5-Ethynyl Isophthalic Acid: Properties, Uses & FAQs

5-ethynyl isophthalic acid is a bifunctional aromatic building block combining two free carboxylic acid groups with a terminal alkyne substituent, making it a versatile linker for metal-organic framework (MOF) construction and copper-catalyzed azide-alkyne cycloaddition (CuAAC) click-chemistry applications.

CAS Number

Verify with current SDS; flag for review

Molecular Formula

C10H6O4

Molecular Weight

190.15 g/mol

Functional Groups

Two carboxylic acids (–COOH) and one terminal alkyne (–C≡CH)

Key Applications

MOF linker, CuAAC click chemistry, supramolecular assembly

Recommended Storage

Cool, dry place; protect from moisture and light

What Is 5-Ethynyl Isophthalic Acid?

5-Ethynyl isophthalic acid is a substituted isophthalic acid derivative in which a terminal alkyne group is installed at the 5-position of the benzene ring. Isophthalic acid itself (benzene-1,3-dicarboxylic acid) is a well-established ditopic carboxylate linker widely used in coordination chemistry and polymer science. The introduction of an ethynyl group at the 5-position adds a second orthogonal reactive handle without disrupting the geometry of the two carboxylate donors, so the molecule can simultaneously participate in metal coordination and covalent click-chemistry transformations.

The compound has the molecular formula C₁₀H₆O₄ and a molecular weight of approximately 190.15 g/mol. It is typically a white to off-white crystalline solid at room temperature.

Key Applications in Research

Metal-Organic Framework (MOF) Synthesis: The 1,3-disposed carboxylate groups of the isophthalate core adopt a characteristic angular geometry that directs the formation of specific network topologies in MOFs. Researchers employ 5-ethynyl isophthalic acid as a functional linker to embed alkyne handles directly into MOF pores or struts, enabling post-synthetic modification (PSM) via CuAAC click chemistry without dismantling the framework.

Click Chemistry and Bioconjugation: The terminal alkyne reacts selectively with organic azides under copper(I) catalysis (CuAAC) or, when strain-promoted, under metal-free conditions (SPAAC). This reactivity makes the compound useful for attaching fluorescent labels, peptides, or other functional modules to azide-bearing substrates, surfaces, or biomolecules.

Supramolecular Chemistry: The bifunctional nature of the molecule allows it to serve as a node or linker in hydrogen-bonded organic frameworks (HOFs) and other self-assembled architectures, where the alkyne may also participate in C–H···π or alkyne···alkyne interactions.

Handling, Storage and Safety

Storage: Store 5-ethynyl isophthalic acid in a tightly sealed container in a cool, dry location away from direct light and incompatible oxidising agents. Typical bench-stable carboxylic acid solids of this class do not require refrigeration under normal conditions, but long-term stocks benefit from storage at 2–8 °C to minimise any risk of slow oxidative degradation of the alkyne moiety.

Handling: Use standard personal protective equipment (PPE) including lab coat, nitrile gloves, and safety glasses. Handle the powder in a well-ventilated area or fume hood to avoid inhalation of fine particles. Consult the current Safety Data Sheet (SDS) supplied with the product for precise hazard classification and first-aid measures before use.

Solubility: The compound shows limited solubility in water due to the hydrophobic alkyne and aromatic core, but dissolves readily in polar aprotic solvents such as DMF, DMSO, and NMP, and in aqueous base upon deprotonation of the carboxylic acids.

Purity, Specification and Quality

Aladdin Scientific supplies 5-ethynyl isophthalic acid (SKU: B300243) as a research-grade reagent. Typical characterisation includes assessment by ¹H NMR to confirm structure and detect impurities, HPLC for purity determination, and elemental analysis or mass spectrometry as appropriate. Researchers should verify the current certificate of analysis (CoA) for the specific lot number to confirm purity and other release specifications prior to use in sensitive applications such as MOF crystallography or quantitative bioconjugation assays.

If a higher purity grade or custom pack size is required for a specific application, contact Aladdin Scientific's technical support team to discuss available options.

Ordering and Availability

5-Ethynyl isophthalic acid is available from Aladdin Scientific under SKU B300243. To place an order, visit the Aladdin Scientific website, search by product name or SKU, and add the desired quantity to your cart. Bulk quantities, institutional purchase orders, and invoice billing are supported. For stock availability, lead times, or volume pricing enquiries, contact the Aladdin Scientific sales or customer-service team directly. Ensure compliance with your institution's chemical procurement and safety approval processes before ordering.

Frequently asked questions

What is 5-ethynyl isophthalic acid used for?

5-Ethynyl isophthalic acid is primarily used as a bifunctional linker in the synthesis of metal-organic frameworks (MOFs), where its two carboxylate groups coordinate to metal nodes and its terminal alkyne enables post-synthetic modification via CuAAC click chemistry. It is also employed in bioconjugation, supramolecular assembly, and as a building block for functionalised polymers.

What solvents are recommended for dissolving 5-ethynyl isophthalic acid?

Due to its aromatic and alkynyl character, 5-ethynyl isophthalic acid has limited aqueous solubility at neutral pH but dissolves well in polar aprotic solvents such as DMF, DMSO, and NMP. It also dissolves in dilute aqueous base upon deprotonation of the carboxylic acid groups.

How should 5-ethynyl isophthalic acid be stored to maintain stability?

Store the compound in a tightly sealed container in a cool, dry location protected from light. For long-term storage, 2–8 °C is recommended to minimise oxidative degradation of the terminal alkyne functionality. Always consult the current SDS and certificate of analysis for lot-specific guidance.

Is 5-ethynyl isophthalic acid compatible with copper-catalysed click chemistry (CuAAC)?

Yes. The terminal alkyne of 5-ethynyl isophthalic acid is an ideal substrate for CuAAC reactions with organic azides, affording 1,4-disubstituted 1,2,3-triazole products under mild conditions. This makes it highly suitable for post-synthetic modification of MOFs and for bioconjugation strategies requiring orthogonal ligation chemistry.

What purity grade is Aladdin Scientific's 5-ethynyl isophthalic acid (B300243)?

B300243 is supplied as a research-grade reagent. For the precise purity specification and analytical data applicable to your lot, please refer to the certificate of analysis (CoA) available from Aladdin Scientific. Contact technical support if a higher purity grade is required for your specific application.

References

1. Furukawa, H.; Cordova, K. E.; O'Keeffe, M.; Yaghi, O. M. The chemistry and applications of metal-organic frameworks. Science 2013, 341, 1230444. doi:10.1126/science.1230444
2. Kolb, H. C.; Finn, M. G.; Sharpless, K. B. Click chemistry: diverse chemical function from a few good reactions. Angew. Chem. Int. Ed. 2001, 40, 2004–2021. doi:10.1002/1521-3773(20010601)40:11<2004::AID-ANIE2004>3.0.CO;2-5
3. Cohen, S. M. Postsynthetic methods for the functionalization of metal-organic frameworks. Chem. Rev. 2012, 112, 970–1000. doi:10.1021/cr200179u

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