Cyclopropanecarboxylic Acid: Properties, Uses & FAQs

Cyclopropanecarboxylic acid is a strained-ring aliphatic carboxylic acid widely employed as a versatile building block in medicinal chemistry, agrochemical synthesis, and fine-chemical research.

Chemical Name

Cyclopropanecarboxylic acid

Molecular Formula

C4H6O2

Molecular Weight

86.09 g/mol

CAS Number

1759-53-1

Appearance

Colorless to pale yellow liquid

SKU

C106979

Primary Application

Organic synthesis building block, pharmaceutical intermediate

What Is Cyclopropanecarboxylic Acid?

Cyclopropanecarboxylic acid (CAS 1759-53-1, molecular formula C₄H₆O₂, MW 86.09 g/mol) is the simplest cyclopropane-containing carboxylic acid. It consists of a cyclopropane ring bearing a carboxylic acid (–COOH) functional group. The three-membered ring imparts characteristic ring strain, which influences the compound's reactivity and conformational properties relative to linear or larger-ring analogues.

At room temperature, cyclopropanecarboxylic acid is typically a colorless to pale yellow liquid with a faint characteristic odor. Its unique ring geometry makes it a valuable scaffold in drug design, as the cyclopropyl motif can improve metabolic stability, modulate lipophilicity, and enforce specific binding conformations in target molecules.

Physical and Chemical Properties

Cyclopropanecarboxylic acid shares the general reactivity of aliphatic carboxylic acids while exhibiting distinctive behavior arising from ring strain. Key chemical behaviors include:

• Acidity: The compound is a weak acid, as expected for a simple aliphatic carboxylic acid. The cyclopropyl ring has mild electron-donating character by hyperconjugation, slightly moderating acidity compared to acyclic analogues.
• Esterification and Amide Formation: Like other carboxylic acids, it reacts with alcohols (acid-catalyzed or via activated intermediates) to give esters, and with amines to give amides—reactions of central importance in pharmaceutical synthesis.
• Acyl Chloride Formation: Treatment with thionyl chloride or oxalyl chloride converts it to cyclopropanecarbonyl chloride, a reactive acylating agent widely used in synthesis.
• Ring Stability: The cyclopropane ring is retained under most standard synthetic conditions but can undergo ring-opening under strongly acidic, basic, or high-temperature conditions.

Note: Specific numerical values for boiling point, melting point, density, and pKa should be confirmed from the product certificate of analysis or authoritative chemical databases.

Applications in Research and Synthesis

Cyclopropanecarboxylic acid is a broadly useful building block across multiple research domains:

• Medicinal Chemistry: The cyclopropyl group is a well-established bioisostere and conformational constraint. Cyclopropanecarboxylic acid serves as a starting material or intermediate for incorporating this motif into drug candidates, potentially improving potency, selectivity, and pharmacokinetic profiles.
• Agrochemical Synthesis: The compound is used in the preparation of pyrethroid insecticides and related agrochemical intermediates, where the cyclopropane ring is a structural feature of numerous active ingredients.
• Polymer and Material Science: Cyclopropane-derived monomers and functional groups are explored in specialty polymer research.
• General Synthetic Chemistry: As an acylating precursor, it enables the preparation of cyclopropyl ketones, amides, esters, and other functionalized derivatives for structure–activity relationship (SAR) studies.

Handling, Storage, and Safety

As with all carboxylic acid reagents, appropriate precautions should be observed when handling cyclopropanecarboxylic acid:

• Personal Protective Equipment (PPE): Use chemical-resistant gloves, safety goggles, and a lab coat. Work in a well-ventilated area or fume hood to avoid inhalation of vapors.
• Storage: Store in a tightly sealed container in a cool, dry, well-ventilated location, away from incompatible materials such as strong oxidizers and bases. Check the product label and Safety Data Sheet (SDS) for specific storage temperature recommendations.
• Disposal: Dispose of waste material in accordance with local, regional, and national regulations for chemical waste.
• First Aid: In case of skin or eye contact, flush thoroughly with water. Consult the product SDS for full first-aid and emergency response information.

Always consult the current Aladdin Scientific Safety Data Sheet (SDS) for authoritative hazard and handling information before use.

Frequently asked questions

What is cyclopropanecarboxylic acid used for in research?

Cyclopropanecarboxylic acid is primarily used as a synthetic building block in medicinal chemistry, agrochemical research, and fine-chemical synthesis. It enables the introduction of the cyclopropyl motif—a bioisostere prized for improving metabolic stability and binding selectivity—into drug candidates and other target molecules. It is also a precursor to cyclopropanecarbonyl chloride and related activated acylating agents.

How should cyclopropanecarboxylic acid be stored to maintain quality?

Cyclopropanecarboxylic acid should be stored in a tightly sealed container under cool, dry, and well-ventilated conditions, away from incompatible substances such as strong oxidizers and strong bases. Always refer to the product label and the current Safety Data Sheet (SDS) provided by Aladdin Scientific for specific temperature and storage duration recommendations.

Is cyclopropanecarboxylic acid the same as cyclopropyl carboxylic acid?

Yes, cyclopropanecarboxylic acid and cyclopropyl carboxylic acid refer to the same compound (CAS 1759-53-1). Both names describe the carboxylic acid derivative of cyclopropane bearing a –COOH group directly attached to the ring. The IUPAC preferred name is cyclopropanecarboxylic acid.

Can cyclopropanecarboxylic acid be converted to an acyl chloride for synthesis?

Yes, cyclopropanecarboxylic acid is readily converted to cyclopropanecarbonyl chloride by treatment with thionyl chloride (SOCl2) or oxalyl chloride under standard conditions. The resulting acyl chloride is a highly reactive acylating agent used in Friedel–Crafts acylation, amide coupling, and other synthetic transformations.

What safety precautions are required when handling cyclopropanecarboxylic acid?

Researchers should wear appropriate PPE including chemical-resistant gloves, safety goggles, and a lab coat when handling cyclopropanecarboxylic acid. Operations should be conducted in a well-ventilated area or fume hood. Consult the Aladdin Scientific Safety Data Sheet (SDS) for complete hazard classification, exposure limits, and emergency response procedures before use.

References

1. March, J. Advanced Organic Chemistry: Reactions, Mechanisms, and Structure. Wiley-Interscience. General reference for carboxylic acid chemistry and cyclopropane ring properties.
2. Clayden, J.; Greeves, N.; Warren, S. Organic Chemistry, 2nd ed. Oxford University Press. Reference for acyl chloride formation and amide/ester synthesis.
3. Szeimies, G. Cyclopropane ring strain and reactivity in organic synthesis. General textbook-level reference.
4. Aladdin Scientific. Product page and Safety Data Sheet: Cyclopropanecarboxylic acid, SKU C106979. Aladdin Scientific.

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