SCIENTIFIC REFERENCE · CAS 110-15-6
A four-carbon dicarboxylic acid. Understand its two acid dissociation steps, its role as a chemical building block, and the differences that matter when comparing related acids.
Succinic acid is butanedioic acid, the neutral compound with a carboxyl group at each end of a two-methylene chain. The carboxyl carbon atoms count toward its four-carbon total. It is achiral and has no cis/trans identity.
| Property | Reference |
|---|---|
| Chemical / IUPAC name | Succinic acid / butanedioic acid |
| CAS number | 110-15-6 |
| Formula / molecular weight | C₄H₆O₄ / 118.09 g/mol |
| Family / structure | Saturated aliphatic dicarboxylic acid / HOOC–CH₂–CH₂–COOH |
| Carbon atoms / carboxyl groups | 4 / 2 |
| Approximate pKa₁ / pKa₂ | 4.21 / 5.64 in water at 25 °C; thermodynamic reference, ionic strength I = 0 |
| Appearance / physical state | White crystals or crystalline powder; solid at 20 °C |
| Melting point | 184–186 °C, Sigma literature value; product specification ranges differ (see below) |
| Water solubility | About 83 g/L at 25 °C; reference value, not a guaranteed dissolution rate |
Sources: PubChem: succinic acid, CID 1110 (opens a new tab) · Goldberg, Kishore & Lennen (2002), thermodynamic ionization constants; citrate §7.22, succinate §7.57 (opens a new tab) · Sigma-Aldrich 398055: US product, specifications and safety listing (opens a new tab) · TCI America S0100: US product and method-specific specifications (opens a new tab)
Each –COOH group can donate a proton. Loss of the first gives hydrogensuccinate; loss of the second gives succinate, a dianion. A bottle of sodium succinate therefore is not the same chemical form or formula mass as a bottle of succinic acid.
Which form predominates depends on pH and the solution environment. “Succinate” in biochemistry usually refers to the ion rather than a neutral molecule of the free acid.
H₂Suc ⇌ H⁺ + HSuc⁻
pKa₁ ≈ 4.21
HSuc⁻ ⇌ H⁺ + Suc²⁻
pKa₂ ≈ 5.64
The carboxyl groups provide acid/base and ester-forming chemistry. The saturated carbon skeleton differs from fumaric acid’s alkene, while the spacing of the groups differs from malonic and adipic acids. Solid-state packing and hydrogen bonding also affect melting and dissolution; counting acid groups alone cannot predict solubility.
These pKa values describe two equilibria, not a single measured solution pH. Actual pH requires concentration, temperature and solution composition. At finite ionic strength, activity effects matter. The second dissociation removes a proton from an already negative ion; its higher pKa reflects the less favorable overall equilibrium, including electrostatic and statistical effects. It is not an assertion that the two ends of the neutral molecule are chemically different.
Sources: Goldberg, Kishore & Lennen (2002), thermodynamic ionization constants; citrate §7.22, succinate §7.57 (opens a new tab) · PubChem: succinic acid, CID 1110 (opens a new tab) · OpenStax Organic Chemistry §29.7: the citric acid cycle (opens a new tab)
| Property | Value / observation | How to interpret it |
|---|---|---|
| Molecular identity | C₄H₆O₄; 118.09 g/mol | Neutral free acid, not a succinate salt or an aqueous solution. |
| Appearance | White crystals / crystalline powder | Supplier description; the physical state is solid at 20 °C. |
| Melting behavior | Sigma: 184–186 °C (literature). TCI S0100: 185–189 °C (specification). | A literature range and a commercial acceptance range are not the same measurement. Do not average them. |
| Water solubility | 83.2 g/L at 25 °C (PubChem/HSDB, Yalkowsky 2003); 83 g/L at 25 °C (TCI/Sigma reference). | Rounded values agree here. The cited records do not establish a common experimental method or buffered pH. Dissolution speed is a separate question. |
| Acid dissociation | pKa₁ 4.207; pKa₂ 5.636 | NIST review selection: water, 298.15 K, I = 0, hypothetical ideal unit-molality standard state. |
| Alternate compiled pKa | 4.207 / 5.635 at 25 °C in PubChem’s Dean attribution | The final 0.001 in pKa₂ differs between reference selections. Both round to 5.64; no precision advantage is implied. |
| Heating / boiling data | No operating boiling point recommended here | Some catalogs list 235 °C without pressure or transformation detail. That is insufficient for process design; the Wako SDS warns of hazardous decomposition products on heating. |
Use a property reference to understand the substance and the actual product specification to accept a purchased lot. Neither replaces measurements in your formulation or process.
Sources: PubChem: succinic acid, CID 1110 (opens a new tab) · Goldberg, Kishore & Lennen (2002), thermodynamic ionization constants; citrate §7.22, succinate §7.57 (opens a new tab) · Sigma-Aldrich 398055: US product, specifications and safety listing (opens a new tab) · TCI America S0100: US product and method-specific specifications (opens a new tab) · Wako 19-0433: English Japan/JIS SDS, revision 16 February 2023 (opens a new tab)
Succinic acid is used as a reactant in synthesis and polyester production, and as a food flavor enhancer and pH-control ingredient under specific US conditions. Metabolic references generally concern succinate. These roles should be distinguished from claims about finished succinate polymers, salts or esters.
INTERMEDIATE / MONOMER
Direct esterification with 1,4-butanediol produces succinate oligomers on the route to poly(butylene succinate), or PBS. The free acid is a feedstock: the resulting polymer’s film or mechanical performance belongs to the polymer, not to succinic acid powder.
Sources: Park, Jun & Im (1998), direct esterification of succinic acid and 1,4-butanediol (opens a new tab)
DIRECT USE · REGULATED CONTEXT
US 21 CFR 184.1091 specifies flavor-enhancing and pH-control uses, the incorporated FCC specification, and GMP conditions. It lists maximum as-served levels of 0.084% in condiments/relishes and 0.0061% in meat products. This does not qualify an arbitrary reagent for food use.
Sources: 21 CFR 184.1091: succinic acid, US food-use conditions (opens a new tab)
BIOCHEMICAL SPECIES
Succinate is an intermediate of the citric acid cycle and is oxidized to fumarate by succinate dehydrogenase. A research experiment must specify the acid or salt, counterion, concentration and pH. A normal metabolic role is not evidence for a health benefit from consuming the free acid.
Sources: OpenStax Organic Chemistry §29.7: the citric acid cycle (opens a new tab)
RESEARCH / PROCESS DEVELOPMENT
A 2025 study investigated catalytic conversion of renewable succinic acid to 1,4-butanediol and subsequent PBS synthesis. It demonstrates a particular process under controlled conditions, not that every commercial succinic acid product is bio-based or that the process is universally economical.
For an industrial or specialty synthesis, define the actual transformation and impurity tolerance. Broad labels such as “pharmaceutical,” “cosmetic,” or “plasticizer” do not establish direct use of the free acid or suitability of a particular grade.
Turning an application into a specification? The buying guide separates grade, assay method, documentation and purchasing requirements.
Start with the molecular difference, then examine the evidence that applies to your task. Sharing two carboxyl groups does not make two acids interchangeable. The comparisons below concern the free acids; salts, esters and hydrates need their own specifications.
01 · ONE FEWER CARBON
Structure: malonic acid has one –CH₂– between its carboxyl groups; succinic acid has two. Their molecular weights are 104.06 and 118.09 g/mol respectively, so equal masses also contain different numbers of molecules.
Acidity: thermodynamic aqueous values at 25 °C are 2.852 / 5.697 for malonic acid and 4.207 / 5.636 for succinic acid. Malonic acid has the more favorable first dissociation; the second values are much closer. This is not a ranking of solution pH at arbitrary concentrations.
Reactivity and use: malonic ester synthesis exploits a methylene between two ester carbonyls, followed by hydrolysis and decarboxylation. That is derivative chemistry, not a reason to substitute free malonic acid into a succinic-acid polyester recipe. Succinic acid’s two-methylene spacer defines a different monomer.
Solubility decision: the retrieved malonic records disagree even around 20–25 °C. A reliable numerical solubility ratio is not established here; confirm a condition-matched source or measure the intended system. Choose according to the required reaction and chemical form, not the similar names.
Explore Malonic Acid comparisons →Sources: Kettler, Wesolowski & Palmer (1992), malonic acid dissociation (opens a new tab) · PubChem: malonic acid, CID 867; attributed solubility records (opens a new tab) · Goldberg, Kishore & Lennen (2002), thermodynamic ionization constants; citrate §7.22, succinate §7.57 (opens a new tab) · OpenStax Organic Chemistry §22.7: malonic ester synthesis (opens a new tab) · Park, Jun & Im (1998), direct esterification of succinic acid and 1,4-butanediol (opens a new tab)
02 · A LONGER SATURATED CHAIN
Structure: adipic acid has six carbons and four methylene groups, compared with succinic acid’s four carbons and two methylenes. Its molecular weight is 146.14 g/mol.
Physical properties: TCI lists an adipic reference melting point of 153 °C and water solubility of 22 g/L at 20 °C. Succinic reference melting ranges are around 185 °C; its cited 83 g/L solubility is at 25 °C. The different temperatures preclude a precise solubility ratio.
Acidity: the IUPAC compilation quoted by PubChem gives adipic pKa values of 4.44 / 5.44 at 25 °C, with ionic strength unstated in the extracted entry. Other compilations differ slightly. Treat the values as reference context rather than a precisely matched thermodynamic comparison.
Materials choice: adipic acid with 1,6-hexanediamine is the classic nylon 66 monomer pair; succinic acid with 1,4-butanediol forms a succinate polyester. Changing the acid changes repeat-unit spacing and the product specification. Follow the validated polymer recipe and requalify a proposed substitution.
Explore Adipic Acid →Sources: PubChem: adipic acid, CID 196; IUPAC and Dean pKa compilations (opens a new tab) · TCI A0161: adipic acid reference properties (opens a new tab) · OpenStax Organic Chemistry §31.4: step-growth polymers (opens a new tab) · Park, Jun & Im (1998), direct esterification of succinic acid and 1,4-butanediol (opens a new tab)
03 · SATURATED VS. TRANS ALKENE
Structure: both have four carbons and two carboxyl groups, but fumaric acid is (E)-but-2-enedioic acid, with a carbon–carbon double bond. It is the trans isomer, not a saturated chain-length variant. Its 116.07 g/mol molecular weight reflects two fewer hydrogens.
Acidity and dissolution: the Merck values in PubChem are 3.03 / 4.54 at 25 °C; CRC instead reports 3.03 / 4.44 at 18 °C. Do not mix the temperatures or attribute the entire difference solely to temperature without the underlying measurements. TCI lists 6.3 g/L water solubility at 25 °C, much below its 83 g/L succinic reference at the same temperature. Those references still omit method and solution pH, so no exact performance ratio is inferred.
Application choice: fumaric acid’s C=C bond enables chemistry absent from saturated succinic acid. Its own US food regulation covers specific acidulant uses. Choose the structure, regulatory basis and dissolution behavior required by the formulation; neither acidity nor food-use status establishes a drop-in replacement.
Explore Fumaric Acid →Sources: PubChem: fumaric acid, CID 444972; Merck and CRC pKa references (opens a new tab) · TCI F0067: fumaric acid reference properties (opens a new tab) · TCI America S0100: US product and method-specific specifications (opens a new tab) · 21 CFR 172.350: fumaric acid and salts, US food-use conditions (opens a new tab)
04 · TWO ACID GROUPS VS. THREE
Citric acid has three carboxyl groups and one additional alcohol group. The anhydrous acid is C₆H₈O₇, 192.12 g/mol; citric acid monohydrate includes crystal water and is not that same mass basis. Its three aqueous dissociation steps have thermodynamic pKa values of 3.128 / 4.761 / 6.396 at 25 °C.
Its solubility record includes 59.2% by mass at 20 °C, which cannot be compared directly with succinic acid’s g/L at 25 °C. A concentration basis, density and matched temperature would be needed for conversion and comparison.
For a pH-control application, select the acid/base system around the target pH and required buffer capacity, then validate concentration, other ingredients and product requirements. Citric and succinic acids also have different US food provisions. Neither the extra acid group nor a familiar food use makes them interchangeable gram for gram.
Explore Citric Acid →Sources: PubChem: citric acid, CID 311; solubility bases differ (opens a new tab) · Goldberg, Kishore & Lennen (2002), thermodynamic ionization constants; citrate §7.22, succinate §7.57 (opens a new tab) · 21 CFR 184.1033: citric acid, US food-use conditions (opens a new tab) · 21 CFR 184.1091: succinic acid, US food-use conditions (opens a new tab)
All formulas and masses below describe the neutral, anhydrous free acid. The solubility column preserves temperature and measurement basis; it is intentionally not a “most soluble” ranking.
| Acid / formula / g/mol | Structure / COOH | pKa and conditions | Water solubility | Application / distinction |
|---|---|---|---|---|
| Succinic acid C₄H₆O₄ 118.09 g/mol | HOOC–CH₂–CH₂–COOH Saturated C4 diacid; achiral 2 COOH | 4.207 / 5.636Water, 25 °C; thermodynamic, I = 0 | 83.2 g/L in water at 25 °C (PubChem/HSDB, Yalkowsky 2003). Supplier reference: 83 g/L at 25 °C. | Polyester monomer; conditional food pH-control useTwo methylene groups separate the carboxyl groups.Sources: PubChem (opens a new tab) · Goldberg, Kishore & Lennen (opens a new tab) · TCI America S0100 (opens a new tab) · Park, Jun & Im (opens a new tab) · 21 CFR 184.1091 (opens a new tab) |
| Malonic acid C₃H₄O₄ 104.06 g/mol | HOOC–CH₂–COOH Saturated C3 diacid; achiral 2 COOH | 2.852 / 5.697Water, 25 °C; thermodynamic values from extrapolated potentiometric measurements | No single comparison value: PubChem reports 623 g/L at 25 °C and 766 g/L at 20 °C, but also an ICSC entry of 7.3 g/100 mL at 20 °C. Unresolved disagreement. | Synthesis; malonic ester chemistry uses a derivativeOne methylene group between the two carbonyl carbons.Sources: PubChem (opens a new tab) · Kettler, Wesolowski & Palmer (opens a new tab) · OpenStax Organic Chemistry §22.7 (opens a new tab) |
| Adipic acid C₆H₁₀O₄ 146.14 g/mol | HOOC–(CH₂)₄–COOH Saturated C6 diacid; achiral 2 COOH | 4.44 / 5.44Water, 25 °C; IUPAC compilation via PubChem; ionic strength not stated in extracted record | 22 g/L in water at 20 °C (TCI reference). Temperature differs from the succinic acid value. | Nylon 66 monomer with a diamineFour methylene groups; a different polymer repeat unit.Sources: PubChem (opens a new tab) · TCI A0161 (opens a new tab) · OpenStax Organic Chemistry §31.4 (opens a new tab) |
| Fumaric acid C₄H₄O₄ 116.07 g/mol | (E)-HOOC–CH=CH–COOH Unsaturated C4 diacid; trans (E) 2 COOH | 3.03 / 4.5425 °C, Merck Index via PubChem; ionic strength not stated. CRC gives 3.03 / 4.44 at 18 °C. | 6.3 g/L in water at 25 °C (TCI reference); method and solution pH not stated. | Food acidulant under its own US conditionsA C=C bond restricts rotation and adds alkene chemistry.Sources: PubChem (opens a new tab) · TCI F0067 (opens a new tab) · 21 CFR 172.350 (opens a new tab) |
| Citric acid (anhydrous) C₆H₈O₇ 192.12 g/mol | HOOC–CH₂–C(OH)(COOH)–CH₂–COOH C6 hydroxy tricarboxylic acid; achiral 3 COOH | 3.128 / 4.761 / 6.396Water, 25 °C; thermodynamic, I = 0 | 59.2% w/w at 20 °C (Merck Index via PubChem). This is a mass fraction, not 592 g/L of solution; no density-based conversion is made. | Food ingredient subject to FCC specifications and GMPThree carboxyl groups plus one alcohol group. Monohydrate is a different solid form.Sources: PubChem (opens a new tab) · Goldberg, Kishore & Lennen (opens a new tab) · 21 CFR 184.1033 (opens a new tab) |
Sources: PubChem: succinic acid, CID 1110 (opens a new tab) · Goldberg, Kishore & Lennen (2002), thermodynamic ionization constants; citrate §7.22, succinate §7.57 (opens a new tab) · TCI America S0100: US product and method-specific specifications (opens a new tab) · Park, Jun & Im (1998), direct esterification of succinic acid and 1,4-butanediol (opens a new tab) · 21 CFR 184.1091: succinic acid, US food-use conditions (opens a new tab)
Sources: PubChem: malonic acid, CID 867; attributed solubility records (opens a new tab) · Kettler, Wesolowski & Palmer (1992), malonic acid dissociation (opens a new tab) · OpenStax Organic Chemistry §22.7: malonic ester synthesis (opens a new tab)
Sources: PubChem: adipic acid, CID 196; IUPAC and Dean pKa compilations (opens a new tab) · TCI A0161: adipic acid reference properties (opens a new tab) · OpenStax Organic Chemistry §31.4: step-growth polymers (opens a new tab)
Sources: PubChem: fumaric acid, CID 444972; Merck and CRC pKa references (opens a new tab) · TCI F0067: fumaric acid reference properties (opens a new tab) · 21 CFR 172.350: fumaric acid and salts, US food-use conditions (opens a new tab)
Sources: PubChem: citric acid, CID 311; solubility bases differ (opens a new tab) · Goldberg, Kishore & Lennen (2002), thermodynamic ionization constants; citrate §7.22, succinate §7.57 (opens a new tab) · 21 CFR 184.1033: citric acid, US food-use conditions (opens a new tab)
Malonic solubility records have an unresolved order-of-magnitude disagreement. Citric data mix mass fractions and volume-based concentrations. For adipic acid, the IUPAC pair is 4.44 / 5.44, whereas Dean’s compilation gives 4.418 / 5.412 at 25 °C; the retrieved entries do not resolve method or ionic-strength differences. Fumaric pKa₂ differs between references at 18 and 25 °C. These are reasons to preserve attribution and conditions, not to average the numbers.
The acid molecules also have different crystal structures and ionization equilibria. Even matching temperature is not enough to predict dissolution in a buffered, saline or multicomponent formulation.
Succinic acid is not hazard-free because it occurs in metabolism. Sigma’s 398055 listing classifies serious eye damage (H318). The reviewed Wako English Japan/JIS SDS identifies skin and serious eye irritation (H315/H319). These product and jurisdiction records differ; do not replace the more severe classification with the milder one.
The Wako SDS calls for avoiding dust generation and skin/eye contact, appropriate ventilation and protective equipment, and separation from strong oxidizers. It identifies carbon oxides among thermal decomposition products. Obtain the current SDS for your exact product and destination before handling; this overview is not a complete exposure assessment, first-aid procedure or storage instruction.
Sources: Sigma-Aldrich 398055: US product, specifications and safety listing (opens a new tab) · Wako 19-0433: English Japan/JIS SDS, revision 16 February 2023 (opens a new tab)
The neutral four-carbon diacid HOOC–CH₂–CH₂–COOH, also called butanedioic acid (CAS 110-15-6). It is a crystalline solid under ordinary room conditions.
It is a synthesis and polyester feedstock and has specified food flavor/pH-control uses. Succinate’s metabolic role and a finished polymer’s uses belong to different chemical forms; see the application evidence above.
Yes. About 83 g/L at 25 °C is a commonly cited reference. Temperature, ionization and other ingredients matter; that figure does not specify how quickly a powder dissolves.
Approximately 4.21 and 5.64 in water at 25 °C. The NIST thermodynamic selection is 4.207 and 5.636 at zero ionic strength.
Succinic acid has two acid protons. Hydrogensuccinate has lost one, and succinate has lost both. A succinate salt adds counterions and may include water of crystallization.
Succinic acid has two methylene groups between its carboxyl groups; malonic acid has one. That changes first dissociation, molecular weight and synthetic behavior.
Fumaric acid contains a trans C=C bond; succinic acid is saturated. The cited 25 °C water-solubility references are lower for fumaric acid, but they do not predict every formulation.
No. Citric acid is a six-carbon hydroxy tricarboxylic acid with three acid dissociation steps. Formula, mass, speciation and application requirements differ.
The Succinic Acid Suppliers & Buying Guide contains product records, package prices, documentation notes and a local RFQ worksheet. Older links to this profile’s purchasing sections lead there when JavaScript is enabled.
Reviewed 2026-10-12. Identity records were independently retrieved from PubChem. Evaluated constants, attributed handbook entries, original research and supplier properties are identified separately above.