Glyoxylic Acid (298-12-4) Physical and Chemical Properties
Glyoxylic Acid
A small alpha‑keto monocarboxylic acid used as a reactive intermediate and reagent in specialty chemical synthesis, analytical workflows and formulation R&D.
| CAS Number | 298-12-4 |
| Family | Alpha-keto carboxylic acids |
| Typical Form | 50% aqueous solution (viscous liquid) |
| Common Grades | EP, USP |
Glyoxylic acid is a simple alpha-keto monocarboxylic acid (2-oxoacetic acid) belonging to the class of organic acids and specifically the aldehydic/alpha-keto acids. Structurally it can be described as acetic acid bearing an oxo group at the alpha carbon; the constitution is compact (formula C2H2O3) and the molecule contains a carbonyl adjacent to a carboxylic acid group, giving a conjugated set of polar functional groups (aldehydic/keto and carboxyl). Electronic features include a localized carbonyl pi system capable of nucleophilic addition and acid–base behaviour dominated by the carboxyl proton; the alpha-carbonyl stabilizes the conjugate base (glyoxylate) by inductive and resonance effects relative to simple carboxylic acids.
The compound is highly polar and water‑soluble, with low lipophilicity (negative logP/XLogP values). As an alpha‑keto acid it is chemically reactive: it undergoes acid–base dissociation (pKa in the weak acid range), hydrations/hemiketals and can be further oxidized to oxalic acid under certain conditions; it also forms hydrates and polymeric/syrupy materials on exposure to moisture (deliquescence). In practice glyoxylic acid is typically handled and supplied as aqueous solutions (frequently near 50% w/w) and is used industrially as an intermediate in fragrances, flavorings, pharmaceuticals, dye and polymer chemistry and as a specialty cleaning or corrosion‑inhibiting agent.
Common commercial grades reported for this substance include: EP, USP.
Basic Physical Properties
Density
Reported experimental densities include: - 1.342 (USCG, 1999) — denser than water; will sink. - 1.42 @ 20 °C/4 °C.
These values indicate that concentrated aqueous solutions and neat material are denser than water and will tend to sink in aqueous media. Bulk density can vary with hydration state and concentration of aqueous formulations.
Melting Point
Available experimental melting point data are variable: - 98 - 98 \(\mathrm{^\circ C}\) - Crystals from water; melting point: 70–75 \(\mathrm{^\circ C}\) (glyoxylic acid hemihydrate). - Crystals; MP: approx 50 \(\mathrm{^\circ C}\) (glyoxylic acid monohydrate). - −93 \(\mathrm{^\circ C}\)
Multiple melting points reflect different solid forms (anhydrous, hemihydrate, monohydrate) and strong hygroscopicity/deliquescence. Hydration state and sample history will strongly influence the observed melting behavior; reported lower melting points are consistent with hydrated or partially decomposed forms.
Boiling Point
No experimentally established value for this property is available in the current data context.
Vapor Pressure
A vapor pressure value is reported as 1.06 \(\mathrm{mmHg}\). An estimated vapor pressure of approximately 1 \(\mathrm{mmHg}\) at ambient temperature is also referenced in environmental fate descriptions. Vapor pressure and volatility of the neutral species are moderate; however, in aqueous media the compound is largely ionized (pKa ≈ 3.3) and the anionic form will not partition to the vapor phase.
Flash Point
No experimentally established value for this property is available in the current data context.
Chemical Properties
Solubility and Phase Behavior
- Very soluble in water; slightly soluble in ethanol, ethyl ether, and benzene.
- Supplied commercially as a 50% aqueous solution; physical description of that solution: colorless to straw yellow, viscous liquid.
- Solid forms: monoclinic crystals from water; rhombic prisms obtained from water with 1/2 mol of water of crystallization.
Glyoxylic acid is highly polar (multiple carbonyl and carboxyl oxygens, TPSA 54.4) and therefore shows high aqueous solubility; organic solvent solubility is limited. The substance is hygroscopic and deliquescent and tends to form syrups on short exposure to air, which is consistent with strong water uptake and the ability to form hydrates and oligomeric/hydrated species.
Reactivity and Stability
- Glyoxylic acid is corrosive and will attack many metals (with exceptions for some stainless steel alloys); contact with active metals can evolve hydrogen.
- It behaves as a typical carboxylic acid with respect to neutralization (exothermic with bases) and forms salts with bases and metals; it reacts with cyanides to release hydrogen cyanide in acidic conditions and can react with strong oxidizing or reducing agents.
- Thermal decomposition emits acrid smoke and fumes.
- It can be oxidized in biological and chemical contexts to oxalic acid; under some conditions enzymatic or chemical oxidation of glyoxylic acid yields oxalate.
- The material forms a syrup on short exposure to air (hemihydrate behavior) and is described as deliquescing quickly.
Practical implications: avoid mixing with incompatible reagents (strong oxidizers, strong bases in uncontrolled quantities, cyanides) and prevent contact with reactive metals. Use corrosion‑resistant materials for storage and handling.
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: C2H2O3
- Molecular weight: 74.04
- Exact mass / Monoisotopic mass: 74.000393922
These values describe a low‑molecular‑weight, highly oxygenated small organic acid.
LogP and Polarity
- XLogP3‑AA: −0.3
- Experimental log Kow (reported): log Kow = −0.07
- Topological polar surface area (TPSA): 54.4
- Hydrogen bond donor count: 1
- Hydrogen bond acceptor count: 3
- Rotatable bond count: 1
The negative logP/logKow values and significant TPSA are consistent with strong aqueous solubility and low potential for bioaccumulation. The molecule has one hydrogen bond donor (the carboxyl OH) and multiple acceptor sites (carbonyl and hydroxyl oxygens), enabling strong solvation and hydrogen‑bonding interactions in aqueous and polar environments.
Structural Features
- SMILES: C(=O)C(=O)O
- InChI: InChI=1S/C2H2O3/c3-1-2(4)5/h1H,(H,4,5)
- InChIKey: HHLFWLYXYJOTON-UHFFFAOYSA-N
- IUPAC/Computed name: oxaldehydic acid
Glyoxylic acid is an alpha‑keto acid (2‑oxoacetic acid, an aldehydic acid) featuring an electrophilic carbonyl adjacent to a carboxyl group; this structural motif confers reactivity toward nucleophiles (hydrate/hemiacetal formation, Schiff base chemistry in biological contexts) and susceptibility to oxidation to dicarboxylic products (e.g., oxalic acid) under appropriate conditions.
Identifiers and Synonyms
Registry Numbers and Codes
- CAS number: 298-12-4
- EC number: 206-058-5
- UNII: JQ39C92HH6
- UN number (noting concentration context in transport references): 3265 (GLYOXYLIC ACID (50% OR LESS))
- ChEBI ID: CHEBI:16891
- ChEMBL ID: CHEMBL1162545
- DrugBank ID: DB04343
- DSSTox Substance ID: DTXSID5021594
- HMDB ID: HMDB0000119
- KEGG ID: C00048
- NSC Number: 27785
- SMILES: C(=O)C(=O)O
- InChI: InChI=1S/C2H2O3/c3-1-2(4)5/h1H,(H,4,5)
- InChIKey: HHLFWLYXYJOTON-UHFFFAOYSA-N
Synonyms and Structural Names
Common synonyms and alternative names reported include: - 2‑Oxoacetic acid - Glyoxalic acid - Oxoacetic acid - Oxoethanoic acid - Formylformic acid - Oxalaldehydic acid - oxaldehydic acid - alpha‑Ketoacetic acid - Acetic acid, oxo- - Glyoxylate
(Additional depositor and historic synonyms exist for various salt and solution forms; the names above reflect core structural synonyms for the parent acid.)
Industrial and Commercial Applications
Representative Uses and Industry Sectors
Glyoxylic acid is used as an intermediate and specialty chemical in multiple sectors: - Intermediate in the manufacture of flavorings and fragrances (e.g., in vanillin synthesis) and perfumes. - Raw material or intermediate for pharmaceuticals, dyes, plastics and agricultural chemicals. - Cleaning agent for certain industrial cleaning applications. - Ingredient in cosmetics (buffering and formulation roles). - Specialty feedstock for biodegradable copolymer production and corrosion inhibitors.
It is frequently produced, handled and sold as aqueous solutions (commonly near 50% w/w) for industrial use.
Role in Synthesis or Formulations
Glyoxylic acid serves as an electrophilic C2 building block in organic synthesis (aldehyde/carboxyl reactivity), used to prepare esters, heterocycles and flavor precursors. It is also a precursor to methyl and other esters used in pesticide intermediate chemistry and acts as a chemical intermediate in routes to vanillin and related aromatics. In formulations, its acidity and oxidative chemistry are exploited in controlled reactions and as a reactant for derivatization or condensation steps.
Safety and Handling Overview
Acute and Occupational Toxicity
- Hazard classification summaries include: Met. Corr. 1 (may be corrosive to metals), Skin Sens. 1B (may cause an allergic skin reaction), Eye Damage 1 (causes serious eye damage). Reported GHS hazard statements include H317 (may cause an allergic skin reaction), H318 (causes serious eye damage), and H290 (may be corrosive to metals).
- Clinical/toxicological notes: contact with the substance can cause severe skin and eye burns; inhalation of vapors may cause respiratory irritation and chemical pneumonitis in severe exposures. Glyoxylic acid and its metabolites have biological activity and metabolic conversion to oxalate has been linked to renal effects in animal studies; occupational exposure should be controlled to avoid inhalation and dermal contact.
- Acute toxicity context: experimental and non‑clinical studies indicate mitochondrial respiration inhibition at high concentrations and potential for nephrotoxicity via oxalate formation in metabolic pathways; handle with appropriate engineering controls.
First aid highlights (generalized): remove contaminated clothing; flush skin or eyes with copious water for at least 15 minutes; move affected persons to fresh air for inhalation exposures and seek immediate medical attention.
Storage and Handling Considerations
- Store in corrosion‑resistant containers and secondary containment; avoid storage with incompatible materials (strong oxidizers, active metals, cyanides, strong bases unless specifically controlled).
- The material is deliquescent and forms a syrup on short exposure to air; maintain sealed containers and controlled humidity. Corrosion to metals and container materials is possible; use compatible materials such as suitable stainless steels or other corrosion‑resistant alloys as specified by supplier guidance.
- Spill and release: isolate area, use appropriate PPE (full impervious protective clothing, eye/face protection, respirator for vapors), neutralize with suitable neutralizing agents for acids (e.g., lime) when safe to do so, and collect neutralized residues for appropriate disposal.
- Firefighting: combustible but not easily ignited; when heated or involved in a fire containers may rupture and corrosive vapors and acrid smoke can be generated. Firefighting agents include dry chemical, CO2 or water spray; avoid direct contact between strong streams of water and concentrated acid without proper procedure.
- Personal protective equipment: gloves resistant to acids, full impervious protective clothing, chemical safety goggles or face shield and, where vapor exposure may occur, an approved respirator.
For detailed hazard, transport and regulatory information, users should refer to the product‑specific Safety Data Sheet (SDS) and applicable local legislation.
