Chloroform

Chloroform

Other Names: Trichloromethane, Methane trichloride, Trichloroform
Chemical Formula: CHCl₃
Molar Mass: 119.37 g/mol
CAS Number: 67-66-3
SMILES: C(Cl)(Cl)Cl
Appearance: Colorless, volatile liquid
Odor: Characteristic sweet odor

Chloroform, also known as trichloromethane, is a chlorinated methane derivative in which three hydrogen atoms of methane are replaced by chlorine atoms. It is a volatile molecular liquid with a tetrahedral carbon center and is one of the most extensively studied halogenated solvents. Its combination of relatively low polarity, high polarizability and ability to dissolve a wide range of organic substances has contributed to its extensive use in laboratory and industrial chemistry. Chloroform can also participate in intermolecular interactions as a weak C–H hydrogen-bond donor. Spectroscopic studies have demonstrated the formation of hydrogen-bonded complexes between chloroform and hydrogen-bond acceptors such as acetone and dimethyl sulfoxide.

Chemical and physical properties

Chloroform is a colorless and highly volatile liquid under ambient conditions. The NIST Chemistry WebBook reports a normal boiling temperature of approximately 334.3 K, corresponding to about 61.2 °C. Experimental melting-point measurements are close to 209.7 K, or approximately −63.4 °C.

Its density is approximately 1.48–1.49 g/cm³ near room temperature, making chloroform substantially denser than water. It has a relatively low dielectric constant of approximately 4.8 and is commonly classified as a weakly polar chlorinated solvent.

Chloroform has limited solubility in water but is readily compatible with many organic solvents. Its physicochemical properties make it particularly effective for dissolving numerous non-ionic and moderately polar organic compounds.

The hydrogen atom bonded to the carbon bearing three chlorine atoms displays enhanced acidity relative to hydrocarbons. As a result, chloroform can form weak C–H···X hydrogen-bonded complexes with suitable electron-donor molecules. These interactions have been investigated using NMR and ultrafast infrared spectroscopy and are useful model systems for studying weak intermolecular association and solvent dynamics.

Applications

Chloroform is widely used as an organic solvent in laboratory chemistry, particularly in extraction, purification, reaction processing and the preparation of solutions containing hydrophobic or moderately polar organic compounds. Chlorinated solvents including chloroform remain important reaction media because of their characteristic solvation properties, chemical stability under many reaction conditions and compatibility with numerous organic reagents.

In synthetic chemistry, chloroform can function not only as a solvent but also as a chemical reagent. Its C–H and C–Cl bonds can participate in transformations leading to chlorinated intermediates, carbon-containing products and reactive species generated under strongly basic, catalytic or radical conditions. The use of chloroform and related chlorinated solvents as reagents in organic synthesis has been extensively documented in the scientific literature.

Industrially, chloroform is an important chemical intermediate in the production of fluorinated compounds. A major application is its conversion to chlorodifluoromethane and related fluorocarbon intermediates used in the manufacture of fluorinated materials, including precursors associated with tetrafluoroethylene and polytetrafluoroethylene chemistry.

Chloroform is also extensively employed in physicochemical and spectroscopic research as a model chlorinated solvent. Studies involving chloroform have contributed to the understanding of hydrogen bonding, molecular association, solute–solvent exchange dynamics, thermodynamic properties and the behavior of chlorinated solvents in organic reaction systems.

Scientific references

• NIST Chemistry WebBook, SRD 69. Trichloromethane (CAS 67-66-3). National Institute of Standards and Technology. Thermodynamic and physicochemical data.
• PubChem. Chloroform, CID 6212. National Center for Biotechnology Information, molecular identifiers and chemical property database.
• Hansen C. M. et al. Chlorinated Solvents: Their Advantages, Disadvantages, and Alternatives in Organic and Medicinal Chemistry. Chemical Reviews, 2021, 121, 1582–1622. DOI: 10.1021/acs.chemrev.0c00709.
• Tlili A., Schranck J., Wu X.-F. The Application of Dichloromethane and Chloroform as Reagents in Organic Synthesis. In: Solvents as Reagents in Organic Synthesis, Wiley-VCH, 2017. DOI: 10.1002/9783527805624.ch4.
• Solute-Solvent Complex Switching Dynamics of Chloroform between Acetone and Dimethylsulfoxide – 2D IR Chemical Exchange Spectroscopy. Journal of Physical Chemistry B, 2008. Experimental study of chloroform hydrogen-bonding and solvent exchange dynamics.
• Association Constants and NMR Association Shifts for Several Chloroform-Base Hydrogen-Bonded Complexes. Journal of Molecular Spectroscopy, 1963, 10, 117–130. DOI: 10.1016/0022-2852(63)90159-0.

Safety

Signal Word: Danger

Handling and Storage
Storage Conditions: Store in tightly closed containers in a cool, dry, and well-ventilated area. Protect from light, heat, and incompatible materials such as strong bases and oxidizing agents.
Handling Precautions: Use in fume hoods. Avoid inhalation, ingestion, and skin contact. Handle with proper protective equipment and avoid prolonged exposure.