2-Methoxybenzoic acid (579-75-9) Physical and Chemical Properties
2-Methoxybenzoic acid
A benzoic acid derivative (o-anisic acid) supplied as a crystalline intermediate and analytical reference for synthesis, flavor development and laboratory R&D.
| CAS Number | 579-75-9 |
| Family | Benzoic acids |
| Typical Form | Powder or crystalline solid |
| Common Grades | EP, JP, Reagent Grade |
2‑Methoxybenzoic acid is an ortho‑substituted methoxybenzoic acid (o‑anisic acid) — the O‑methyl ether derivative of salicylic acid. Structurally it comprises a monosubstituted benzene ring bearing a carboxylic acid at C‑1 and a methoxy group at the ortho position (C‑2). The molecule is formally neutral, with a single hydrogen‑bond donor (the carboxylic OH) and multiple acceptor sites (carbonyl O and methoxy O), yielding modest polarity and the capacity for intermolecular and intramolecular hydrogen bonding in the crystalline and liquid states.
Electronically, the methoxy substituent is an electron‑donating group (+M effect) that donates electron density into the aromatic ring, while the carboxyl group is strongly electron withdrawing by resonance and inductive effects. This juxtaposition modulates aromatic reactivity (the methoxy tends to activate the ring toward electrophilic substitution at ortho/para positions, countered locally by the deactivating carboxyl function) and influences acid‑base behavior: the carboxyl proton is acidic in the typical benzoic‑acid range and the compound will form water‑soluble carboxylate salts upon neutralization. The methyl ether (O‑Me) is substantially less labile than a free phenolic OH and is resistant to hydrolysis under mild conditions, but can be demethylated under strong acidic or strong nucleophilic/oxidative conditions.
The substance is used industrially and analytically as a flavouring agent and is reported as the methyl ether analogue of salicylic acid with occasional pharmacological interest (reported role as a non‑steroidal anti‑inflammatory agent in historical or investigational contexts). Common commercial grades reported for this substance include: EP, JP, Reagent Grade.
Basic Physical Properties
Solid description and appearance are consistent across suppliers: white crystalline solid or white odorless powder. The substance is a crystalline material with low volatility at ambient temperature.
Density
No experimentally established value for this property is available in the current data context.
Melting Point
Reported melting point: \(106\,^\circ\mathrm{C}\).
The melting point is typical for small aromatic carboxylic acids with some intermolecular hydrogen bonding in the solid state; crystalline packing is influenced by both carboxyl dimerization and dipolar interactions with the methoxy group.
Boiling Point
Reported boiling point: \(279.00\) to \(280.00\,^\circ\mathrm{C}\) at \(760.00\,\mathrm{mmHg}\).
The high boiling point reflects the low volatility of the crystalline acid and the presence of strong intermolecular interactions (hydrogen bonding and polar contacts). Sublimation or decomposition can compete with boiling at reduced pressures.
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
Reported solubility data: - \(5\,\mathrm{mg}\,\mathrm{mL}^{-1}\) at \(30\,^\circ\mathrm{C}\). - Soluble in boiling water and in common organic solvents. - Freely soluble in ethanol.
As a benzoic acid derivative, aqueous solubility is strongly pH dependent: the neutral acid has limited water solubility at ambient temperature but converts to water‑soluble carboxylate anion upon basification. Solubility in polar organic solvents (ethanol, acetone, ethyl acetate) is good; the moderate lipophilicity and small size also allow solubility in some less polar organic media. In formulations, salt formation (e.g., sodium or potassium salts) is an effective route to increase aqueous solubility.
Reactivity and Stability
2‑Methoxybenzoic acid is chemically stable under normal laboratory handling conditions but shows the expected reactivity profile of an aromatic carboxylic acid and an ortho‑methoxy substituted aromatic ring: - The carboxyl group readily forms esters, amides, and carboxylate salts under standard synthetic conditions (acid chlorides, coupling reagents, direct esterification under acidic catalysis). - The methoxy group is relatively inert under neutral conditions but can be cleaved by strong acids (hydrolysis/demethylation) or by specialized demethylation reagents (e.g., strong nucleophiles or oxidative demethylation protocols). - The aromatic ring can undergo electrophilic substitution reactions with regiochemical outcomes influenced by the competing directing effects of the methoxy and carboxyl groups; electrophilic substitution typically favors positions activated by the methoxy substituent subject to deactivation by the carboxyl. - The compound is generally stable to moderate temperatures but will undergo oxidative degradation under vigorous oxidative conditions and may decarboxylate under extreme thermal/oxidative stress.
Storage under dry, cool conditions and protection from strong oxidizers or prolonged elevated temperatures is appropriate to minimize degradation.
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: C8H8O3
- Molecular weight: \(152.15\,\mathrm{g}\,\mathrm{mol}^{-1}\)
- Exact/monoisotopic mass: 152.047344113
LogP and Polarity
- Computed XLogP3: 1.6
- Reported LogP (experimental/computed): 1.59
- Topological Polar Surface Area (TPSA): \(46.5\,\text{Å}^2\)
- Hydrogen bond donor count: 1
- Hydrogen bond acceptor count: 3
- Rotatable bond count: 2
- Formal charge: 0
These parameters indicate modest lipophilicity with sufficient polarity to support limited aqueous solubility for the neutral acid and substantially increased solubility upon ionization. TPSA and H‑bond counts are consistent with potential for passive permeation in small‑molecule contexts but also predict significant aqueous solvation of the deprotonated form.
Structural Features
- SMILES: COc1ccccc1C(=O)O
- InChI: InChI=1S/C8H8O3/c1-11-7-5-3-2-4-6(7)8(9)10/h2-5H,1H3,(H,9,10)
- InChIKey: ILUJQPXNXACGAN-UHFFFAOYSA-N
Key structural notes: the ortho relationship between methoxy and carboxyl groups permits intramolecular dipolar interactions and potential intramolecular hydrogen bonding with the carboxyl OH acting as hydrogen donor and the methoxy oxygen as acceptor. The molecule is essentially planar in the aromatic region; substitution pattern produces asymmetric electronic distribution across the ring, influencing both reactivity and intermolecular packing in the solid state.
Identifiers and Synonyms
Registry Numbers and Codes
- CAS: 579-75-9
- EC number: 209-447-8
- UNII: 49WA6Z7GZA
- FEMA Number: 3943
- ChEBI: CHEBI:421840
- ChEMBL: CHEMBL192311
- DSSTox Substance ID: DTXSID3060376
- NSC Number: 3778
- Additional registry entries and vendor identifiers exist and may be used for procurement and regulatory cross‑reference.
Synonyms and Structural Names
Common synonyms reported for this substance include: - 2‑Methoxybenzoic acid - o‑Anisic acid - o‑Methoxybenzoic acid - O‑Methylsalicylic acid - Salicylic acid methyl ether - 2‑Anisic acid - Benzoic acid, 2‑methoxy‑
These names are used interchangeably in chemical literature, regulatory listings, and product specifications; CAS number should be used for unambiguous procurement.
Industrial and Commercial Applications
Representative Uses and Industry Sectors
2‑Methoxybenzoic acid is used as a flavouring agent (FEMA listing and use in flavouring formulations) and has been evaluated for use in food‑related contexts. It is also encountered as a chemical intermediate in fine chemical and pharmaceutical synthesis where an ortho‑methoxybenzoic framework is required. The compound’s dual characteristics as a small aromatic acid and a methyl ether make it relevant to flavor & fragrance, pharmaceutical intermediate, and research chemical sectors.
Role in Synthesis or Formulations
In synthetic chemistry, 2‑methoxybenzoic acid serves as a building block for derivatization at the carboxyl function (esters, amides) and for further functional group manipulations on the aromatic ring. In formulations, it may appear as a flavor ingredient or odorant at low concentrations; its salt forms are used when increased aqueous solubility is required. Selection for a given application is typically based on its aromatic character, acidity, solubility behavior and odor/flavor profile.
Safety and Handling Overview
Acute and Occupational Toxicity
Hazard classification information indicates the substance is a skin and eye irritant in many notifications: - H315: Causes skin irritation. - H319: Causes serious eye irritation.
Reported acute toxicology notes include an intravenous LDLo reported as \(2{,}750\,\mathrm{mg}\,\mathrm{kg}^{-1}\) (rat, intravenous, contextually noted as a lowest‑observed lethal dose in specific study reports). At low levels of intake as a flavouring agent it has been evaluated without concern for human intake in those evaluations; nevertheless occupational exposure should be minimized.
Appropriate precautions: avoid skin and eye contact, minimize dust generation, employ local exhaust ventilation for particulate handling, and use suitable personal protective equipment (chemical‑resistant gloves, eye protection, protective clothing). In case of contact, follow standard first‑aid measures for chemical irritants (flush with water, seek medical attention for significant exposure).
Storage and Handling Considerations
Store in a cool, dry, well‑ventilated area in tightly closed containers away from strong oxidizing agents. As a solid powder/crystalline material, control of dust and good housekeeping reduce inhalation and cross‑contamination risks. The compound is not highly flammable in its solid form, but standard precautions for handling organic solids should be observed. For detailed hazard, transport and regulatory information, users should refer to the product‑specific Safety Data Sheet (SDS) and local legislation.
