Succinic Acid
Properties
| State | Solid (white crystalline powder with slight acidic taste) |
| Color | White |
| Solubility | Soluble in water (83 g/L at 25°C, 1210 g/L at 100°C); slightly soluble in ethanol; insoluble in ether |
| Melting Point | 185–187°C |
| Boiling Point | 235°C (decomposes to succinic anhydride and water) |
About Succinic Acid
Succinic acid is the four-carbon dicarboxylic acid HOOC–CH2–CH2–COOH (118.088 g/mol), named from Latin succinum (amber), because it was first distilled out of Baltic amber by Georgius Agricola in 1546. Inside every mitochondrion in your body, succinate is the substrate for succinate dehydrogenase (SDH, also called Complex II of the electron transport chain), which oxidizes it to fumarate and feeds the electrons into ubiquinone via covalently bound FAD. SDH is the only TCA-cycle enzyme also embedded in the inner mitochondrial membrane and the only one that does not produce NADH — it generates FADH2 instead, which is why each round of the cycle yields slightly less ATP from the succinate-to-fumarate step than from the NAD-linked oxidations. Pharmacologically, the SDH inhibitor malonate is the classic teaching example of competitive enzyme inhibition. Industrially, succinic acid was tagged in the 2004 US DOE Top 12 platform chemicals report as one of the highest-priority bio-based building blocks, and bacterial fermentation routes (Actinobacillus succinogenes, engineered E. coli, and Basfia succiniciproducens) now compete with the older n-butane oxidation/maleic anhydride hydrogenation route. The bio-route also fixes one molecule of CO2 per succinate produced, which gives it a negative process carbon footprint when run on cane sugar feedstock. Downstream, succinic acid feeds 1,4-butanediol (BDO), tetrahydrofuran (THF), gamma-butyrolactone (GBL), polybutylene succinate (PBS biodegradable plastic), and adipic acid alternatives.
Where you'll encounter it
If you've ever tasted unaged sake or a young dry white wine and noticed a faint salty, slightly bitter edge underneath the acidity, that's succinic acid — yeast produces 0.5–2 g/L of it during fermentation and it is a recognized component of umami when paired with the glutamate in shellfish broths and aged cheese. In the metabolism lab, anyone running Seahorse extracellular flux assays or Oroboros high-resolution respirometry uses succinate (typically 10 mM disodium succinate plus rotenone to block Complex I) as the standard substrate to isolate Complex II respiration. In the bioplastics industry, the BioAmber plant in Sarnia, Ontario produced bio-succinic acid commercially from 2015–2018 and the technology now lives on at Roquette and other producers feeding PBS resin manufacturers in Asia. And on the supplement shelf, amber succinate has been sold for decades as a hangover remedy in Russia and Eastern Europe — there is some clinical evidence it accelerates ethanol clearance via the TCA cycle.
Common Uses
- TCA cycle substrate for measuring Complex II respiration in mitochondrial assays
- Bio-based monomer for polybutylene succinate (PBS) biodegradable packaging films
- Feedstock for hydrogenation to 1,4-butanediol, THF, and gamma-butyrolactone
- Acidulant and umami enhancer in food (E363) — sake, soy sauce, processed seafood
- Buffer component in plating baths for nickel and zinc electrodeposition
- Anti-caking and pH-adjustment agent in pharmaceutical tablet formulations
- Starting material for synthesis of adipic acid via crossed Kolbe electrolysis
Safety Information
GRAS for direct food use under 21 CFR 184.1091 with no upper limit on quantity. ACGIH and OSHA have not set occupational exposure limits because the dust hazard is low. GHS classification: H319 causes serious eye irritation; no skin or inhalation classifications at the powder level. LD50 oral rat is 2,260 mg/kg, putting it in the same low-toxicity category as citric acid and malic acid. Concentrated solutions (above 5%) sting open cuts and irritate mucous membranes. The melt is corrosive at 185°C — handle with leather gloves, not nitrile, when transferring molten material in PBS pilot plants. Biodegradable and not classified as a marine pollutant.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.