Uric Acid (69-93-2) Physical and Chemical Properties
Uric Acid
A purine-derived oxopurine that is supplied as a white crystalline solid for analytical, research and formulation use.
| CAS Number | 69-93-2 |
| Family | Purines (oxopurines) |
| Typical Form | White crystalline solid |
| Common Grades | EP |
Uric acid is a substituted purine (oxopurine) of the general formula \(\ce{C5H4N4O3}\). The core structure is a bicyclic purine ring bearing carbonyl/oxo functionalities at positions 2, 6 and 8 and multiple labile protons; several tautomeric forms are described for the parent trioxopurine scaffold. Structurally, the molecule is highly polar, non‑alkylated, and essentially rigid (rotatable bond count = 0), giving it limited conformational flexibility despite an extended hydrogen‑bonding capability.
Electronically, the three oxo groups and multiple ring nitrogens confer pronounced electron delocalization across the heterocycle and a relatively low lipophilicity (negative LogP/XLogP). The compound is a weak acid with \(\mathrm{p}K_a = 5.4\), so at physiological and neutral pH it exists predominantly as the deprotonated urate anion and readily forms salts (e.g., sodium, potassium, ammonium urates). High polarity and extensive hydrogen‑bond donor/acceptor sites (H‑bond donors = 4; H‑bond acceptors = 3; TPSA = 99.3) control aqueous solubility and solid‑state aggregation; the low aqueous solubility underlies its biological tendency to crystallize as urate salts in pathological conditions.
Uric acid is a biologically relevant metabolite (final purine catabolite in humans) and a redox‑active small molecule with antioxidant/reducing properties. Industrially and in formulation contexts it appears in niche uses such as pH buffering and skin‑conditioning in cosmetic applications, and is supplied commercially in defined grades. 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
Reported melting point: greater than \(300\ ^\circ\mathrm{C}\) (values recorded as "Greater than 300 °C" and "> 300 °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 description entries report uric acid as a white, odorless crystalline solid (also described as a beige powder) and as a solid overall. Solubility values reported in the available data context include the numeric strings "60" and "0.06 mg/mL"; the latter is recorded explicitly as "0.06 mg/mL" and should be interpreted as a low aqueous solubility consistent with strong intermolecular hydrogen bonding and efficient crystal packing. The low solubility and the acid dissociation behaviour (\(\mathrm{p}K_a = 5.4\)) explain the common formation of urate salts and crystalline deposits in aqueous biological environments; conversion to soluble urate salts (e.g., sodium or potassium urate) is a typical strategy to increase apparent solubility in formulations.
Phase behavior: the compound is normally isolated as a crystalline solid; solid‑state properties such as crystal structure and density have been characterized in the literature (crystalline forms and unit‑cell data exist), and the compound forms stable anionic urate species under basic conditions.
Reactivity and Stability
Uric acid is a redox‑active oxopurine: it can act as a reducing agent/antioxidant in biological media and is produced in vivo by oxidation of xanthine/hypoxanthine via xanthine oxidase. The triketone/tri‑oxo substitution pattern endows the molecule with multiple tautomeric forms; tautomerism can influence protonation states, hydrogen‑bonding patterns and reactivity toward electrophiles. Chemically, the parent neutral compound is stable as a dry solid under ambient conditions but is readily ionized, forms salts and hydrates, and can be further oxidized in enzymatic or chemical oxidative pathways (in many non‑primate mammals enzymatic urate oxidation proceeds further to allantoin). In preparations and handling, avoiding strong oxidizing conditions and controlling pH will limit undesired transformations.
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: \(\ce{C5H4N4O3}\).
Molecular weight (reported): 168.11 (recorded value). Exact/monoisotopic mass reported as 168.02834000. For stoichiometry and mass balance calculations use 168.11 \(\mathrm{g}\,\mathrm{mol}^{-1}\).
LogP and Polarity
Reported partition coefficients include XLogP3‑AA = −1.9 and experimental LogP = −2.17; both values indicate low lipophilicity and strong preference for polar/aqueous phases when solubilized. Topological polar surface area (TPSA) = 99.3 Å^2 and hydrogen‑bond donor/acceptor counts of 4 and 3, respectively, corroborate a highly polar profile that limits membrane permeation and promotes strong intermolecular hydrogen bonding.
Structural Features
Primary computed and structural descriptors: rotatable bond count = 0 (rigid bicyclic purine core), heavy atom count = 12, formal charge = 0 for the neutral form. The IUPAC/computed name appears as 7,9‑dihydro‑3H‑purine‑2,6,8‑trione (and multiple tautomeric descriptors are documented). Key structural attributes are the three carbonyl (oxo) substituents on the purine scaffold which generate multiple hydrogen‑bond donor/acceptor sites and enable strong intra‑ and intermolecular H‑bond networks in the solid state. The molecule is achiral (no stereocenters defined).
SMILES, InChI and InChIKey (structural identifiers):
SMILES: C12=C(NC(=O)N1)NC(=O)NC2=O
InChI: InChI=1S/C5H4N4O3/c10-3-1-2(7-4(11)6-1)8-5(12)9-3/h(H4,6,7,8,9,10,11,12)
InChIKey: LEHOTFFKMJEONL-UHFFFAOYSA-N
Additional computed descriptors recorded include XLogP = −1.9, exact mass = 168.02834000, monoisotopic mass = 168.02834000, and complexity = 332.
Identifiers and Synonyms
Registry Numbers and Codes
CAS: 69-93-2
European Community (EC) / EINECS number: 200-720-7
UNII: 268B43MJ25
ChEBI: CHEBI:17775
ChEMBL: CHEMBL792
DrugBank: DB08844
NSC Number: 3975
SMILES, InChI, InChIKey are provided above (see Structural Features).
Synonyms and Structural Names
Common synonyms and depositor‑supplied names recorded include: uric acid; urate; 7,9‑dihydro‑1H‑purine‑2,6,8(3H)‑trione; 2,6,8‑trioxypurine; 2,6,8‑trihydroxypurine; trioxopurine; 1H‑purine‑2,6,8‑triol, among many variant systematic and vendor‑supplied labels. These synonyms reflect the tautomeric and naming variants of the trioxopurine core and the salt forms (e.g., monosodium urate).
Industrial and Commercial Applications
Representative Uses and Industry Sectors
Uric acid is principally important as a biological metabolite and biomarker in clinical and biochemical contexts (final purine catabolite in humans). In non‑clinical industrial contexts it appears as a functional ingredient in cosmetics for buffering and skin‑conditioning purposes and is reported as permitted as an inert ingredient in certain non‑food pesticide formulations. It is also used as a reference material and standard in analytical and spectroscopic workflows (mass spectrometry, NMR, IR) and is employed in biochemical research related to antioxidant/redox biology and purine metabolism.
Role in Synthesis or Formulations
In formulation chemistry, uric acid is most relevant as the neutral acid or as converted urate salts (sodium, potassium, ammonium) to modify solubility and ionic strength. The compound’s low neutral solubility and high polarity mean that formulation strategies typically rely on salt formation, solubilization with co‑solvents or complexation, or pH control to achieve desired delivery properties. In analytical chemistry and metabolomics, uric acid is a target analyte and standard; in medicinal research it is investigated for biological activity related to antioxidant properties.
If a concise application summary is required beyond the above, no additional application detail is available in the current data context; in practice the substance is selected based on the general properties described above.
Safety and Handling Overview
Acute and Occupational Toxicity
Reported hazard information indicates that uric acid is generally not classified as a severe GHS hazard in the majority of supplier notifications; however, product‑specific safety sheets note that it may cause irritation and that reproductive effects were observed in some animal studies (rats). As a low‑solubility particulate, uncontrolled dust generation can cause respiratory or eye irritation, and dermal contact should be minimized. From a biochemical standpoint, renal elimination is the principal route in humans; elevated systemic concentrations are associated with clinical conditions such as gout and kidney stone formation.
Storage and Handling Considerations
Handle uric acid like a typical low‑hazard, low‑volatility organic solid: minimize dust generation, use local exhaust ventilation and appropriate respiratory/eye protection when handling powders, and employ standard gloves and protective clothing. Store in tightly closed containers in a cool, dry place away from strong oxidizing agents and incompatible reagents; control of pH and exclusion of moisture will reduce degradation or caking. For detailed hazard, transport and regulatory information, users should refer to the product‑specific Safety Data Sheet (SDS) and local legislation.
