| HS Code | 511787 |
| Productname | Diethyl Malonate |
| Iupacname | Diethyl propanedioate |
| Casnumber | 105-53-3 |
| Ecnumber | 203-305-9 |
| Molecularformula | C7H12O4 |
| Molecularweight | 160.17 g/mol |
| Appearance | Colorless liquid |
| Odor | Fruity, ester-like |
| Density | 1.055 g/cm3 at 20 °C |
| Meltingpoint | -50 °C |
| Boilingpoint | 199 °C |
| Refractiveindex | 1.414 at 20 °C |
| Flashpoint | 100 °C closed cup |
| Solubility | Slightly soluble in water; miscible with ethanol and ether |
| Purity | ≥99% |
As an accredited Diethyl Malonate factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Diethyl malonate is supplied in 1 L amber glass bottles with PTFE-lined caps, cushioned, and labeled for safe chemical storage. |
| Container Loading (20′ FCL) | Container loading (20′ FCL) for Diethyl Malonate: sealed steel drums or IBC totes, palletized, secured, and braced for ocean transport. |
| Shipping | Diethyl malonate (CAS 105-53-3) is generally shipped as a non-regulated, combustible liquid with a high flash point (~100 °C). Use appropriate, tightly closed containers. Avoid heat, sparks, oxidizers, and moisture. Label with chemical name and CAS number. Follow applicable DOT, IMDG, IATA, and local transport regulations. |
| Storage | Store diethyl malonate in a cool, dry, well-ventilated area away from heat, sparks, and open flames. Keep containers tightly closed in a flammable-liquid storage cabinet. Protect from moisture, acids, bases, and oxidizing agents. Use grounded equipment and avoid inhalation or skin contact. Maintain ventilation and keep away from incompatible materials, ignition sources, and direct sunlight. |
| Shelf Life | Diethyl malonate: typically stable two years when stored sealed in a cool, dry place, away from moisture, acids, bases, and oxidizers. |
A sealed glass-lined reactor equipped with an anchor agitator is charged with 21 wt% sodium ethoxide in anhydrous ethanol under nitrogen. Diethyl malonate (CAS 105-53-3, 160.17 g/mol, 1.055 g/mL at 20 °C) is metered below the liquid surface while the reaction mass is maintained below 15 °C. Karl Fischer titration per ASTM E203 is run before charging; the water content is maintained below 0.10 wt%. Residual moisture converts sodium ethoxide to sodium hydroxide, and the resulting hydroxide saponifies the ester groups, which depresses the yield of diethyl ethylmalonate and raises the sodium bromide extractable impurity load. The reactor is inerted because sodium ethoxide in ethanol forms a flammable headspace; the agitator seal is flushed with nitrogen at 20–30 L/min. Ethyl bromide is added at a molar ratio of 1.02–1.10 relative to diethyl malonate using a diaphragm metering pump. The first alkylation produces diethyl ethylmalonate; that product retains one acidic α-proton, so a competing second alkylation produces diethyl diethylmalonate. In-process gas chromatography on a 30 m × 0.25 mm 5 % phenyl methyl siloxane column is used to stop the ethyl bromide feed when diethyl diethylmalonate reaches 0.5 area%. The batch is quenched with acetic acid and ethanol is recovered under vacuum. Diethyl ethylmalonate is purified by fractional distillation in a wiped-film evaporator at 2–5 kPa oil temperature 90–110 °C. The clean intermediate is condensed with urea at a 1.00:1.05 molar ratio in ethanol containing 2.0–2.5 mol sodium ethoxide per mol substrate at 78–80 °C. The crude phenobarbital is crystallized from aqueous ethanol and centrifuged. Residual solvent control for the API follows ICH Q3C; methylene chloride is avoided in this sequence because its Class 2 concentration limit complicates the solvent recovery train.
Malonic acid is manufactured from diethyl malonate by saponification followed by acidification. The ester is charged into a jacketed glass-lined vessel containing 25–50 wt% aqueous sodium hydroxide at 60–75 °C. Addition is controlled by the ethanol evolution rate and condenser load. After hydrolysis, the batch is cooled to 20–30 °C and acidified with 30–35 wt% hydrochloric acid to pH 1.0–1.5. Malonic acid precipitates as white crystals. The slurry is cooled to 5–10 °C and filtered on a pressure Nutsche. The filtrate contains sodium chloride and residual ethanol; ethanol is recovered by rectification to reduce wastewater chemical oxygen demand. Vacuum drying is performed below 60 °C because malonic acid decarboxylates at 132 °C to acetic acid and carbon dioxide. The dried product is tested by acid-base titration and loss on drying per USP <731>. Terminal uses include barbituric acid production, 1,3-propanediol via ester hydrogenation, and polyester monomers. The operational boundary is that distillation or drying above 60 °C can lower assay and generate acetic acid; therefore vacuum dryers with heated shelves are set to 40–50 °C under 10–15 kPa.
When protected amino acid syntheses require a hydrolytically stable active methylene carrier, diethyl acetamidomalonate is prepared from diethyl malonate by nitrosation and zinc reduction. A solution of diethyl malonate in acetic acid is treated with aqueous sodium nitrite at 0–5 °C. The intermediate diethyl oximinomalonate is extracted into ethyl acetate, washed with brine, and concentrated. The oxime is reduced with zinc dust in the presence of acetic anhydride at 0–10 °C; the reduction is strongly exothermic and evolves hydrogen, so the reactor is inerted with nitrogen and the condenser is vented through a flame arrestor. Diethyl acetamidomalonate is isolated by vacuum distillation and stored under nitrogen. Alkylation with benzyl chloride or 2-iodopropane is performed in sodium ethoxide solution, followed by hydrolysis with 6 M hydrochloric acid and neutralization to the isoelectric point. The route yields racemic amino acids such as D,L-phenylalanine and D,L-leucine. Chiral purity is not achieved without resolution; the racemate is either resolved via diastereomeric salt formation or subjected to enzymatic kinetic resolution. The operational boundary is that the zinc reduction must be kept below 10 °C because uncontrolled exotherm increases hydrogen evolution rate and can entrain acetic anhydride vapor into the vent system.
Malonate-functional oligomers are synthesized by transesterification of diethyl malonate with trimethylolpropane or neopentyl glycol in a stainless-steel reactor at 140–160 °C under nitrogen with 20 kPa vacuum. Dibutyltin oxide is used at 0.05–0.10 wt% based on reactor charge. Ethanol is stripped until the acid number falls below 5 mg KOH/g by ASTM D664, and nonvolatile content exceeds 98 wt% by ISO 3251:2019. The resin is cooled to 30 °C and blended with trimethylolpropane triacrylate at an acrylate-to-malonate molar ratio of 1.0:1.0 to 1.3:1.0. Cure is initiated with 1,8-diazabicyclo[5.4.0]undec-7-ene at 0.5–1.5 wt%. Pot life is measured on a cone-and-plate viscometer at 25 °C. Gelation is defined by the crossover of storage modulus and loss modulus in small-amplitude oscillatory shear at 10 rad/s and 1 % strain per ASTM D4440-15. Films are drawn with a wire-wound bar to 20–40 µm wet film on phosphate-treated cold-rolled steel panels. Cured coatings are evaluated by methyl ethyl ketone double rubs per ASTM D5402-19, pencil hardness per ASTM D3363-20, and cross-cut adhesion per ISO 2409:2020. The chemistry is used in high-solids coil primers and industrial maintenance topcoats where low volatile organic compound content and ambient cure are required. The operational boundary is that primary amine accelerators, amine-functional wetting agents, or amine-bearing pigments trigger premature Michael addition and reduce pot life below the minimum required for spray line charging. Free malonate content is also controlled because unreacted diethyl malonate acts as a volatile plasticizer and delays cure. The cured film exhibits solvent resistance only when the acrylate-to-malonate stoichiometry is maintained above 1.0:1.0; below that ratio, unconverted malonate groups remain and the film remains solvent-sensitive.
The following analytical control matrix applies to diethyl malonate and its downstream malonate-functional intermediates:
| Parameter | Method/Standard | Control Objective |
|---|---|---|
| Water content in diethyl malonate | ASTM E203 | < 0.10 wt% |
| Diethyl malonate purity | GC-FID internal standard | > 99.0 area% |
| Acid number of malonate-functional resin | ASTM D664 | < 5 mg KOH/g |
| Nonvolatile content | ISO 3251:2019 | > 98 wt% |
| Cured coating solvent resistance | ASTM D5402-19 | report MEK double rubs |
| Adhesion | ISO 2409:2020 | report cross-cut class |
For high-voltage lithium-ion cells, laboratory coin-cell evaluations of diethyl malonate as a film-forming additive are conducted with baseline 1.0 M LiPF6 in ethylene carbonate/dimethyl carbonate at a volume ratio of 1:1. Diethyl malonate is blended at 0.5–2.0 wt% inside a glovebox with water and oxygen below 1 ppm. Electrolyte viscosity and conductivity are recorded at 25 °C before assembly. Half cells use LiNi0.6Mn0.2Co0.2O2 or LiFePO4 working electrodes, lithium metal foil counter electrodes, and polyethylene or polypropylene separators. Formation cycling is performed at 0.1 C between 3.0 V and 4.3 V, followed by 1 C cycling at 25 °C per IEC 62660-1:2018. Terminal products include electrolyte formulations for high-voltage lithium-ion pouch cells used in portable electronics and automotive traction batteries. Production-scale blending requires moisture-proof stainless-steel dosing lines and inline Karl Fischer control below 20 ppm. Published data for this specific configuration is limited; diethyl malonate performance depends on the positive electrode surface area, transition metal content, and formation protocol. The operational boundary is that diethyl malonate is not a drop-in substitute for vinylene carbonate; it must be screened together with fluoroethylene carbonate and propane sultone in the same anode/electrolyte system. Cells containing diethyl malonate require gas generation tests during formation because ester reduction can release carbonate decomposition products.
A continuous tubular reactor is packed with copper chromite or CuO/ZnO/Al2O3 extrudates and heated to 160–200 °C under hydrogen pressure of 8–15 MPa. Diethyl malonate is fed as a 10–30 wt% solution in tetrahydrofuran or dioxane to maintain single-phase flow. The ester groups are reduced to 1,3-propanediol; by-products including n-propanol, ethyl propionate, and methane are controlled by the hydrogen-to-ester ratio and contact time. Conversion is monitored by gas chromatography with thermal conductivity detection. 1,3-Propanediol is purified by vacuum distillation and ion-exchange treatment. This route is process-limited by the competing hydrogenolysis of the primary alcohol intermediate; increasing temperature above 200 °C raises alkane by-product selectivity. Published data for industrial-scale production of 1,3-propanediol by direct diethyl malonate hydrogenation is limited; the established commercial routes are ethylene oxide hydroformylation and glucose fermentation. The terminal product is used for polytrimethylene terephthalate and personal care humectants. Purity is confirmed by gas chromatography and water content by ASTM E203. The operational boundary is that the hydrogenation catalyst deactivates in the presence of sulfur impurities, so diethyl malonate feed is pretreated by adsorption over activated alumina or molecular sieves to maintain sulfur below 5 ppm.
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Diethyl malonate (CAS 105-53-3; C₇H₁₂O₄; molar mass 160.17 g/mol) is supplied as a clear, colourless ester-liquid with a characteristic fruity odour and a C₃ dicarboxylic acid equivalent function. It is used as an active methylene synthon in condensation, alkylation, cycloaddition, and transesterification chemistries. Industrial release specifications are typically set around assay (GC) ≥99.0%, water by ASTM E203 ≤0.10%, acidity as malonic acid ≤0.10%, refractive index n²⁰/D 1.413–1.415, density at 20 °C 1.055–1.058 g/cm³ by ASTM D4052, and boiling range 197–199 °C at 760 mmHg by ASTM D1078. The flash point determined by ASTM D93 closed cup is 93 °C. Bulk packaging is commonly 200 L epoxy-phenolic lined steel drums or stainless steel ISO tank containers; a nitrogen blanket is maintained when downstream processing is moisture-sensitive.
| Parameter | Method | Typical release limit |
|---|---|---|
| Assay, gas chromatography | Internal standard method | ≥99.0% |
| Moisture | ASTM E203 | ≤0.10% |
| Acidity as malonic acid | Alcoholic potassium hydroxide titration | ≤0.10% |
| Refractive index n²⁰/D | ASTM D1218 | 1.413–1.415 |
| Density at 20 °C | ASTM D4052 | 1.055–1.058 g/cm³ |
| Boiling range | ASTM D1078 | 197–199 °C |
| Flash point, closed cup | ASTM D93 | 93 °C |
Technical grades with assay 98.0% are available for agrochemical intermediates, while pharmaceutical syntheses generally specify ≥99.5% assay and individual impurity control for monoethyl malonate and diethyl carbonate at ≤0.10% each. Distinction between grades is made by assay, residual acid, and moisture level rather than by model number; supplier product codes typically encode purity grade and packaging configuration.
When a reaction sequence requires a higher boiling point and easier organic-phase recovery, diethyl malonate is generally selected over dimethyl malonate. Diethyl malonate boils at 199 °C, whereas dimethyl malonate boils at 181 °C; this difference extends the compatible operating envelope in toluene or xylene azeotropic drying systems and reduces distillate losses when high-vacuum stripping is unavailable. The ethyl ester is less polar and partitions more strongly into non-polar solvents, which reduces hydrolysis losses during aqueous work-up. Against malonic acid, diethyl malonate offers a liquid transfer and metering advantage because its melting point is below -50 °C, and it does not require pre-dissolution in water or polar solvents that must later be removed. The penalty is that the two ethyl groups increase steric demand during enolate alkylation; preparative studies often use slow addition of the electrophile and a slight excess of the malonate anion to hold dialkylation below 1.0 area% by GC. Dimethyl malonate may be preferred when methanol removal is more compatible with downstream polymerization processes, but published rate-constant comparisons for identical alkyl halide/substrate combinations are limited and should be generated before process lock.
Against ethyl acetoacetate, diethyl malonate presents two equivalent ester carbonyls rather than a ketone-ester couple, so the α-carbon is less acidic but the derived anion is less stabilized by enolate delocalization. The aqueous pKa of diethyl malonate is approximately 13.3, while ethyl acetoacetate has a pKa near 10.7; consequently, diethyl malonate requires stronger anhydrous alkoxide bases and is less prone to self-condensation. This difference is exploited when a clean monocarbonyl homologation is desired, because the malonate route can deliver a substituted acetic acid after hydrolysis and decarboxylation without ketone cleavage side reactions. Ethyl acetoacetate remains more suitable when the acetoacetate dianion or Claisen condensation behaviour is required directly.
Pharmaceutical routes consume diethyl malonate as the malonate donor in barbiturate ring formation and as a precursor to monoethyl malonate after selective hydrolysis. Condensation with urea under sodium ethoxide catalysis yields barbituric acid derivatives; subsequent C5 alkylation generates the substituted intermediates common to sedative-hypnotic and anticonvulsant scaffold synthesis. Certain vitamin B1 and B6 synthesis routes use the malonate unit for pyrimidine and thiazole building blocks, and because these processes operate at multi-ton scale, incoming moisture and acidity are controlled within narrow limits to avoid stoichiometric drift. Agrochemical processes consume the same C₃ fragment in the construction of herbicidal and fungicidal actives where the malonate supplies a β-dicarbonyl or cyclopropane precursor after alkylation and cyclization. In flavor and fragrance compounding, diethyl malonate is listed under FDA 21 CFR 172.515 as a synthetic flavoring substance and carries FEMA number 2375; its use in fruit and apple-type compositions is limited by good manufacturing practice rather than a fixed dosage, and typical applications are in the low parts-per-million range. The ester also serves as a building block in organic synthesis of substituted acetic acids via alkylation, hydrolysis, and decarboxylation, and in the preparation of 2-alkyl-1,3-propanediols used as polymer-chain extenders and plastic alcohol intermediates. High-purity material is required for pharmaceutical oral dosage syntheses; lower-purity technical grades are used in intermediates where distillation and crystallization separate downstream impurities.
Polymer and coating applications consume smaller volumes of diethyl malonate than pharmaceutical intermediates. The ester can be transesterified with polyols to form malonate polyester polyols for use in high-solids alkyd coatings and aminoplast crosslinked systems. Cure with melamine-formaldehyde resins is typically conducted at 130–150 °C; the malonate segment modifies crosslink density and film flexibility, although published formulation data for specific malonate-based coatings is limited. Acid value and hydroxyl number titration follow ASTM D4274 and ISO 2554. In lubricant additive synthesis, the malonate fragment can be alkylated to yield branched carboxylic acid intermediates for metal-salt detergents; performance qualification is application-specific and requires bench-scale friction and deposit testing before commercial adoption.
Storage stability is influenced by moisture ingress, alkaline residues, and prolonged exposure to carbon steel. Diethyl malonate is soluble in ethanol, diethyl ether, toluene, and most ketone solvents; its aqueous solubility is low, with supplier safety data sheets generally reporting values below 10 g/L at 20 °C. The flash point of 93 °C means the material is handled as a combustible liquid rather than a highly flammable solvent; closed transfer is still used because vapours can form ignitable mixtures near heated reactor heads. Materials of construction for storage tanks and transfer lines should be 316L stainless steel or glass-lined carbon steel; copper, copper alloys, and bare mild steel should be avoided where trace metal pickup can discolour the product. Prolonged contact with strong aqueous bases such as sodium hydroxide leads to saponification to sodium malonate and ethanol; therefore, alkaline washes should be conducted cold and short. Oxidizing agents, acid chlorides, and strong reducing agents should be segregated. When the product is stored outdoors in northern climates, heating and recirculation are required below -10 °C, and viscosity increases as temperature approaches the pour point; published data for exact pour-point values vary by supplier. For anhydrous downstream processing, pre-drying with molecular sieves type 4A is specified when storage relative humidity exceeds 60%.
Safety data sheets issued under REACH classify diethyl malonate as a combustible liquid and skin/eye irritant. Full risk management measures appear in Sections 7 and 13 of the extended SDS. Section 7 recommends storing containers tightly closed and grounded; Section 13 advises disposal by incineration at licensed facilities. The material is not listed under Annex VI of CLP as a carcinogen, mutagen, or reproductive toxicant, but repeated skin contact should be controlled with nitrile gloves and chemical-splash goggles meeting EN 166. Emergency showers and eyewash stations are required where bulk transfers are conducted.
At reactor scale, the condensation of diethyl malonate with electrophiles is typically performed in glass-lined reactors equipped with a reflux condenser and a nitrogen purge. For malonic ester alkylation, the enolate is generated by adding diethyl malonate to a stirred suspension of sodium ethoxide in anhydrous ethanol at 0–5 °C; the addition is exothermic and controlled to avoid thermal run-away. The resulting sodium diethyl malonate solution is then treated with the alkyl halide at 20–40 °C for primary iodides and bromides, while less reactive alkyl chlorides may require heating to 80–90 °C in ethanol under pressure. Agitation in a 4,000 L glass-lined vessel is typically maintained at 80–120 rpm with a retreat-curve impeller; insufficient agitation can produce localized alkyl halide pooling and bis-alkylation. The bis-alkylation impurity can be held below 1.0 area% by maintaining a slight molar excess of the sodium malonate and by slow alkyl halide addition. After reaction, the product is quenched into dilute acetic acid, extracted with toluene, and distilled under vacuum to remove unreacted diethyl malonate; typical distillation of the monoalkylated product uses a wiped-film evaporator or batch rectification at pressures between 10–50 mbar. Published data for continuous-flow variants is limited, but microreactor studies indicate improved heat-transfer control for the deprotonation step relative to batch reactors. The same equipment can be used for transesterification processes where diethyl malonate is reacted with higher alcohols in the presence of a tin or titanium catalyst; ethanol removal shifts the equilibrium, and residual catalyst is quenched with aqueous acid before distillation. In such systems, residual moisture above 0.10% negatively affects catalyst activity and accelerates hydrolysis to monoethyl malonate, which distills in a higher-boiling fraction and reduces overall yield.
