Pyrrole, Tetrahydro-
|
HS Code |
617964 |
| Chemical Formula | C4H9N |
| Molar Mass | 71.12 g/mol |
| Appearance | Colorless liquid |
| Odor | Faintly ammoniacal |
| Density | 0.879 g/cm³ |
| Boiling Point | 88 - 92 °C |
| Melting Point | -63 °C |
| Solubility In Water | Slightly soluble |
| Vapor Pressure | 13.3 kPa (22.5 °C) |
| Flash Point | -12 °C |
As an accredited Pyrrole, Tetrahydro- factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 100 - gram bottle packaging for Tetrahydro - Pyrrole chemical. |
| Shipping | Tetrahydro - Pyrrole is shipped in tightly - sealed, corrosion - resistant containers. Adequate labeling indicates its nature. It's transported with safety measures due to its chemical properties, following regulations for hazardous chemicals. |
| Storage | Tetrahydro - pyrrole should be stored in a cool, well - ventilated area, away from heat sources and open flames. It should be stored in tightly sealed containers to prevent evaporation and contact with air. Keep it separated from oxidizing agents, acids, and bases. Due to its flammable nature, store it in a storage facility compliant with flammable liquid regulations. |
A production-scale acid copper electrolyte for high-aspect-ratio through-hole plating delivers a surface-to-hole thickness ratio below 2.0:1 when pyrrolidine is maintained at 20–30 mg/L alongside 50–70 ppm chloride ion and 2–4 mL/L of a polyalkylene glycol suppressor. The bath circulates through a horizontal conveyorised line equipped with insoluble iridium-oxide-coated titanium anodes at a cathode current density of 25–28 A/dm². Hull Cell evaluation using a 267 mL air-agitated panel at 3 A for 5 min confirms a semi-bright mid-current density zone extending from 2–7 cm from the high-current edge, reflecting the leveller adsorption on protrusions. Pyrrolidine competes with the bis-(sodium sulfopropyl)-disulfide brightener and modulates the deposition overpotential, suppressing plating at asperities while allowing sufficient throw inside 0.25–0.35 mm diameter vias. Continuous dosing is achieved via a chemical feed pump linked to real-time amp-hour metering; consumption averages 1.2–1.8 g pyrrolidine per 1,000 Ah. The accumulation of breakdown by-products above 500 ppm total organic carbon necessitates periodic activated-carbon purification with a 5-micron cartridge filter to prevent nodular burning and step-plating defects. Cross-section analysis per IPC-TM-650 method 2.2.12 must show a ductile deposit with an elongation of 8–12% and a tensile strength exceeding 250 MPa. The additive falls outside the scope of EU RoHS Directive 2011/65/EU because the plated copper itself is exempt and the pyrrolidine is not intentionally incorporated into the final solid part. However, the line operator’s exposure to airborne amine vapour requires local exhaust ventilation capable of maintaining workplace concentration below 0.5 ppm (8-h TWA), referenced against a derived no-effect level in a REACH chemical safety assessment dossier. Finished printed circuit boards produced with this chemistry are qualified for server-grade multi-layer backplanes under IEC 61249-2-21 halogen-free requirements, with ionic cleanliness verified by IPC-TM-650 2.3.25 resistivity of solvent extract. Bath ageing tests indicate that the effective pyrrolidine window narrows to 22–27 mg/L when iron contamination exceeds 100 ppm, at which point the low-current-density area loses pale brightness and a supplementary wetting agent is temporarily doped into the make-up solution.Why does zinc pyrrolidine dithiocarbamate trigger vulcanisation onset nearly half a minute faster than zinc diethyl dithiocarbamate in pre-vulcanised natural rubber latex?High-ammonia natural latex concentrate at 0.6% ammonia, preserved with tetramethylthiuram disulfide/zinc oxide dispersion, is first stabilised with 0.5–0.7 phr potassium oleate before the zinc pyrrolidine dithiocarbamate (ZPDC) pre-compounded masterbatch is metered into the jacketed tank. ZPDC itself is synthesised by dropwise addition of carbon disulfide (1.02 mol per mol pyrrolidine) into an aqueous slurry of pyrrolidine and sodium hydroxide held below 10 °C, followed by precipitation with zinc chloride solution at pH 7.0–7.5, filtration through a plate-and-frame press, and vacuum drying at 45 °C until moisture falls below 0.3 wt%. The accelerator, dispersed at 50% active content in a ball-milled water-based paste using a sodium naphthalene sulfonate-formaldehyde dispersant, is dosed into the latex at 0.8–1.2 phr on dry rubber content. Pre-vulcanisation proceeds in a closed stirred reactor at 60–68 °C until the chloroform gel test reaches a coagulum rating of 2 to 3, which typically occurs within 90–120 min. Oscillating disc rheometry per ISO 6502-1:2018 at 150 °C yields a scorch safety time ts2 as short as 0.6–0.9 min and a positive cure rate index exceeding 20 min⁻¹ , attributable to the electron-rich pyrrolidine moiety enhancing the nucleophilic cleavage of the S–S bond in the zinc-complex, outperforming ZDEC and ZDMC in activation energy terms. The table below details comparative cure kinetics measured on a formulation containing 100 phr NR latex solids, 1.0 phr sulphur, 0.5 phr zinc oxide and 1.0 phr test accelerator.
Pyrrolidine as a critical amine source in the pyrrolidinyl-ethylamine side chain of benzamide atypical antipsychoticsProcess development for the kilogram-scale synthesis of the N-(2-hydroxyethyl)pyrrolidine intermediate for sulpiride-class active pharmaceutical ingredients starts with a clean, anhydrous pyrrolidine feedstock having a purity of ≥99.5% by GC and water content below 0.2%. In a 500 L glass-lined reactor under nitrogen pad, 1.00 molar equivalent of pyrrolidine is dissolved in anhydrous methanol at 0–5 °C, and ethylene oxide (1.05 equivalents) is gradually charged via a dip tube over 4–5 h while maintaining the jacket temperature at −5 °C. After an additional 2 h of post-reaction stirring, the excess ethylene oxide is stripped by a gentle nitrogen purge, and the crude N-(2-hydroxyethyl)pyrrolidine is fractionally distilled at 85–90 °C under reduced pressure (15–20 mbar) to achieve an assay of ≥98.5% and a yield of 88–92% of theory. The intermediate is then converted to the chloroethyl analogue by treatment with thionyl chloride in toluene at 35–40 °C, quenched, and immediately dissolved in a liquid ammonia-methanol mixture within a stainless steel high-pressure autoclave rated to 40 bar for the final amination to N-(2-aminoethyl)pyrrolidine. Residual pyrrolidine in the final API side chain must be controlled to ≤720 ppm as per the Class 2 solvent limit of ICH Q3C(R8), verified by headspace gas chromatography with a flame ionisation detector. The entire synthetic pathway is executed under ICH Q7 Good Manufacturing Practice for active pharmaceutical ingredients, with critical process parameters—ethylene oxide addition rate, distillation reflux ratio, hydrogen chloride gas evolution—bindingly recorded for each batch. The resulting side chain is acyled with a methoxy-substituted benzoic acid derivative to produce racemic sulpiride or, after resolution with L-tartaric acid, levosulpiride, which must conform to the identification and assay monograph of the European Pharmacopoeia Ph. Eur. 10.5. A Certificate of Suitability to the monographs of the European Pharmacopoeia (CEP) dossier for this intermediate includes a dedicated section on the genetic stability of residual pyrrolidine, demonstrating non-mutagenic potential through an Ames test conducted per OECD 471 at concentrations up to 5000 µg/plate. Commercial-scale manufacture of the final dosage form for the Japanese and Korean markets additionally requires nitrosamine risk evaluation according to EMA/CHMP/428694/2019 and demonstration that any N-nitrosopyrrolidine formed during synthesis is purged to below the threshold of toxicological concern of 18 ng/day. The entire train of reactions is incompatible with copper or brass fittings, which catalyse pyrrolidine oxidative degradation; Hastelloy C-22 or PTFE-lined pipework is mandatory from the feed tank through the distillation column.When pyrrolidine substitutes morpholine as the co-catalyst in a pour-in-place rigid polyurethane foam for appliance insulationA polyether polyol premix based on a sucrose/glycerol-initiated oxypropylated backbone with a hydroxyl number of 380–420 mg KOH/g is doped with 0.25–0.40 pphp (parts per hundred polyol by weight) pyrrolidine and 1.2–1.8 pphp potassium octoate, while the isocyanate component is a polymeric MDI with a NCO content of 31.0–32.0%. On a Cannon A40 high-pressure continuous laminator, metered at an isocyanate index of 115–125 and a total throughput of 40–60 kg/min, the blend exhibits a cream time of 16–20 s, a string gel time of 45–52 s, and a tack-free time of 65–75 s at a pour temperature of 22 °C. Pyrrolidine drives the water-isocyanate blowing reaction preferentially, generating carbon dioxide and creating a fine, uniform cell structure with an average cell diameter of 160–190 µm as analysed by scanning electron microscopy on a sample cut with a microtome at −120 °C. The resulting free-rise core density settles at 28–32 kg/m³, and the closed-cell content measured by gas pycnometry per DIN EN ISO 4590:2016 remains above 93%. Thermal conductivity after 25 days of ageing at 23 °C/50% RH is 0.0200–0.0215 W/m·K following DIN EN 14315-1, which meets the performance brackets for refrigerated appliance panels. The strong, characteristic amine smell of pyrrolidine, however, necessitates a post-foam curing zone swept with a 3,000 m³/h exhaust air system; residual amine emissions from the cut panels must remain below the AgBB scheme threshold of 1.0 µg/m³ TVOC after 28 days in a test chamber according to ISO 16000-6. The catalyst is not transferred directly into food contact; thus no specific food-contact plastics regulation applies, but the whole foam formulation must be registered under EU REACH Regulation (EC) 1907/2006 with a dermal DNEL for pyrrolidine set at 2.5 mg/kg bw/day in the safety data sheet. In freezer cabinets manufactured by sequential foaming between pre-positioned steel shells and ABS inner liners, the flowability window is 12–15 seconds shorter than with dimethylcyclohexylamine, so the line speed must be reduced by approximately 5% to prevent underfill at the unit’s extremities; in compensation, the slightly lower reactivity allows a 1.5–2.0% reduction in MDI overspray lost to the paper leader.Coupling-component selectivity of tetrahydropyrrole in modified basic red azo chromophores for polyacrylonitrile stapleDiazotised 4-nitroaniline, prepared from 138 g (1.0 mol) amine in 250 mL 30 wt% hydrochloric acid with 0.98 mol sodium nitrite at 0–2 °C, is clarified and slowly intermixed with an ice-slurry containing 1.02 mol tetrahydropyrrole and 2.8 mol sodium acetate buffer to hold the coupling pH at 4.2–4.4. The electrophilic substitution occurs exclusively at the nitrogen-bearing carbon, the strong electron-donating character of the pyrrolidine ring directing the coupling para to the incoming diazonium entity. After stirring for 6 h at 0–5 °C, the precipitated azo chromophore is filtered, washed to a conductivity ≤150 µS/cm, and vacuum dried at 50 °C to obtain a dark red powder with a melting point of 178–182 °C (decomposition). A tinctorial strength assay against a certified reference standard run on a spectrophotometer under AATCC TM 150-2015 yields a relative colour strength of 395–410%. The pure dye is milled with sodium sulphate or dextrin to standardise to 200% commercial formulation and then applied on polyacrylonitrile yarn in a package-dyeing machine at a goods-to-liquor ratio of 1:12, raising the dyebath from 70 °C to 100 °C over 45 min while maintaining the pH at 4.0–4.5 with sodium acetate/acetic acid. Light fastness tested in a Q-SUN Xenon arc apparatus per ISO 105-B02:2014 reaches 6 (blue wool scale) at full depth, and wet rubbing fastness measured with a Crockmeter under ISO 105-X12:2016 is graded at 4–5. The azo coupling process generates an effluent stream loaded with zinc chloride if metallic salts are used for dye isolation; such effluent must be treated with sodium hydroxide precipitation to reduce zinc to <2 mg/L before municipal discharge, referenced to EU Industrial Emissions Directive 2010/75/EU. Since the tetrahydropyrrole moiety is not a listed aromatic amine susceptible to reductive cleavage under the EU REACH Annex XVII entry 43, the final dyed acrylic product normally meets the OEKO-TEX Standard 100 appendix 4 limits for banned azo colourants without additional analytics. Fibre manufacturers incorporating this chromophore in blended carpets destined for the EU market must additionally certify the absence of residual monomer below the 0.1 wt% reporting threshold under the harmonised hazard classification CLP (EC) No 1272/2008 for pyrrolidine, which is classified as a flammable liquid and an acute dermal toxicant Category 4 by the notifier. The reactor level control for the dimeric azo condensation step involves an anti-fouling PTFE-coated probe, as the pigmentary character of the crude product forms hard deposits on 316L stainless steel surface roughness exceeding Ra 0.8 µm. |
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The five-membered ring of tetrahydropyrrole populates an envelope conformation with a pseudo-rotational barrier near 0.5 kcal/mol, presenting the nitrogen lone pair with less steric obstruction than the chair conformer of piperidine. In acetonitrile at 25 °C, stopped-flow UV kinetics at 400 nm gave a rate ratio kpyrrolidine/kpiperidine of 1.8–2.3 for aminolysis of p-nitrophenyl acetate under pseudo-first-order amine excess. The conjugate-acid pKa values (11.27 vs. 11.22, aqueous, 25 °C) differ by only 0.05 log units, so the kinetic advantage stems from reduced steric demand rather than a meaningful basicity shift. Morpholine (pKa 8.33) is over two orders of magnitude slower in the identical system, while pyrrole is inert. In synthesis, this translates to pyrrolidine acting as a superior leaving-group nucleofuge in active-ester coupling; its hydrochloride salt precipitates cleanly from ethyl acetate, simplifying work-up compared to the more soluble piperidinium salt.
| Property | Pyrrolidine | Piperidine | Morpholine | Pyrrole |
|---|---|---|---|---|
| CAS number | 123-75-1 | 110-89-4 | 110-91-8 | 109-97-7 |
| Molar mass (g mol⁻¹) | 71.12 | 85.15 | 87.12 | 67.09 |
| Boiling point (°C at 101.3 kPa) | 87–88 | 105–107 | 128–130 | 129–131 |
| Density (g mL⁻¹, 20 °C) | 0.852 | 0.862 | 1.000 | 0.970 |
| pKa (conjugate acid, H₂O) | 11.27 | 11.22 | 8.33 | ~0.4 (protonation) |
| Dipole moment (D) | 1.57 | 1.19 | 1.53 | 1.77 |
| Ring member | 5 | 6 | 6 (O at 4) | 5 (aromatic) |
| Typical reaction function | Fast nucleophile | General base | Low-basicity scavenger | Resonance-stabilised, non-nucleophilic |
Commercial tetrahydropyrrole is rectified through a continuous column system of 20 theoretical plates to a heart cut distilling at 87–88 °C (101.3 kPa). Three principal product codes are available: PYR-TECH (≥98.5%), PYR-SYNTH (≥99.0%), and PYR-ANH (≥99.5%, water ≤50 ppm). Secondary amine head-space oxygen rapidly generates amine oxides and peroxides; the anhydrous grade requires stabilisation with 100–250 ppm of butylated hydroxytoluene to maintain peroxide (as H₂O₂) below 10 ppm over a 12‑month shelf life when stored under 99.99% nitrogen. Distillate density at 20 °C, measured by oscillating U-tube (ASTM D4052-22), serves as a rapid in-plant purity check; a deviation greater than 0.0005 g mL⁻¹ from the reference 0.8520 g mL⁻¹ triggers a full assay.
| Parameter | PYR-TECH | PYR-SYNTH | PYR-ANH | Test method |
|---|---|---|---|---|
| Assay (GC, area%) | ≥98.5 | ≥99.0 | ≥99.5 | ASTM D34 (FID, wax column) |
| Water (wt%) | ≤0.10 | ≤0.05 | ≤0.005 | ASTM E203-16 (coulometric KF) |
| Colour (APHA) | ≤30 | ≤20 | ≤10 | ASTM D1209-05 |
| Peroxide (as H₂O₂, ppm) | ≤50 | ≤20 | ≤10 | In-house iodometric titration |
| Non-volatile residue (mg L⁻¹) | ≤10 | ≤5 | ≤2 | ASTM D1353-13 |
| Boiling range (°C, 101.3 kPa) | 87–88 | 87–88 | 87–88 | ASTM D1078-21 |
The ammonium salt of pyrrolidine dithiocarbamate (APDC) functions as a water-borne ultra-accelerator in polychloroprene latex dipping. In a standard compound containing 2 phr zinc oxide, 0.5 phr sulfur, and a rosin acid emulsifier, an addition of 0.5 phr APDC produces a scorch time (ts2) of 1.3 min and a t90 of 4.1 min at 140 °C on a moving-die rheometer set to 0.5° arc (ASTM D5289-19a). Replacing APDC with the equimolar piperidine pentamethylene dithiocarbamate (PPDC) lengthens ts2 to 2.0 min and t90 to 5.8 min, a delay attributed to steric hindrance around the zinc-dithiocarbamate intermediate that governs sulphur cross-link insertion. The derived vulcanisate tensile strength (ASTM D412-16, Die C) is 22.7 MPa for the pyrrolidine-based cure versus 21.2 MPa for the piperidine-based cure, with elongation at break unchanged at 650%. The sharper scorch response demands that the latex bath be jacketed to ±1.5 °C to prevent premature gelation; plants without programmable logic-controlled glycol recirculation have experienced product reject rates rising above 8% when ambient-temperature swings exceed 5 °C during a shift.
Anhydrous pyrrolidine, dried over 3Å molecular sieves to water ≤30 ppm, functions as a weakly coordinating, basic medium for the preparation of lithium diisopropylamide at −78 °C, suppressing enolate formation pathways common in ethereal solvents. In palladium-catalysed Suzuki–Miyaura coupling of deactivated aryl chlorides, a pyrrolidine-ligated Pd(0) species yields turn-over frequencies above 500 h⁻¹ in anhydrous dioxane at 90 °C, outperforming triethylamine by a factor of 3. Shipping classification is UN 1922 (Pyrrolidine), Class 3 flammable liquid, Packing Group II; closed-cup flash point is −3 °C (ASTM D93-20). Long-term storage under inert gas requires a head-space oxygen level below 0.5 vol% and the addition of 100–250 ppm BHT to keep active peroxide below 5 ppm over the 12‑month re-test period. The substance is registered under REACH (EC No. 203-825-3) and appears on the TSCA inventory.
