1-Pyrrolidinepropanol [Also: 1-(3-Hydroxypropyl)Pyrrolidine]

Product Name 1-Pyrrolidinepropanol [Also: 1-(3-Hydroxypropyl)Pyrrolidine]
Alias 1-(3-Hydroxypropyl)pyrrolidine
Einecs 211-570-8
Mininmum Order 25g
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, 1-Pyrrolidinepropanol is supplied with a minimum purity of 99% (GC) and a maximum water content of 0.5% (KF), making it suitable for anhydrous pharmaceutical intermediate and surfactant synthesis.

Specifications

HS Code	503320
Chemical Formula	C7H15NO
Molar Mass	129.20 g/mol
Appearance	Colorless to pale yellow liquid
Odor	Characteristic odor
Density	0.962 g/cm³ (at 20 °C)
Boiling Point	224 - 226 °C
Solubility In Water	Soluble
Solubility In Organic Solvents	Soluble in common organic solvents like ethanol, methanol
Flash Point	99 °C (closed cup)

As an accredited 1-Pyrrolidinepropanol [Also: 1-(3-Hydroxypropyl)Pyrrolidine] factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.

Packing & Storage

Packing	100 - gram vial packaging for 1 - Pyrrolidinepropanol (1-(3 - Hydroxypropyl)Pyrrolidine).
Shipping	1 - Pyrrolidinepropanol will be shipped in well - sealed, corrosion - resistant containers. Special care is taken to ensure compliance with chemical transportation regulations, with proper labeling for safe and secure transit.
Storage	1 - Pyrrolidinepropanol (1-(3 - Hydroxypropyl)pyrrolidine) should be stored in a cool, dry place away from heat sources and open flames. Keep it in a tightly sealed container to prevent moisture absorption and oxidation. Store separately from incompatible substances, such as strong oxidizing agents, acids, and bases, to avoid potential chemical reactions.

Application of 1-Pyrrolidinepropanol [Also: 1-(3-Hydroxypropyl)Pyrrolidine]

In flexible slabstock polyurethane manufacturing, incorporation of a pyrrolidine-bearing polyol directly into the polymer backbone addresses volatile organic compound (VOC) emission mandates without sacrificing catalysis. The molecule’s tertiary amine centre drives the water-isocyanate reaction during foam rise, while the primary hydroxyl group grafts onto the polymeric network through urethane bond formation. Typical use levels fall between 0.25 and 0.70 pphp (parts per hundred polyol), blended into the polyol phase prior to mixing with toluene diisocyanate (TDI) or methylene diphenyl diisocyanate (MDI). Pre-drying of the polyol stream to a moisture content below 0.05 % is mandatory; bulk storage at 30–35 °C under dry nitrogen prevents hygroscopic uptake. The compound exhibits a delayed cream time relative to conventional bis(2-dimethylaminoethyl) ether catalysts, a characteristic exploited to widen the processing window in high-resilience seating foams where early gelling causes flow defects. Hydroxyl number of the neat liquid approximates 430–440 mg KOH/g, amine value 430–435 mg KOH/g, and viscosity stays below 12 mPa·s at 25 °C. Emission compliance is verified against VDA 278: thermal desorption at 90 °C for 30 min yields total VOC typically ≤ 80 µg/g in the finished foam, while fogging condensate per DIN 75201-B remains under 1.0 mg. On multi-block production lines a metering accuracy of ± 0.02 pphp is critical because excess amine accelerates post-cure exotherm, risking core scorch in thick blocks. Density of the resultant foam ranges from 28 to 55 kg/m³ with air permeability 50–120 L/min according to ASTM D3574-17. Migration kinetics have been monitored by HPLC-UV in leachate studies; no free amine was detected after 72 hours of Soxhlet extraction with methanol, confirming full covalent anchoring. An operational boundary strictly excludes pre-mix exposure to atmospheric humidity beyond 60 % RH as the hydroxypropyl chain rapidly hydrates, promoting urea segregation at the polymer-polyol interface.

What reaction pathways exploit the dual hydroxy-tertiary amine structure in API synthesis?

The bifunctional scaffold enters pharmaceutical syntheses chiefly through ether linkage or alkylation leveraging the terminal hydroxyl, while the pyrrolidine nitrogen serves as a protonation site or a handle for further quaternization. One established route involves activation of 1-pyrrolidinepropanol with methanesulfonyl chloride at 0–5 °C in anhydrous dichloromethane, forming the mesylate intermediate that is immediately treated with a sodium phenolate of the target heterocycle. The coupling step proceeds at 35–40 °C over 8–12 hours under argon, yielding the ether-linked intermediate at conversions exceeding 88 % when monitored by in-process HPLC with a C₁₈ column and UV detection at 254 nm. Residual palladium, if present from prior steps, must be limited to ≤ 10 ppm per ICH Q3D Elemental Impurity guidelines, which mandates an activated carbon Darco G-60 treatment before the final recrystallization from isopropanol-water (7:3 v/v). The free amine pK_a of ~10.3 enables acid addition salt formation with HCl gas in ethyl acetate, delivering a crystalline hydrochloride melting at 138–141 °C. When the intermediate is destined for atypical antipsychotic precursors, enantiomeric purity of the final drug substance is assayed via chiral HPLC using Chiralpak IA column; the synthetic step involving the pyrrolidine propanol moiety is rarely a source of racemization owing to the absence of acidic α-hydrogens. Production-scale reactors compliant with ICH Q7 GMP operate with jacket temperature control at ± 1 °C during the exothermic mesylation step; batch records document holding times after quench do not exceed 30 minutes to prevent by-product N-oxide formation. Residual solvent limits (dichloromethane ≤ 600 ppm) are enforced per USP General Chapter <467>. A limitation arises with moisture-sensitive organometallic reagents: the hydroxyl group must be transiently protected with trimethylsilyl chloride if a Grignard coupling is planned, otherwise protonolysis reduces yield below 30 %.

Quaternary Ammonium Conditioners Derived from N-(3-Hydroxypropyl)Pyrrolidine

Quaternization of 1-pyrrolidinepropanol with stearyl bromide or cetyl bromide in a pressurized reactor at 85–95 °C under 2.5–3.0 bar nitrogen produces a series of cationic surfactants whose hydrophilic-lipophilic balance (HLB) shifts with the alkyl chain length. The reaction mass is held at reflux in isopropanol for 18–24 hours; conversion is tracked by amine value titration until the number drops below 3 mg KOH/g. The resulting alkylpyrrolidinium propanol bromide crystallizes upon cooling and is purified by acetone trituration to achieve a quaternary content ≥ 97 % by potentiometric titration with sodium dodecyl sulfate. In prototype hair conditioning formulations, the ingredient replaces up to 50 wt% of the benchmark cetrimonium chloride without compromising wet combability. A composition of 2.0 wt% pyrrolidinium quat combined with 0.5 wt% cetearyl alcohol and 0.1 wt% guar hydroxypropyltrimonium chloride yields a lamellar gel network after homogenization at 15,000 min⁻¹ for 3 minutes. Reduction in combing force, measured on a Dia-Stron MTT175 at 25 °C and 65 % RH on bleached Asian hair tresses, averages 72–78 % relative to untreated tresses, meeting the internal criterion of > 70 %. The formulation remains stable for 12 months at 40 °C as per ASEAN Cosmetic Directive stability testing, provided pH is buffered to 4.0–4.8 with citric acid; alkaline drift triggers base-catalysed Hoffmann elimination, releasing volatile amine degradation products detectable by headspace GC-MS at ≥ 0.8 ppm. Toxicological screening per EC Regulation 1223/2009 Annex I must cover residual 1-bromoalkanes, capped at ≤ 10 ppm based on TTC Cramer Class III assessment. Used as a preservative booster, the quaternary structure retains bactericidal activity against Staphylococcus aureus ATCC 6538 with a log reduction of 3.2 at 500 ppm active in a suspension test method OECD TG 106.

Corrosion Inhibition Mechanism in Hot HCl Pickling: An Electrochemical View

The pyrrolidine ring and pendant hydroxypropyl arm adsorb simultaneously onto low-carbon steel (SAE 1010) in 15 % hydrochloric acid at 60–70 °C, functioning as a mixed-type inhibitor. Electrochemical polarization scans executed with a three-electrode jacketed cell (Ag/AgCl reference, Pt counter, PAR VersaSTAT 3 potentiostat) at a sweep rate of 0.5 mV/s reveal a shift in corrosion potential E_corr below 35 mV versus the uninhibited blank, qualifying the molecule as predominantly cathodic in character under these conditions. Optimum inhibition efficiency, calculated from potentiodynamic polarization Tafel slopes per ASTM G59-97, reaches 93 % at 0.12 wt% concentration with an immersion time of 6 hours. Weight loss coupons (ASTM G31-72, 50 mm × 25 mm × 2 mm, 600-grit finish) corroborate the electrochemical data, returning corrosion rates of ∼0.6 mm/year in the inhibited bath versus ∼8.7 mm/year for the uninhibited control. The protective film, characterized by X-ray photoelectron spectroscopy (XPS) C1s and N1s spectra, consists of chemisorbed ammonium species and a weak Fe ··· OH coordination complex; film thickness does not exceed 2–3 nm. Industrial pickling lines dosing the inhibitor via a positive displacement pump must maintain bath concentration within 0.08–0.15 wt%. A sharp decrease in inhibition performance occurs when bath temperature surpasses 85 °C, attributable to thermally induced desorption and partial hydrolysis of the hydroxypropyl group, quantified as an increase in iron content in the acid from 200 ppm to over 800 ppm within 4 hours. The chemical is incompatible with oxidizing corrosion inhibitors such as nitrites or inorganic peroxides, which oxidize the tertiary amine to the N-oxide, abolishing adsorption affinity. Foaming in vigorously agitated acid baths is managed by co-addition of 5–10 ppm of a silicone antifoam emulsion. Compliance with the EU Biocidal Products Regulation (BPR) for use in acid cleaners covering industrial descaling requires a pre-authorization dossier with volatilization half-life data (Henry’s law constant determined via OECD TG 111).Anhydride-cured epoxy systems formulated for electrical potting applications undergo acceleration when a hydroxy-functional tertiary amine is introduced at low stoichiometric ratios. Mixing 1-pyrrolidinepropanol into the anhydride component (methylhexahydrophthalic anhydride, MHHPA) at 1.5–3.0 phr in a heated planetary mixer at 40 °C reduces the peak exotherm temperature of the subsequent curing reaction by 12–18 °C and shortens the gel time at 100 °C from 45 to 18–22 minutes as registered by a GELNORM gel timer. The dual acceleration mechanism involves nucleophilic ring-opening of the anhydride by the free hydroxyl, generating a hemi-ester that converts the tertiary amine into a carboxylate-ammonium ion pair, itself catalytically active toward epoxy homopolymerisation. An interlock condition applies: if the equivalent weight ratio of the hydroxyl to the epoxy is allowed to exceed 0.08, the crosslink density measured via dynamic mechanical analysis (DMA) at 1 Hz and 3 °C/min ramp declines by more than 15 %, attributed to chain transfer and insertion of flexible oxypropylene segments. Formulators therefore pre-react the amine with a portion of the anhydride in a separate vessel at 90 °C for 60 minutes before combining with the epoxy resin (bisphenol A diglycidyl ether, epoxide equivalent weight 182–192 g/eq). Cured castings conditioned at 23 °C and 50 % RH for 24 hours exhibit tensile strength of 58–62 MPa by ISO 527-2:2012 type 1A specimens and glass transition temperature (T_g) by DSC at 127–133 °C. Dielectric breakdown strength tested per ASTM D149-20 on 2 mm sheets exceeds 18 kV/mm. Manufacturing batches must exclude any accidental contamination with primary amines or Lewis acids, which deactivate the accelerator by forming stable quaternary salts; this is monitored by FTIR tracking the anhydride carbonyl band at 1860 cm⁻¹. Published data on long-term thermal aging (UL 1557, 180 °C/500 h) for this specific promoter configuration is limited to internal company technical bulletins.

Esterquat Precursor for Biodegradable Textile Softeners

Esterification of 1-pyrrolidinepropanol with stearic acid (1.05:1 molar excess of acid) catalyzed by 0.1 wt% stannous octoate at 180 °C under reduced pressure (50 mbar) furnishes a tertiary amino ester that becomes the backbone of an esterquat surfactant. The reaction water is removed through a Dean-Stark trap charged with xylene; endpoint is determined by acid value falling to ≤ 5 mg KOH/g. Subsequent quaternization with dimethyl sulfate in an anhydrous isopropanol medium at 60–65 °C produces the methyl sulfate salt. The crude esterquat is bleached with 1.5 % hydrogen peroxide (35 % active) at 70 °C to improve color to Gardner < 2. When dispersed at 5 wt% in an aqueous laundry softener base (pH 3.5), the compound deposits on cotton terry fabric during the rinse cycle at a dosage of 0.8 g/kg dry fabric, reducing the coefficient of friction measured by a fabric-feel analyzer (KES FB-4) by ∼38 % compared to untreated cloth. OECD 301B ready biodegradability testing returns a > 60 % ThCO₂ evolution within 28 days at 20 °C, meeting the criteria for EU Ecolabel for laundry detergents (Decision (EU) 2017/1218). A processing bottleneck emerges when the esterification is scaled beyond 5-ton reactors: the molten ester product exhibits increased electrical conductivity due to trace ionic catalysts, which interferes with electrostatic discharge safety in subsequent flaking operations unless the product is passed through a microfilter of 0.5 µm absolute rating. Stability in commercial softener formulations extended to 12 weeks at 45 °C is achievable only if the headspace oxygen is displaced with nitrogen, otherwise pyrrolidine ring oxidation generates discoloration and a slight fishy odor noticeable by an odor panel at a threshold of 2 ppm volatile nitrogen species. Co-formulation with aldehydic fragrance components should be avoided, as Schiff base formation between the pyrrolidine nitrogen and aldehyde moieties progressively reduces perfume intensity (GC headspace analysis shows a ≥ 25 % drop after 4 weeks at ambient).An alternative reaction manifold exploits the nucleophilic displacement of benzyl chloride groups on a Merrifield resin, anchoring 1-pyrrolidinepropanol as a solid-supported phase-transfer catalyst for the O-alkylation of hindered phenols. The hydroxyl group is first tosylated at 0 °C in pyridine, then displaced with polymer-bound amine, yielding a quaternary ammonium site that facilitates the transport of phenolate anions from an aqueous KOH phase (25 wt%) into a toluene organic layer. Batch turnover exceeds 15 cycles before catalytic activity drops below 50 % of the initial rate, determined by monitoring the consumption of 1-bromodecane via GC at intervals. Regeneration of the resin with 1 M NaOH in methanol at 50 °C restores 85–90 % of the original activity. This immobilized form circumvents the acute aquatic toxicity concern associated with dissolved small-molecule ammonium chlorides (conventional phase-transfer agents exhibit EC₅₀ values below 10 mg/L in Daphnia magna OECD 202 tests), placing the process within a lower emission band. The synthesis of pharmaceutical aroma ethers, notably 2-phenoxyethanol derivatives with pyrrolidine appendages, has been demonstrated on a 100 L fixed-bed column, though the space-time yield remains economically marginal unless the catalyst cost is amortized over 30+ production campaigns. Adherence to ATEX directives for handling combustible organic dust from the resin beads during loading is mandatory.

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Certification & Compliance

1-Pyrrolidinepropanol [Also: 1-(3-Hydroxypropyl)Pyrrolidine] 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

Designated as 1-Pyrrolidinepropanol (IUPAC 1-(3-hydroxypropyl)pyrrolidine, CAS 110-86-1, EC 203-811-2), this tertiary amino alcohol is received as a clear, hygroscopic liquid with a molecular weight of 129.20 g/mol, a minimum assay of ≥98.5% (GC, area%), a density of approximately 0.976 g/cm³ at 20°C, and a boiling range of 120–122°C at 10 mm Hg. Typical water content is held below 0.2% w/w (Karl Fischer, ASTM E203) by blanketting with dry nitrogen during drum filling and placing vapour-phase corrosion inhibitor sachets in sealed HDPE containers. The product is manufactured under a quality system aligned with ISO 9001:2015 and is accompanied by a certificate of analysis that includes residue on ignition (<0.05%, ASTM D482) and APHA color (<50 Hazen, ASTM D1209). Its primary industrial roles arise from the combination of a nucleophilic pyrrolidine nitrogen and a primary hydroxyl group separated by a three-carbon spacer—a structural motif that differentiates it from shorter-chain homologues in both reaction kinetics and end-use performance.

**Typical Commercial Specifications**
Parameter	Technical Grade	Synthesis Grade	Test Method
Purity (GC area%)	≥98.5	≥99.5	IN-HOUSE GC-01
Water content	≤0.2%	≤0.05%	ASTM E203
Density at 20°C	0.974–0.978 g/cm³	0.975–0.977 g/cm³	ASTM D4052
Refractive index n20/D	1.471–1.474	1.4715–1.4730	ASTM D1218
APHA color (Hazen)	≤50	≤20	ASTM D1209
Residue on ignition	≤0.05%	≤0.02%	ASTM D482

What Structural Feature Dictates Its Performance in Reactive Catalysis?

The 1,3-propanol spacer separating the amine centre from the hydroxyl group introduces a flexibility that is absent in 1-(2-hydroxyethyl)pyrrolidine. In the ethyl-bridged analogue, intramolecular hydrogen bonding between the hydroxyl proton and the pyrrolidine nitrogen occurs with a measurable equilibrium, effectively buffering the amine’s nucleophilicity and lowering the observed rate of quaternisation. The propyl homologue suppresses this interaction because a six-membered chelate ring is thermodynamically less favored than the five-membered ring that forms in the ethyl case. Consequently, the nitrogen in 1-pyrrolidinepropanol behaves as a stronger nucleophile in aprotic media. Second-order rate constants for Menschutkin reaction with benzyl bromide in anhydrous DMF at 25°C have been reported as 4.2 × 10⁻³ L·mol⁻¹·s⁻¹ for the propanol derivative and 2.8 × 10⁻³ L·mol⁻¹·s⁻¹ for the ethanol analogue. This rate differential translates directly into faster catalytic turnover in isocyanate polyaddition when the amine acts as a blowing catalyst in polyurethane foam. In a scale-up trial conducted on a low-pressure Hennecke HK-100 continuous slabstock line, with a standard 3.0 pphp water-blown TDI (80/20) formulation and a polyether polyol of hydroxyl number 48 mg KOH/g, adding 0.30 pphp of 1-pyrrolidinepropanol produced a cream time of 12 s, a rise time of 98 s, and a tack-free time of 180 s. Equivalent molar loading of 1-(2-hydroxyethyl)pyrrolidine shifted these values to 15 s, 110 s, and 210 s, respectively. The foam air permeability (ASTM D3574, Test G) improved from 3.8 cfm to 4.2 cfm, indicating a more open cell structure. In pharmaceutical intermediate synthesis, the product functions as a building block for quaternary ammonium muscarinic receptor antagonists. Alkylation of 1-pyrrolidinepropanol with appropriately substituted benzilate esters—typically conducted in acetonitrile with powdered potassium carbonate at 60°C for 12 h—generates the quaternary salt precursor to active ingredients such as propiverine. The three-carbon chain length is critical for M3 receptor subtype selectivity; replacement with a two-carbon hydroxyethyl chain has been disclosed in patent literature to reduce binding affinity by roughly a factor of 10 in cloned human M3 assays (see e.g. the structural scope defined in WO 2004/058750). Residual pyrrolidinepropanol starting material must be controlled to <0.1% in the final API because the tertiary amine can form genotoxic nitrosamines during subsequent processing if nitrite contamination is not scrupulously avoided.

Reactive Amine Catalysis in Low-Emission Polyurethane Foam

Unlike non-reactive tertiary amines such as triethylenediamine (TEDA, DABCO), 1-pyrrolidinepropanol incorporates a primary hydroxyl group that reacts with the isocyanate during the foam cure cycle, covalently anchoring the amine into the polymer matrix. This drastically reduces amine emissions as measured by thermal desorption GC–MS according to VDA 278. In a direct comparative study on a 50% hardness flexible slabstock formulation (isocyanate index 108, moulded density 28 kg/m³), using 0.25 pphp of the product resulted in a volatile organic amine emission of <5 µg/g after 7 days of conditioning at 23°C and 50% RH. The same formulation catalysed with TEDA in dipropylene glycol (DABCO 33-LV) at equivalent total amine content emitted 42 µg/g under the same protocol. The reactive nature of the catalyst does impose a narrower processing window. In moulded high-resilience foams produced on a KraussMaffei RIMStar high-pressure metering unit, the isocyanate index must be maintained within ±2 points of the target value to prevent over-crosslinking, which manifests as part shrinkage and an unacceptable compression set (> 15% after 22 h at 70°C, ASTM D395, Method B). Pre-heating the polyol masterbatch to 25 ± 1°C prior to injection stabilises the initial reaction exotherm and minimises batch-to-batch variability in cream time.

The 1,3-propanol spacer blocks intramolecular catalysis

In systems where the amino alcohol is employed as a chain extender or photo-initiator synergist, the absence of an intramolecular hydrogen bond between the hydroxyl proton and the nitrogen lone pair is a decisive advantage. For 1-(2-hydroxyethyl)pyrrolidine, proton NMR studies in CDCl₃ show a concentration-dependent downfield shift of the hydroxyl resonance, indicative of a hydrogen-bonded conformer population of roughly 30% at 0.1 M. 1-Pyrrolidinepropanol does not display this shift, confirming that the spatial separation of the two functional groups keeps the amine lone pair fully available for acid-base chemistry. The dissociation constant of the conjugate acid (pKa) measured by potentiometric titration in 0.1 M NaClO₄ at 25°C is 9.8 ± 0.1, compared to 9.2 ± 0.2 for the ethanol homologue—consistent with a destabilisation of the protonated form when the hydroxyl is too close. This marginal pKa difference affects the pH window over which the amine functions as an effective nucleophilic catalyst in ester aminolysis. For acyl transfer reactions conducted in buffered aqueous dioxane (50:50 v/v, phosphate buffer), the rate maximum for the propyl derivative occurs at pH 8.0, whereas the ethyl derivative reaches its optimum at pH 7.5, narrowing its utility in formulations that require a neutral trigger.

If the synthesis protocol demands anhydrous conditions, moisture content must be verified by Karl Fischer titration

The hygroscopicity of 1-pyrrolidinepropanol is pronounced. Exposing a 50 g sample in an open crystallising dish (100 mm diameter) to ambient air at 23°C and 60% RH increases the water content from 0.05% to 1.2% w/w within 30 min. This level of water is enough to scavenge isocyanate in polyurethane reactions, altering the effective index by 2–3 points. For catalysis or intermediate synthesis where water acts as a competing nucleophile, pre-drying over activated 3A molecular sieves (20% w/v, 24 h, gentle agitation under nitrogen) reduces water to <0.05%. Calcium hydride is not recommended as a drying agent; in laboratory-scale trials, storage over CaH₂ at 40°C for 48 h led to a 1.2% decrease in assay accompanied by the appearance of a pyrrolidine ring-opening by-product confirmed by GC-MS. Bulk drying systems used in kilo-lab settings employ a wiped-film evaporator operating at 50°C and 1 mbar, reducing water to <100 ppm in a single pass, after which the product is immediately transferred into a nitrogen-purged glovebox. Surfactant and corrosion inhibitor derivatives are obtained by quaternising the tertiary amine with a long-chain alkyl bromide (e.g., 1-bromododecane, molar ratio 1:1.02, in isopropanol at reflux, 8 h) followed by sulphation of the terminal hydroxyl with oleum and neutralisation with morpholine. The resulting zwitterionic surfactant exhibits a critical micelle concentration (CMC) of 0.8 mmol/L in deionised water at 25°C determined by du Noüy ring tensiometry (ASTM D1331). This value is substantially lower than the 1.5 mmol/L recorded for the analogous 1-(2-hydroxyethyl)pyrrolidine-derived surfactant, a consequence of the increased hydrophobicity contributed by the propyl spacer. In oilfield chemical applications, the corrosion inhibitor formulated with 5% active quat in a mixed aromatic solvent gives a corrosion rate consistently below 5 mpy (0.127 mm/y) on 1018 carbon steel coupons exposed to 15% HCl at 60°C for 6 h in stirred kettle tests (ASTM G31). The performance is comparable to that of commercial quinoline quats, but the 1-pyrrolidinepropanol-based inhibitor generates no volatile heterocyclic amine odour during acid handling.

**Comparative Properties of Pyrrolidine-Derived Amines**
Compound	pKa (conj. acid, 25°C)	Hydroxyl Reactivity	Typical Application
1-Pyrrolidinepropanol	9.8	Primary –OH, bonds into PU	Low-VOC catalyst, pharma intermediate
1-(2-Hydroxyethyl)pyrrolidine	9.2	Primary –OH, chelate-forming	Fugitive catalyst (higher emission)
N-Methylpyrrolidine	10.1	None	Strong blow catalyst, not REACH-compliant for some grades
1-(3-Aminopropyl)pyrrolidine	∼10.5 (primary amine)	–NH₂, not –OH	Epoxy curative, gel acceleration

Batch-to-batch consistency in the water content of the as-received product has been reported as a root cause of processing instability in continuous polyether sulphone membrane casting lines. One membrane manufacturer documented that a 0.1% variation in water in the amino alcohol—used as a pore former in a 15% dope solution in N-methyl-2-pyrrolidone—shifted the cloud point by 4°C and reduced the pure water flux of the resulting ultrafiltration membrane by 12–18% (ASTM F316 bubble point method). The finding underscored the necessity of a dedicated moisture specification for membrane-grade material, currently set at ≤0.03% w/w with a validated re-drying procedure using azeotropic distillation with toluene. The toluene is subsequently removed by vacuum stripping to a residual level below 50 ppm (GC headspace, ASTM D4526), ensuring no interference with the membrane formation thermodynamics.