Cyclobutanone: Properties, Handling & Lab Use Guide

Cyclobutanone is a strained four-membered cyclic ketone widely used as a reactive building block in organic synthesis, medicinal chemistry, and mechanistic studies of ring-strain-driven reactivity.

Molecular Formula

C₄H₆O

Molecular Weight

70.09 g/mol

CAS Number

1191-95-3

Appearance

Colorless, volatile liquid with a pungent ketone odor

Key Reactivity Feature

Enhanced electrophilicity and ring-opening reactivity due to four-membered ring strain (~26 kcal/mol)

Primary Applications

Building block in total synthesis, β-lactam chemistry, cycloadditions, and drug discovery

Chemical Properties and Reactivity

Cyclobutanone (CAS 1191-95-3, MW 70.09 g/mol, molecular formula C₄H₆O) is the simplest isolable cyclic aliphatic ketone beyond cyclopropanone, featuring a four-membered carbocycle with a carbonyl group. The approximately 90° internal ring angles impose significant Baeyer strain, which elevates the electrophilicity of the carbonyl carbon relative to unstrained ketones such as cyclohexanone or acetone.

This ring strain confers several distinctive reactivity patterns:

• Enhanced nucleophilic addition: The strained carbonyl is more susceptible to attack by Grignard reagents, organolithiums, hydride reducing agents, and enamine-forming amines.
• Ring-opening reactions: Under appropriate conditions (strong nucleophiles, Lewis acid catalysis, or photochemical activation), the cyclobutane ring can undergo retro-[2+2]-type fragmentation or strain-release ring-opening, generating homoallyl or allyl intermediates.
• Enolate chemistry: Cyclobutanone forms enolates readily; these are useful in aldol-type condensations and alkylation reactions, where the adjacent ring strain influences regio- and stereoselectivity.
• Cycloadditions: The activated carbonyl participates in [2+2] and other cycloaddition reactions under photochemical or Lewis acid conditions, enabling rapid access to bicyclic and spiro frameworks.

The carbonyl stretching frequency of cyclobutanone appears at approximately 1780–1790 cm⁻¹ in the IR spectrum, notably higher than the ~1715 cm⁻¹ observed for acyclic or six-membered ring ketones, consistent with increased s-character of the carbonyl bond under ring strain.

Safe Handling and Storage

Cyclobutanone is a flammable, volatile liquid and should be handled with appropriate precautions consistent with standard laboratory ketone safety protocols. The following guidelines apply:

Personal Protective Equipment (PPE)

• Wear chemical-splash goggles, a lab coat, and solvent-resistant gloves (nitrile recommended) when handling cyclobutanone.
• Work in a well-ventilated fume hood at all times to prevent inhalation of vapors.

Fire and Explosion Hazards

• Keep cyclobutanone away from open flames, sparks, and hot surfaces. Use explosion-proof electrical equipment in areas where vapors may accumulate.
• Store away from strong oxidizing agents.

Storage Conditions

• Store in a tightly sealed container in a cool, dry, well-ventilated location, away from direct sunlight and heat sources.
• Recommended storage temperature: 2–8 °C (cold room or refrigerator dedicated to flammable solvents) or as specified on the product label.
• Ground and bond containers when transferring to prevent static discharge.

Spill and Disposal

• In case of spill, absorb with inert material (vermiculite, dry sand) and dispose of as hazardous chemical waste in accordance with local regulations.
• Do not pour down the drain.

Always consult the current Safety Data Sheet (SDS) supplied by Aladdin Scientific before use for the most current hazard and regulatory information.

Laboratory Applications and Synthetic Utility

Cyclobutanone serves as a versatile and strategically important intermediate in modern organic and medicinal chemistry. Its key laboratory applications include:

Building Block in Total Synthesis

The strained cyclobutane ring is found in a range of natural products and pharmaceutical targets. Cyclobutanone provides direct access to cyclobutane-containing scaffolds via reduction, reductive amination, Wittig olefination, or Baeyer–Villiger oxidation (yielding β-propiolactone derivatives), enabling efficient construction of carbocyclic and heterocyclic frameworks.

Baeyer–Villiger Oxidation

Treatment of cyclobutanone with peracids (e.g., mCPBA) effects Baeyer–Villiger oxidation to afford β-propiolactone (oxetan-2-one), a strained four-membered lactone itself useful as an electrophilic acylating agent and monomer. Regioselectivity in BV oxidation of cyclobutanone is well-established and predictable.

Enamine and Imine Formation

Cyclobutanone reacts readily with primary and secondary amines to form imines (Schiff bases) and enamines, respectively. These intermediates are valuable in asymmetric synthesis, organocatalysis, and the preparation of biologically active cyclobutylamine derivatives increasingly sought in drug discovery programs.

Photochemical [2+2] Cycloadditions

Under UV irradiation, cyclobutanone undergoes Norrish Type I and Type II photoreactions, producing reactive acyl and alkyl radical intermediates. Additionally, its carbonyl can engage in photochemical [2+2] cycloadditions with alkenes to build complex polycyclic architectures.

Drug Discovery and Medicinal Chemistry

Cyclobutyl motifs are increasingly valued as bioisosteres for gem-dimethyl groups and tert-butyl groups in drug design, improving metabolic stability and aqueous solubility. Cyclobutanone is the key precursor for introducing the cyclobutyl pharmacophore via reductive amination or Grignard addition to give cyclobutyl amines and alcohols used in medicinal chemistry campaigns.

Quality, Purity and Specification Considerations

For research applications, the purity and specification of cyclobutanone are critical parameters that directly influence experimental reproducibility. When selecting cyclobutanone for laboratory use, researchers and procurement teams should consider the following:

• Purity grade: For synthetic applications, reagent-grade cyclobutanone (typically ≥97–98% by GC) is suitable for most reactions. Highly sensitive reactions (e.g., asymmetric catalysis, kinetic studies) may require higher-purity material.
• Water content: As with all ketones, trace moisture can affect reactions involving enolate formation or Lewis acid catalysis. Where required, cyclobutanone should be dried over molecular sieves (3 Å or 4 Å) before use.
• Peroxide content: Like other ethereal or carbonyl compounds stored over time, cyclobutanone should be tested for peroxide formation before use in reactions involving strong bases or reducing agents. Peroxide test strips are recommended.
• Container integrity: Ensure the bottle seal is intact upon receipt. Any discoloration, turbidity, or unusual odor beyond the characteristic ketone smell should be flagged to the supplier.
• Certificate of Analysis (CoA): Request the CoA for each lot number from Aladdin Scientific to verify purity, identity (by NMR or GC-MS), and water content.

Aladdin Scientific (SKU: C107836) supplies cyclobutanone with documented quality specifications. Contact technical support for lot-specific CoA data or custom purity requirements.

Frequently asked questions

What makes cyclobutanone more reactive than other simple ketones?

Cyclobutanone's four-membered ring imposes significant Baeyer strain (~26 kcal/mol), which increases the electrophilicity of the carbonyl carbon and lowers the activation energy for nucleophilic addition relative to unstrained ketones. This is also reflected in its elevated carbonyl IR stretching frequency (~1780–1790 cm⁻¹ vs. ~1715 cm⁻¹ for six-membered ring ketones).

How should cyclobutanone be stored to ensure stability and purity?

Cyclobutanone should be stored in a tightly sealed container at 2–8 °C in a cool, dry, well-ventilated area away from heat sources, open flames, and strong oxidizers. Refrigerated storage in a flammable-solvent-approved refrigerator is recommended. Always check for peroxide formation before use if the reagent has been stored for an extended period.

What are the main synthetic uses of cyclobutanone in drug discovery?

In drug discovery, cyclobutanone is primarily used to introduce the cyclobutyl pharmacophore—a valuable bioisostere for gem-dimethyl and tert-butyl groups—via reductive amination with amines or Grignard addition with organometallics. The resulting cyclobutyl amines and alcohols are incorporated into drug candidates to improve metabolic stability, lipophilicity, and binding selectivity.

Can cyclobutanone be used in Baeyer–Villiger oxidation, and what is the product?

Yes, cyclobutanone undergoes Baeyer–Villiger oxidation readily with peracids such as meta-chloroperoxybenzoic acid (mCPBA) to yield β-propiolactone (oxetan-2-one), a strained four-membered lactone. This lactone is itself a useful electrophilic reagent in synthesis and a monomer in polymer chemistry.

What purity grade of cyclobutanone is appropriate for sensitive reactions such as asymmetric catalysis?

For highly sensitive reactions including asymmetric catalysis or kinetic studies, high-purity cyclobutanone (≥98% by GC) is recommended. Researchers should also ensure the material is dry (dried over 3 Å or 4 Å molecular sieves if necessary) and free from peroxides. Request the lot-specific Certificate of Analysis from Aladdin Scientific to verify purity before use.

References

1. March, J. Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 4th ed.; Wiley-Interscience: New York, 1992. (General reference for ketone reactivity and Baeyer–Villiger oxidation.)
2. Clayden, J.; Greeves, N.; Warren, S. Organic Chemistry, 2nd ed.; Oxford University Press: Oxford, 2012. (Ring strain, strained carbonyl IR frequencies, enolate chemistry.)
3. Turro, N. J.; Ramamurthy, V.; Scaiano, J. C. Modern Molecular Photochemistry of Organic Molecules; University Science Books: Sausalito, CA, 2010. (Norrish Type I and II photoreactions of cyclobutanone.)
4. Lovering, F.; Bikker, J.; Humblet, C. Escape from Flatland: Increasing Saturation as an Approach to Improving Clinical Success. J. Med. Chem. 2009, 52, 6752–6756. (Medicinal chemistry rationale for cyclobutyl bioisosteres.) doi:10.1021/jm901241e
5. Aladdin Scientific. Safety Data Sheet: Cyclobutanone, SKU C107836. (Consult current SDS for up-to-date hazard, storage, and regulatory information.)

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.