CID 102089142 Physical and Chemical Properties
CID 102089142
The acetate anion is a common carboxylate used as a counter-ion, buffering component and reagent in synthesis and analytical workflows, often supplied as pharmaceutical-grade salts or isotopically labeled standards.
| CAS Number | Not specified for this entry |
| Family | Carboxylate anions |
| Typical Form | Aqueous solution / ionic salt |
| Common Grades | EP |
The substance is the acetate anion, an organic carboxylate derived from acetic acid; the recorded molecular formula corresponds to a deprotonated, doubly 13C‑labelled acetate (\(\mathrm{C_2H_3O_2^-}\)). Structurally it is a small, planar carboxylate with resonance‑delocalized negative charge across two oxygen atoms bound to a two‑carbon backbone. The provided structural identifiers indicate isotopic substitution at both carbon positions, which affects mass and spectrometric behavior but does not alter the basic electronic resonance of the carboxylate functional group.
Electronically, the anion is a weakly basic nucleophile with two hydrogen‑bond acceptor oxygens and no hydrogen‑bond donors; the negative charge is stabilized by resonance and solvation in polar media. The anion is polar and hydrophilic, with a modest calculated lipophilicity parameter and a moderate topological polar surface area. In aqueous systems, acetate is the conjugate base of acetic acid and participates in typical carboxylate chemistry (salt formation, coordination to metal cations, esterification/acetyl transfer when activated). Isotopic labelling makes this species useful for tracer and mass‑balance studies while preserving standard chemical behavior of acetate.
Common commercial grades reported for this substance include: EP.
Molecular Parameters
Molecular Weight and Formula
- Molecular formula: \(\mathrm{C_2H_3O_2^-}\) (deprotonated acetate with isotopic labelling indicated in structure).
- Molecular weight: \(61.029\,\mathrm{g}\,\mathrm{mol}^{-1}\).
- Exact/monoisotopic mass: \(61.020014005\,\mathrm{Da}\).
Qualitatively, the low molecular weight and small size confer high aqueous solubility for many counterion forms (e.g., alkali metal acetates). The presence of isotopic \(^{13}\)C labels increases the monoisotopic mass relative to the unlabeled anion and is relevant for mass spectrometric discrimination and tracer applications.
Charge State and Ion Type
- Formal charge: \(-1\).
The species is an organic anion (carboxylate). In typical environments it exists as a free anion paired with countercations (e.g., Na+, K+) or as part of ionic salts and complexes. The negative charge is delocalized over the two oxygens of the carboxylate group, reducing localized basicity relative to a non‑stabilized anion.
LogP and Polarity
- XLogP3 (computed): 0.4
- Topological polar surface area (TPSA): 40.1
- Hydrogen bond donors: 0
- Hydrogen bond acceptors: 2
The computed XLogP3 value \(0.4\) indicates weak lipophilicity; acetate is predominantly hydrophilic in neutral aqueous solutions. TPSA of \(40.1\) and the presence of two acceptor atoms are consistent with strong solvation and hydrogen‑bonding interactions with water, favoring aqueous phase partitioning and limited membrane permeability in its ionic form.
Structural Identifiers (SMILES, InChI)
- SMILES: [13CH3]13C[O-]
- InChI: InChI=1S/C2H4O2/c1-2(3)4/h1H3,(H,3,4)/p-1/i1+1,2+1
- InChIKey: QTBSBXVTEAMEQO-ZDOIIHCHSA-M
These identifiers reflect a doubly \(^{13}\)C‑labelled acetate anion; SMILES retains isotope labels explicitly. Such identifiers are useful for unambiguous computational, spectrometric and inventory purposes.
Acid–Base Behavior
Conjugate Acid and Speciation
The conjugate acid of the acetate anion is acetic acid (protonated carboxylic acid). In aqueous media, speciation between acetic acid and acetate depends on pH: under acidic conditions protonation to the neutral acid becomes favored, while under basic conditions the deprotonated acetate form predominates. As a carboxylate, acetate readily forms salts with common inorganic and organic cations and coordinates to metal centers in complexes.
Isotopic substitution at carbon does not materially change the acid–base equilibrium constants in a way that modifies typical chemical handling; small isotope effects on equilibrium are possible but generally minor for carbon isotopes.
Acid–Base Equilibria and Qualitative pKa Discussion
No experimentally established value for this property is available in the current data context.
Qualitatively, the carboxylate functional group is the conjugate base of a weak carboxylic acid and therefore exhibits typical weak‑base behavior in aqueous solution. Buffering capacity in acetate/acetic acid mixtures is widely used where near‑neutral pH stabilization is required; the position of the equilibrium is determined by the intrinsic acidity of the parent acetic acid and solution pH.
Chemical Reactivity
Chemical Stability
Acetate anion is chemically robust under ambient conditions and does not readily undergo oxidative degradation without specific strong oxidants or activated reaction partners. It is stable in aqueous solution and as salts under normal laboratory storage conditions. The resonance stabilization of the carboxylate reduces nucleophilicity relative to free alkoxide anions but still permits participation in nucleophilic substitution and coordination chemistry when activated or paired with appropriate electrophiles or metal centers.
Isotopic labelling does not significantly alter chemical stability for routine storage and handling, but it does change isotopic composition relevant to mass spectrometry and tracer studies.
Formation and Hydrolysis Pathways
- Formation: generated quantitatively by deprotonation of acetic acid or by neutralization of acetic acid with base, yielding the anionic form paired with a countercation.
- Reactivity pathways: participates in esterification and acyl transfer under activated conditions (for example, after conversion to an acyl chloride or anhydride), acts as a ligand in coordination chemistry, and serves as a nucleophile in some substitution reactions when appropriately activated.
Hydrolysis per se is not a primary reaction for the acetate anion; instead, transacylation or ester hydrolysis reactions involve acylated derivatives rather than the free carboxylate anion. When present as part of an ester or acetylated intermediate, hydrolytic cleavage can regenerate acetate under acidic or basic catalysis.
Identifiers and Synonyms
Registry Numbers and Codes
- Nikkaji Number: J2.477.700F
- InChIKey: QTBSBXVTEAMEQO-ZDOIIHCHSA-M
- InChI: InChI=1S/C2H4O2/c1-2(3)4/h1H3,(H,3,4)/p-1/i1+1,2+1
- SMILES: [13CH3]13C[O-]
- Molecular formula (computed descriptor): C2H3O2-
No CAS number is provided for this specific isotopically labelled anion in the current context.
Synonyms and Structural Names
- IUPAC/Common name (computed): acetate
- Related parent compound: Acetic acid-13C2 (parent compound identified for the labelled form)
These names reflect the generic carboxylate identity and isotopic labelling where applicable.
Industrial and Commercial Applications
Role as Active Ingredient or Intermediate
As a carboxylate anion, acetate commonly serves as a counterion in salts, a buffer component in biochemical and industrial formulations, and an intermediate or leaving group in acetylation and esterification chemistry. Isotopically labelled acetate variants are used as internal standards, tracers in metabolic studies, and for mass spectrometric calibration where a labelled acetate anion provides a distinguishable mass signature while retaining standard chemical reactivity.
Representative Application Contexts
Representative contexts include use as: - Component of buffer systems for biochemical and analytical workflows. - Counterion in salts used in synthesis and catalysis. - Reagent or intermediate in organic synthesis for forming esters and acetyl derivatives after appropriate activation. - Tracer or internal standard in isotope‑labelled studies and analytical chemistry when isotopic labels are present.
If a concise application summary is required for procurement or process design, selection should be based on the general physicochemical properties and isotopic labelling described above. No concise application summary is available in the current data context; in practice this substance is selected based on its general properties described above.
Safety and Handling Overview
Toxicity and Biological Effects
Acetate is a common endogenous anion in biological systems and, in typical concentrations from handling of acetate salts or dilute solutions, is not associated with severe acute toxicity; however, concentrated solutions or specific salt forms may pose irritation to skin, eyes and respiratory tract. As with all chemical materials, potential biological effects depend on concentration, counterion, route of exposure and isotopic labelling is not expected to introduce materially different toxicity profiles but may be relevant in tracer studies.
For health hazard assessment and exposure limits, refer to the specific product Safety Data Sheet and applicable occupational exposure guidelines.
Storage and Handling Considerations
Store in a cool, dry, well‑ventilated area in tightly closed containers to avoid contamination and moisture uptake where relevant. Avoid contact with strong oxidizing agents and incompatible materials; handle with appropriate personal protective equipment (gloves, eye protection and lab coat) and engineering controls (fume hood) to minimize inhalation and contact. For transport, detailed hazard classification is product‑specific and users should consult the product Safety Data Sheet and local regulations.
For detailed hazard, transport and regulatory information, users should refer to the product‑specific Safety Data Sheet (SDS) and local legislation.
