| HS Code | 935616 |
| Product Name | Dimethyl Malonate |
| Synonyms | Dimethyl propanedioate; Malonic acid dimethyl ester; DMM |
| Cas Number | 108-59-8 |
| Einecs Number | 203-597-1 |
| Molecular Formula | C5H8O4 |
| Molecular Weight | 132.12 g/mol |
| Appearance | Colorless clear liquid |
| Odor | Ester-like, fruity |
| Density | 1.154 g/mL at 25 °C |
| Melting Point | -62 °C |
| Boiling Point | 181 °C at 760 mmHg |
| Flash Point | 76.7 °C (170 °F) closed cup |
| Refractive Index | n20/D 1.413 |
| Solubility | Soluble in water and common organic solvents such as alcohols and ethers |
| Vapor Density | 4.56 (air = 1) |
| Storage Conditions | Store in a cool, dry, well-ventilated area away from moisture and ignition sources |
| Purity | ≥99% (typical commercial grade) |
As an accredited Dimethyl Malonate factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Dimethyl malonate supplied in 1 L amber glass bottle with chemical-resistant cap, sealed for safe laboratory handling and storage. |
| Container Loading (20′ FCL) | 20′ FCL container loading of Dimethyl Malonate: sealed drums, palletized, evenly distributed, securely braced, and container sealed for export. |
| Shipping | Dimethyl malonate is generally not regulated for transport by DOT/IMDG/IATA in non-bulk quantities. Ship in tightly closed, upright containers, protected from heat, ignition sources, and oxidizers. Keep cool, dry, and well-ventilated. For bulk shipments, verify combustible-liquid rules and applicable local/international regulations. |
| Storage | Store Dimethyl Malonate in a cool, dry, well-ventilated area away from heat, sparks, flames, and direct sunlight. Keep containers tightly closed, upright, and labeled. Separate from strong oxidizers, acids, and bases. Use grounded, compatible containers and avoid moisture. Maintain emergency spill and fire equipment nearby. Follow local regulations and SDS recommendations. Store in original packaging, in a flammable-liquids cabinet if required. |
| Shelf Life | Dimethyl malonate typically has a two-year shelf life if kept sealed, cool, dry, and protected from moisture and contaminants. |
Representative commercial dimethyl malonate release specification is assay ≥99.0% by gas chromatography per USP <621>, water ≤0.10% by Karl Fischer per ASTM E203-23, acid value ≤1.0 mg KOH/g per ASTM D1613-17, and appearance as a clear liquid. Dimethyl malonate is condensed with aromatic aldehydes in a jacketed glass-lined reactor under azeotropic water removal. A representative charge ratio of dimethyl malonate to benzaldehyde is 1.0–1.2 mol/mol, with piperidine acetate at 0.05–0.10 mol/mol dimethyl malonate in toluene at 70–80 °C. Water is removed through a Dean-Stark trap until gas chromatography per USP <621> indicates residual aldehyde below 0.5%. The downstream production sequence includes phase separation of the organic layer, washing with 5% sodium bicarbonate solution, vacuum distillation at 2–5 kPa, and final crystallization from methanol/water. Terminal finished product types derived from this pathway include benzylidene malonate and subsequent cinnamate esters used in fruit, spice, and balsamic fragrance compositions. Compliance for fragrance substances placed on the EU market falls under Regulation (EC) No 1334/2008, while the final formulated fragrance mixture is subject to IFRA Standards as amended; if the resulting flavour substance is listed in 21 CFR 172.515, the finished flavour must also meet USP <921> water content and residual methanol limits under USP <467>. Operational boundaries observed on pilot-scale equipment: addition of aldehyde is controlled to maintain reaction mass temperature below 80 °C. Above 85 °C the rate of Michael addition oligomerisation rises sharply, indicated by an increase in high-boiling residue to over 2.0% and a drop in isolated yield to below 90%. Dimethyl malonate combined with strong aqueous caustic prior to ester hydrolysis is avoided when free aldehyde is still present because aldol condensation byproducts co-distil with the target intermediate.
Sodium methoxide in methanol is used rather than sodium ethoxide in ethanol when dimethyl malonate is selected, because transesterification to mixed ethyl-methyl malonates is eliminated. In active pharmaceutical ingredient intermediate production, a representative molar ratio is dimethyl malonate to alkylating agent 1:1.05–1:1.20, with 1.05–1.10 mol sodium methoxide per mol dimethyl malonate. The reactor is charged with 25–30 wt% sodium methoxide in methanol, heated to 60–65 °C, and the alkyl halide is metered over 2–4 h. After conversion by gas chromatography per USP <621> exceeds 98.0%, the batch is cooled, quenched into dilute hydrochloric acid at 0–5 °C, extracted, and the substituted dimethyl malonate is either distilled or directly hydrolysed. This process falls under ICH Q7, Section 8 for production and in-process controls, when the material is an active pharmaceutical ingredient intermediate; if the product enters a US finished drug, 21 CFR Part 210 and Part 211 apply to subsequent formulation steps. Analytical controls include moisture by USP <921>, residual alkyl halide by headspace gas chromatography per USP <467>, and residue on ignition by USP <281>. Terminal finished product types include monosubstituted malonic acids used in arylacetic acid nonsteroidal anti-inflammatory building block synthesis, arylethylamine intermediates, and precursors for anticonvulsant active pharmaceutical ingredients. Batch-to-batch variance on a 2000 L glass-lined reactor is most influenced by alkyl halide feed rate: feed rates above 0.8 kg/min have produced temperature excursions above 68 °C, leading to dialkylated malonate impurity above 3.5% and requiring redistillation. Pre-drying of methanol to below 0.10% water is required because water hydrolyses sodium methoxide and shifts the deprotonation equilibrium, reducing monosubstitution selectivity.
| Downstream pathway | Governing standard/code | Analytical reference | Critical operational limit |
|---|---|---|---|
| Flavour/fragrance Knoevenagel condensation | Regulation (EC) No 1334/2008; IFRA Standards; 21 CFR 172.515 for listed final substances | USP <621>; USP <467> | Reaction mass ≤ 80 °C; residual aldehyde ≤ 0.5% |
| Pharmaceutical malonic ester alkylation | ICH Q7, Section 8; 21 CFR Part 210 and Part 211 | USP <621>; USP <921>; USP <467> | Alkyl halide feed ≤ 0.8 kg/min; batch temperature ≤ 65 °C |
| Crop protection heterocyclic intermediate | Regulation (EC) No 1107/2009; REACH Regulation (EC) No 1907/2006 | CIPAC Handbook methods; USP <621> | Cyclisation temperature 65–75 °C; hydrazine concentration ≤80% |
| Barbituric acid condensation | ICH Q7, Section 8; USP <621> | USP <621>; USP <281>; USP <467> | Reaction temperature 70–75 °C; pH endpoint 1.0–1.5 |
| Malonic acid saponification | REACH Regulation (EC) No 1907/2006; ISO 9001:2015 | ASTM E203-23; USP <621> | Saponification pH 12.5–13.0; acidification pH 1.2–1.8 |
Crop protection intermediate synthesis consumes dimethyl malonate as a 1,3-dicarbonyl building block for pyrazole and pyrimidine cores that are subsequently chlorinated, sulfonated, or carboxylated. Representative addition ratio is dimethyl malonate to substituted hydrazine 1:1.0–1.05 mol/mol; the reaction is run in methanol at 65–75 °C with 0.05–0.10 mol acetic acid per mol dimethyl malonate as cyclisation promoter. Downstream production processes include neutralisation with sodium bicarbonate, vacuum distillation of the intermediate ester, and optional hydrolysis to the pyrazole carboxylic acid using 10–15 wt% sodium hydroxide at 85–90 °C for 4–6 h. Finished product types from this route are carboxylic acid intermediates and heterocyclic esters used in herbicide and fungicide active ingredient synthesis. Compliance for active substances in the EU falls under Regulation (EC) No 1107/2009; technical-grade intermediates imported into the EU must meet REACH Regulation (EC) No 1907/2006 Annex XVII restrictions where applicable. Analytical release of the downstream intermediate commonly references CIPAC Handbook methods for moisture and gas chromatographic purity; commercial dimethyl malonate suppliers typically specify purity above 99.0% by gas chromatography per USP <621>, water below 0.10% by Karl Fischer per ASTM E203-23, and acid value below 1.0 mg KOH/g per ASTM D1613-17. A process conflict arises with hydrazine hydrate above 80% concentration: a sharp exotherm occurs and heterocycle selectivity can decrease to below 85% because of pyrazolidine ring opening. Published data for specific proprietary herbicide active ingredients derived from this building block is limited, so laboratory validation per CIPAC and OECD 503 is required before scale-up.
The synthesis of barbituric acid from dimethyl malonate and urea in sodium methoxide is exothermic and requires simultaneous removal of methanol to shift equilibrium toward ring closure. A representative molar ratio is dimethyl malonate to urea 1:1.0–1.05, with sodium methoxide 1.0–1.1 mol/mol dimethyl malonate. The reaction mass is heated to 70–75 °C; methanol is distilled at 65–75 °C under atmospheric pressure, and reactor pressure is monitored below 0.5 bar(g) during methanol vapour venting. After 3–5 h, the mixture is cooled to 20–25 °C, quenched into water, and acidified with 30–35% hydrochloric acid to pH 1.0–1.5; the precipitated barbituric acid is filtered, washed, and dried at 60–70 °C under vacuum. This sequence is governed by ICH Q7, Section 8, when the material is an intermediate for an active pharmaceutical ingredient; the dried barbituric acid is tested for chromatographic purity per USP <621>, residue on ignition per USP <281>, and residual methanol per USP <467>. Terminal finished product types include barbiturate active pharmaceutical ingredients and their sodium salts for sedation and anaesthesia; barbituric acid itself is also converted into dyes and pharmaceutical intermediates. The critical processing window is ±5 °C: at reaction temperatures below 65 °C conversion stalls below 90%, while above 80 °C urea decomposition releases ammonia and raises reactor pressure, producing amide impurities. On a 1000 L reactor, the exotherm can reach 150–200 W/kg during the first hour; jacket cooling water at 5–10 °C and controlled methanol reflux are required.
Saponification of dimethyl malonate to malonic acid is carried out in a cooled stainless-steel reactor with controlled sodium hydroxide addition. Representative addition ratio is dimethyl malonate to sodium hydroxide 1:2.05–2.20 mol/mol, with water charged at 1.5–2.0 L/kg dimethyl malonate; saponification proceeds at 80–90 °C for 2–3 h. Methanol is stripped from the reactor at atmospheric pressure before acidification with 30% hydrochloric acid to pH 1.2–1.8. The crude malonic acid is crystallised by cooling, centrifuged, and dried under vacuum at 60–70 °C. Terminal finished product types include technical-grade malonic acid, disodium malonate, and malonyl chloride produced by subsequent reaction with thionyl chloride at 2.1–2.3 mol/mol malonic acid in dichloroethane at 50–60 °C; these materials are consumed in chemical synthesis, electroplating bath additives, and pharmaceutical intermediate production. Compliance for industrial-grade malonic acid falls under REACH Regulation (EC) No 1907/2006 and ISO 9001:2015; analytical release includes assay by USP <621>, water by ASTM E203-23, and chloride content by titration. Austenitic stainless steel 316L crystallisers are susceptible to chloride stress-corrosion cracking if hydrochloric acid is introduced above 70 °C; glass-lined or rubber-lined crystallisers are specified when acidification and crystallisation are conducted in the same vessel. Methanol recovery from the saponification step requires rectification to below 0.10% water before reuse, because wet methanol reduces sodium hydroxide activity in the next batch and lowers isolated malonic acid yield to below 88%.
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As a low-molecular-weight aliphatic diester, dimethyl malonate (CAS 108-59-8; IUPAC name dimethyl propanedioate; linear formula CH2(COOCH3)2) is supplied as a liquid raw material for condensation, alkylation, and transesterification processes. The molecular weight is 132.11 g/mol, the atmospheric boiling point is 180–181 °C, the melting point is −62 °C, and the density is 1.156 g/mL at 25 °C. The refractive index at 20 °C is 1.4135, and the closed-cup flash point is 90 °C. Under normal warehouse conditions the product is a low-viscosity liquid that remains pumpable at ambient temperature. Commercial supply is separated into standard technical grade, low-water grade, and high-purity grade. Supplier-specific grade codes may include DMM-ST, DMM-LW, and DMM-HP, where the designation indicates standard technical, low-water, or high-purity control. These grades are differentiated by assay, water content, acidity, and color rather than by a single universal product code; purchasing specifications should therefore reference the downstream reaction step. Bulk packaging is typically 200 kg HDPE drums or 1,000 kg stainless steel IBCs with nitrogen blanketing.
Release analysis for dimethyl malonate is performed on a batch basis against a certificate of analysis that includes assay, water, acidity, color, distillation range, and density. The assay is determined by capillary gas chromatography with flame ionization detection using an internal standard; this procedure is controlled under the supplier’s ISO 9001:2015 quality plan. Water is measured by volumetric Karl Fischer titration according to ASTM E203. Acidity is expressed as malonic acid and determined by non-aqueous titration. Distillation range is measured according to ASTM D1078, density by ASTM D4052, and color by the platinum-cobalt scale under ASTM D1209. The table below shows representative specification limits for standard technical and low-water material.
| Parameter | Test method | Standard technical grade | Low-water grade |
|---|---|---|---|
| Assay, total esters | Capillary GC | ≥99.0% | ≥99.5% |
| Water | ASTM E203 | ≤0.10 wt% | ≤0.05 wt% |
| Acidity as malonic acid | Acid-base titration | ≤0.10 wt% | ≤0.05 wt% |
| Color, Pt-Co | ASTM D1209 | ≤15 | ≤10 |
| Distillation range | ASTM D1078 | 179–182 °C | 180–181.5 °C |
| Density at 20 °C | ASTM D4052 | 1.150–1.160 g/cm³ | 1.153–1.156 g/cm³ |
For high-purity pharmaceutical intermediate use, buyers frequently add a chloride residue limit, a sulfate ash limit, and a residual solvent profile by headspace GC. The low-water grade is recommended when dimethyl malonate will be introduced into a reaction containing alkoxide bases or titanium-based transesterification catalysts, because water at 0.10 wt% or above can consume catalyst and reduce conversion.
Industrial production of dimethyl malonate follows either the esterification of malonic acid with methanol or the carbonylation of methyl chloroacetate in methanol. In the esterification route, a glass-lined batch reactor equipped with a distillation column and a phase separator processes malonic acid and excess methanol in the presence of an acid catalyst. The reaction is equilibrium-limited; water removal is the primary driver of conversion. The overhead temperature of 64–65 °C corresponds to the methanol/water azeotrope at atmospheric pressure, and the reflux ratio is adjusted between 1:1 and 3:1 to keep residual water below 0.50 wt% before neutralization. After esterification, the crude mixture is washed with aqueous sodium bicarbonate to reduce monomethyl malonate and malonic acid acidity. The organic phase is then dried and distilled through a packed column. The heart cut is collected at 180–181 °C and typically exceeds 99.0% assay by GC. In the carbonylation route, methyl chloroacetate and methanol are reacted with carbon monoxide in the presence of a cobalt carbonyl catalyst. This route offers a shorter sequence from chloroacetic acid but requires post-reaction chloride removal and catalyst recovery. Plant experience shows that chloride-containing recycle streams accelerate corrosion in carbon steel overheads; therefore, the distillation train for carbonylation-derived material is specified in glass-lined or high-alloy stainless steel. Batch-to-batch variance in color is controlled by nitrogen sparging during distillation and by avoiding sustained hold times above 120 °C in the reboiler.
Because the closed-cup flash point is 90 °C when measured by ASTM D93, dimethyl malonate is classified as a combustible liquid under GHS, and storage areas are typically separated from oxidizers according to local fire code. Drums and IBCs should be stored at 15–30 °C under nitrogen or dry air. Shelf life in unopened containers is normally stated as 24 months from the date of manufacture when the product is not exposed to repeated moisture ingress. The primary stability boundary is water. Hydrolysis to monomethyl malonate and malonic acid is slow at neutral pH but accelerates when the product is heated above 50 °C with free water, or when residual acidity is elevated. In drums opened at relative humidity above 60%, the material should be dried with 3A molecular sieves or re-tested for water before use in anhydrous processes. Contact with strong bases such as sodium methoxide is an intentional reaction pathway but is exothermic; uncontrolled addition of concentrated alkali can generate methanol and the corresponding malonate salt, and the heat release should be removed by jacket cooling. Primary amines and strong oxidizing agents are incompatible in storage and in multi-use transfer lines because slow aminolysis or oxidation can produce colored byproducts and off-specification material. If the product is transferred through carbon steel lines, the lines should be dried and purged after use to prevent rust particle contamination; stainless steel or HDPE transfer equipment is preferred.
Substitution of dimethyl malonate for diethyl malonate changes the solvent recovery limit, the alkoxide base required, and the thermal window available for high-temperature alkylation. Dimethyl malonate boils at 180–181 °C, while diethyl malonate boils at 198–199 °C; this 18–19 °C difference reduces reboiler energy in solvent distillation but also lowers the maximum reaction temperature in atmospheric systems. Dimethyl malonate is typically deprotonated with sodium methoxide in methanol, whereas diethyl malonate is commonly deprotonated with sodium ethoxide in ethanol. The active methylene pKa of dimethyl malonate is approximately 13.0; the corresponding diethyl malonate value is approximately 13.3. The stronger acidity of the dimethyl ester gives a slightly higher enolate concentration at the same base charge, but it also increases sensitivity to over-alkylation and dialkylation. In malonic ester synthesis, the methyl ester byproduct is methanol, which can be stripped more easily than ethanol at low overhead temperatures; however, the handling system must be rated for methanol’s lower flash point. For buyers that require a higher-boiling malonate to remain in the reaction mixture during distillative removal of water or solvent, diethyl malonate may be preferred. The comparative physical properties relevant to solvent replacement decisions are given below.
| Property | Dimethyl malonate | Diethyl malonate | Malonic acid |
|---|---|---|---|
| CAS number | 108-59-8 | 105-53-3 | 141-82-2 |
| Molecular weight | 132.11 g/mol | 160.17 g/mol | 104.06 g/mol |
| Boiling point | 180–181 °C | 198–199 °C | Decomposes |
| Melting point | −62 °C | −51 °C | 135–137 °C (dec.) |
| Density at 25 °C | 1.156 g/mL | 1.055 g/mL | 1.619 g/cm³ solid |
| Refractive index n20/D | 1.4135 | 1.4139 | Not applicable |
| Closed-cup flash point | 90 °C | 93 °C | Not applicable |
Compared with malonic acid, the dimethyl ester is a distillable liquid that can be stored and pumped at ambient temperature; malonic acid decomposes at its melting point and cannot be used directly in non-aqueous enolate chemistry without prior esterification. These differences make dimethyl malonate the preferred form when a low-viscosity, low-water, active methylene synthon is required.
In multi-purpose pharmaceutical and agrochemical plants, dimethyl malonate is charged to glass-lined reactors of 5,000–10,000 L as an active methylene building block. For barbituric acid manufacture, dimethyl malonate and urea are condensed in methanolic sodium methoxide; the reaction mass is typically maintained at 60–70 °C for several hours, then quenched with water and acidified. The condensation releases methanol, which is recovered by distillation before acidification. In agrochemical intermediate synthesis, dimethyl malonate undergoes Knoevenagel condensation with substituted benzaldehydes to yield arylidene malonates. A typical setup uses a reactor with a Dean-Stark trap or a drying column, toluene or cyclohexane as the azeotroping solvent, and a catalytic amount of piperidinium acetate. Conversion is monitored by GC; the water removal rate controls the end point. The resulting arylidene malonates are then reduced, cyclized, or hydrogenated depending on the target active ingredient. Compared with diethyl malonate, the dimethyl homologue produces a lower-boiling methanol-rich azeotrope, which can reduce distillation time in solvent-bound reaction workups but may require continuous vapor monitoring for methanol exposure. Residual methanol in isolated intermediates is controlled under ICH Q3C; when dimethyl malonate is used upstream of a drug substance, the final API must meet the methanol limit of 3,000 ppm if methanol is not removed below the reporting threshold.
The active methylene group in dimethyl malonate is less acidic than β-diketone and β-ketoester systems. Published pKa values place dimethyl malonate near 13.0, acetylacetone near 8.9, and ethyl acetoacetate near 10.7. This lower acidity requires a stronger base for complete enolate generation but prevents the uncontrolled self-condensation observed with more acidic carbonyl systems. In Knoevenagel condensations with aromatic aldehydes, the reaction is driven by water removal. With benzaldehyde in toluene using piperidinium acetate, preparative methods report conversion to dimethyl benzylidene malonate above 95% after azeotropic water separation; the exact end point depends on aldehyde substitution and catalyst ratio. The two ester groups in dimethyl malonate are chemically equivalent, which simplifies stoichiometric control in alkylation and hydrolysis; however, after mono-alkylation the remaining acidic proton is still available for a second alkylation, so over-alkylation is controlled by staged base addition and temperature. Process development laboratories typically begin with a base charge of 1.0–1.05 equivalents relative to dimethyl malonate, maintain the reaction temperature below 70 °C during initial alkylation, and add the alkylating agent over 2–4 h to avoid hot spots. When the reaction is transferred to a production batch reactor, jacket cooling capacity should be validated for the exotherm associated with sodium methoxide addition; a maximum feed rate is set so that the internal temperature does not exceed 65 °C during enolate formation. Published plant-scale kinetic data for these specific configurations are limited, so laboratory calorimetry is recommended before scaling exothermic additions.
Quality systems for dimethyl malonate shipments include UN-number documentation, REACH registration where applicable, and GHS safety data sheet statements for combustible liquid and skin irritation. Because esterification-grade material does not contain chlorine and is not a phthalate, RoHS phthalate restrictions and chlorinated-solvent controls do not apply. However, carbonylation-route material can leave trace organochlorine impurities; suppliers of high-purity material should provide a chloride certificate if the downstream application uses precious-metal hydrogenation catalysts, because trace chloride can poison platinum and palladium catalyst surfaces. Incoming quality control laboratories typically verify density by ASTM D4052 and water by ASTM E203 before charging a received drum to a GMP intermediate vessel. Material that fails water or acidity specifications is not reworked without distillation; off-specification material is either returned or redistilled through a wiped-film evaporator to restore assay and color.
