Oxaloacetic Acid (328-42-7) Physical and Chemical Properties
Oxaloacetic Acid
A polar oxodicarboxylic acid used as a biochemical reagent and metabolic intermediate for enzymology, analytical standards, and formulation development.
| CAS Number | 328-42-7 |
| Family | Dicarboxylic acids |
| Typical Form | Powder or crystalline solid |
| Common Grades | EP |
Oxaloacetic acid is an alpha-keto dicarboxylic acid (a C4 oxodicarboxylic acid) that belongs to the oxo-dicarboxylic acid structural class. Structurally it is butanedioic acid bearing a carbonyl at the 2‑position; the molecule contains two carboxylic acid groups and an adjacent keto function which together produce a highly polar, hydrogen‑bonding capable scaffold. In solid form it is reported as an off‑white powder; in solution it readily ionizes to the mono‑ and dianionic oxaloacetate species, with the conjugate base commonly referred to as oxaloacetate.
Electronic and steric features impart pronounced polarity and aqueous solubility: the vicinal keto and carboxyl groups increase the topological polar surface area and facilitate strong intra‑ and intermolecular hydrogen bonding. Keto–enol tautomerism and facile deprotonation of the carboxyl groups govern speciation in solution and the compound behaves as a typical organic acid series member, with solubility and speciation highly dependent on \(\mathrm{pH}\). Lipophilicity is low (negative XLogP), consistent with the high hydrogen‑bond donor/acceptor counts and large polar surface area.
Biologically and industrially, oxaloacetic acid is a central metabolic intermediate (citric acid cycle) and a precursor in amino‑acid transamination (conversion to aspartic acid). It is used widely as a biochemical reagent and analytical standard and appears in investigational pharmaceutical contexts (noted investigational uses related to glutamate scavenging and neuroprotective interest). Common commercial grades reported for this substance include: EP.
Basic Physical Properties
Density
No experimentally established value for this property is available in the current data context.
Melting Point
161 °C
Boiling Point
No experimentally established value for this property is available in the current data context.
Vapor Pressure
No experimentally established value for this property is available in the current data context.
Flash Point
No experimentally established value for this property is available in the current data context.
Chemical Properties
Solubility and Phase Behavior
Physical descriptions list oxaloacetic acid as an off‑white powder and a solid. Reported solubility is 134 mg/mL (solvent not specified in the single solubility entry), consistent with a small, highly polar dicarboxylic acid that is readily soluble in polar protic solvents (water, aqueous buffers). In aqueous media the compound exists in acid–base equilibria (neutral acid, monoanionic and dianionic oxaloacetate forms) so that observed solubility and phase behavior are strongly \(\mathrm{pH}\) dependent. The molecule’s high topological polar surface area and multiple hydrogen‑bond donors/acceptors favor the hydrated, fully solvated state in aqueous solution.
Reactivity and Stability
Oxaloacetic acid is an alpha‑keto dicarboxylic acid capable of keto–enol tautomerism and the formation of enol/enolate species under basic conditions; anhydrous enol forms have been described separately. The presence of adjacent electron‑withdrawing carboxylate groups stabilizes the carbonyl but also makes the molecule susceptible to typical reactions of alpha‑keto acids: facile deprotonation at acidic sites, enolization, and participation in nucleophilic or condensation chemistry mediated by activated carbonyls. Enzymatic decarboxylation or transamination reactions are the dominant pathways in biological systems. Solid material is handled as a stable reagent under normal storage conditions, but solution chemistry (particularly at elevated temperature or extreme \(\mathrm{pH}\)) can alter speciation and occasionally lead to decomposition pathways characteristic for alpha‑keto dicarboxylates. No specific experimental decomposition temperatures or hydrolysis rate constants are available in the current data context.
Thermodynamic Data
Standard Enthalpies and Heat Capacity
No experimentally established value for this property is available in the current data context.
Molecular Parameters
Molecular Weight and Formula
Molecular formula: \(\ce{C4H4O5}\)
Molecular weight: 132.07
Exact mass / Monoisotopic mass: 132.00587322
Additional computed descriptors: heavy atom count 9; formal charge 0; covalently‑bonded unit count 1.
LogP and Polarity
XLogP3‑AA (reported): -0.6
Topological polar surface area (TPSA): 91.7
Hydrogen bond donor count: 2
Hydrogen bond acceptor count: 5
Rotatable bond count: 3
Complexity: 158
These descriptors are consistent with low lipophilicity, strong aqueous solvation, and extensive hydrogen bonding capacity; such properties explain the compound’s use in aqueous biochemistry and metabolomics workflows.
Structural Features
Oxaloacetic acid is an alpha‑keto dicarboxylate: two carboxyl groups are separated by two carbon atoms with a carbonyl at the alpha position. The carbonyl adjacent to a carboxyl creates resonance stabilization of enolate forms and increases acidity of the alpha proton(s) in the enolizable tautomer. Intramolecular and extensive intermolecular hydrogen bonding between carboxyl groups and the keto oxygen promote crystal formation in the solid state and strong solvation in polar solvents. Structural flexibility is moderate (three rotatable bonds) and the molecule lacks stereocenters in the canonical representation.
Identifiers and Synonyms
Registry Numbers and Codes
CAS number: 328-42-7
EC number: 206-329-8
UNII: 2F399MM81J
ChEBI: CHEBI:30744
ChEMBL: CHEMBL1794791
DrugBank: DB16921
KEGG ID: C00036
HMDB ID: HMDB0000223
NSC number: 77688
Key structural identifiers:
SMILES: C(C(=O)C(=O)O)C(=O)O
InChI: InChI=1S/C4H4O5/c5-2(4(8)9)1-3(6)7/h1H2,(H,6,7)(H,8,9)
InChIKey: KHPXUQMNIQBQEV-UHFFFAOYSA-N
Synonyms and Structural Names
Common synonyms and structural names reported for this substance include:
- Oxaloacetic acid
- Oxalacetic acid
- Oxaloacetate
- 2‑oxobutanedioic acid
- 2‑oxosuccinic acid
- Ketosuccinic acid
- Oxosuccinic acid
- Butanedioic acid, oxo-
- alpha‑Ketosuccinic acid
(Additional depositor and trade synonyms exist; the list above includes principal systematic and common names.)
Industrial and Commercial Applications
Representative Uses and Industry Sectors
Oxaloacetic acid is primarily used in biochemical, analytical and research contexts as a metabolic intermediate standard, enzymatic substrate, and analytical reference material for metabolomics and enzymology. It is a central metabolite of the citric acid cycle and an immediate precursor/intermediate in amino‑acid metabolism (transamination to aspartate). The compound has also been investigated in pharmaceutical research contexts, including investigational applications related to glutamate scavenging and putative neuroprotective effects; the compound has reached investigational clinical study stages (maximum reported clinical trial phase II across indications). Commercial material is available to support laboratory, analytical and preclinical uses.
Role in Synthesis or Formulations
In synthetic and biochemical processes oxaloacetic acid functions as a reactive intermediate: it participates in enzymatic transaminations (forming aspartic acid), condensations and decarboxylations. In preparative organic chemistry contexts it can be employed as a C4 building block where activated carbonyls or dicarbonyl chemistry is required. In formulation and analytical applications it is used as a reference standard for chromatography and mass spectrometry‑based metabolomics.
Safety and Handling Overview
Acute and Occupational Toxicity
Oxaloacetic acid is classified with corrosive/irritant hazard potential: it can cause severe skin burns and eye damage and is irritating to mucous membranes and the respiratory tract if inhaled as dust or aerosol. Reported acute effects include skin burns and corrosive injuries to the upper respiratory tract and lungs on significant exposure; some animal studies have reported convulsions following intraperitoneal dosing. Treat handling as for a corrosive organic acid: avoid direct contact and inhalation; implement engineering controls to limit dust and aerosol generation.
For workplace use, employ appropriate personal protective equipment (chemical‑resistant gloves, eye/face protection, lab coat) and local exhaust ventilation. For detailed hazard, transport and regulatory information, users should refer to the product‑specific Safety Data Sheet (SDS) and local legislation.
Storage and Handling Considerations
Store in a tightly closed container in a cool, dry, well‑ventilated area away from strong bases and oxidizing agents. Protect from moisture to limit conversion to enol/other forms where relevant for analytical consistency. Use procedures to control dust, provide spill containment materials, and have access to eyewash and safety shower facilities. Dispose of waste and aqueous solutions in accordance with local regulations and institutional procedures. For detailed hazard, transport and regulatory information, users should refer to the product‑specific Safety Data Sheet (SDS) and local legislation.
