Chemical Identity and Structure

5-Carboxyvanillic acid belongs to the family of hydroxymethoxy-substituted benzoic acids, extending the well-known vanillic acid scaffold by the addition of a second carboxylic acid group at the 5-position of the aromatic ring. The parent compound, vanillic acid (4-hydroxy-3-methoxybenzoic acid), is a widely studied natural phenolic acid; the 5-carboxy derivative therefore carries a phenolic hydroxyl group, a methoxy group, and two carboxylate moieties on the same aromatic ring.

This combination of functional groups confers distinctive physicochemical properties: the compound is expected to be a solid at room temperature with moderate water solubility that increases markedly in alkaline conditions due to ionization of both carboxylic acid groups and the phenolic hydroxyl. The presence of multiple hydrogen-bond donors and acceptors makes it reactive toward esterification, amidation, and metal-chelation reactions, which underpin its utility as a synthetic building block.

Aladdin Scientific supplies 5-Carboxyvanillic acid under catalogue number C1056676. Researchers should consult the certificate of analysis (CoA) for lot-specific purity, melting point, and spectroscopic data prior to use.

Biological Occurrence and Metabolic Context

Phenolic acids structurally related to 5-Carboxyvanillic acid arise predominantly from the microbial and enzymatic degradation of lignin, one of the most abundant aromatic biopolymers in nature. Lignin is composed of guaiacyl, syringyl, and p-hydroxyphenyl units; its oxidative breakdown by white-rot fungi, bacteria, and plant peroxidases yields a spectrum of low-molecular-weight phenolic metabolites including vanillic acid, syringic acid, and their carboxylated variants.

5-Carboxyvanillic acid, with its additional carboxyl group relative to vanillic acid, is structurally consistent with further oxidation products along these catabolic routes. It is also structurally analogous to compounds in the protocatechuate and syringate degradation branches, which are well-characterized in Sphingomonas, Pseudomonas, and related soil bacteria. Researchers working on lignocellulose valorization, microbial metabolism, and plant secondary metabolite biosynthesis may employ this compound as a reference standard or metabolite probe.

It should be noted that the precise in vivo enzymatic steps leading specifically to 5-Carboxyvanillic acid require further literature verification, and users are encouraged to cross-reference primary metabolomics studies.

Research Applications

Biochemical Reference Standard and Metabolomics: High-purity 5-Carboxyvanillic acid serves as an authentic standard for LC-MS/MS and HPLC-based metabolomic analyses targeting lignin-derived phenolic acids in environmental, plant, or microbial samples. Accurate mass and retention-time matching against certified standards is essential for confident metabolite annotation.

Synthetic Chemistry: The compound's dual carboxylic acid groups and phenolic hydroxyl provide versatile handles for selective functionalization. It can serve as a monomer or building block in the synthesis of polyesters, polyamides, metal-organic frameworks (MOFs), and other functional materials. The phenolic OH can be selectively protected or coupled to impart specific properties to target molecules.

Antioxidant and Biological Activity Studies: Like other hydroxymethoxy benzoic acids, 5-Carboxyvanillic acid may exhibit radical-scavenging and antioxidant activity attributable to its phenolic hydroxyl group. Researchers investigating structure-activity relationships (SAR) within the phenolic acid family may use it as a test compound. Specific bioactivity data should be obtained from peer-reviewed primary literature.

Coordination Chemistry: The combination of phenolate, carboxylate, and methoxy groups creates a multidentate ligand scaffold suitable for coordination with transition and lanthanide metal ions, relevant to catalysis and materials science research.

Handling, Storage, and Safety Considerations

General Handling: As with all aromatic acid reagents, 5-Carboxyvanillic acid should be handled in a well-ventilated laboratory environment. Wear appropriate personal protective equipment (PPE) including nitrile gloves, lab coat, and safety glasses. Avoid generating fine dust during weighing; use a balance enclosure or work in a fume hood.

Storage: Store the compound in a tightly sealed container in a cool, dry location away from direct light and sources of oxidation. Desiccation is recommended to prevent moisture uptake, which can affect the accuracy of gravimetric measurements. Specific recommended storage temperature and shelf life should be confirmed on the product label and CoA supplied by Aladdin Scientific.

Solubility Tips: For aqueous assays, dissolution may be facilitated by first dissolving the compound in a small volume of dilute sodium hydroxide solution or DMSO, followed by dilution into aqueous buffer. Adjust pH carefully if biological activity assays require physiological pH, as both pKa values of the carboxylic acid groups and the phenolic pKa will govern speciation.

Safety Data: A full Safety Data Sheet (SDS) is available from Aladdin Scientific. Users should review the SDS before first use, paying particular attention to first-aid measures, disposal, and incompatibilities.