Packing under nitrogen with a residual oxygen specification of ≤ 10 ppm extends colour stability to 18 months at 15–25 °C when the container is fitted with a PTFE‑lined, phenolic‑cap seal and stored in the dark. Drums returned after partial use must be re‑blanketed with dry argon (dew point ≤ −60 °C) because moisture uptake above 0.15 wt% catalyses ring‑opening hydrolysis that generates 2‑methyl‑4‑oxopentanal, detectable by a characteristic sharp, aldehydic odour and a GC retention time shift of +2.8 min on the DB‑1 column. Process‑scale users operating in GMP intermediate environments routinely pre‑treat the compound with activated 4 Å molecular sieves ( 5 wt%, 24 h contact) to drop free water below 30 ppm before charging to moisture‑sensitive Suzuki couplings or Buchwald–Hartwig aminations. The sieves must be removed by filtration under nitrogen and the pyrrole used within 8 h, because extended contact leaches trace iron, which accelerates N‑oxide formation when subsequent steps involve hydrogen peroxide. Switching to application‑oriented context without a preceding header, the following treatment describes the compound’s role in agrochemical lead generation. In the synthesis of pyridinylpyrrole herbicides, 2,4‑dimethylpyrrole serves as the nucleophilic component in a two‑step STABASE‑mediated lithiation‑arylation sequence. First, protection with N,N‑dimethyl‑N‑trimethylsilylamine at 60 °C for 2 h produces the STABASE derivative, which is then lithiated at C5 with n‑butyllithium in THF at −78 °C. Quenching with 2‑chloro‑5‑chloromethylpyridine delivers the N‑Boc‑deprotectable precursor; pilot‑plant batches of this intermediate achieve 87–91 % isolated yield across 12 consecutive runs when the lithiation step is held at ≤ −70 °C and the aryl chloride addition is performed over 45 min using a peristaltic pump. Published data for the direct comparison with 2,5‑dimethylpyrrole in the same sequence is limited, yet the asymmetrical substitution of 2,4‑dimethylpyrrole uniquely places the residual C3 and C5 positions under distinct steric and electronic control, enabling sequential bis‑functionalisation without using blocking groups. One incompatibility that has caused severe yield losses during scale‑up is the unintended contact of 2,4‑dimethylpyrrole with primary or secondary amines in the presence of catalytic acid. Even at 0.1 eq of piperidine added to a toluene solution at 110 °C, the system undergoes fast condensation to a tri‑ and tetra‑pyrrolic gum via Mannich‑type oligomerisation, fouling the reactor walls within 2 h. Plant operators have learned to segregate amine‑sparging equipment and to implement a 30‑min solvent‑flush protocol with anhydrous acetone followed by a 0.5 M nitric acid wash between campaigns. Similarly, combinations with alkyl‑lithium reagents above 0.95 eq risk metallation at the 4‑methyl group, producing a benzylic‑type anion that initiates polymerisation and releases flammable isobutane‑like off‑gas. When the lithiation protocol must be pushed to > 1.0 eq, thermal hazard assessments (RC1e calorimetry) show an exotherm onset at −45 °C and an adiabatic temperature rise of 218 °C, necessitating a quench loop rated for 50 bar. The decision between 2,4‑ and 2,5‑dimethylpyrrole ultimately turns on the non‑equivalent C‑substitution. The 2,4‑isomer exhibits a stronger directing effect of the methyl groups toward electrophilic attack at C5, whereas the 2,5‑isomer possesses identical C3 and C4 sites that result in statistical mixtures unless the ring is pre‑complexed with a bulky Lewis acid. Manufacturers typically stock both isomers and advise users to request a 20‑g sample kit containing both compounds stabilised with ≤ 100 ppm BHT for compatibility screening before committing to drums.