Dimethyl Sulfoxide (DMSO)

Dimethyl Sulfoxide (DMSO)

Other Names: Dimethyl sulfoxide, DMSO, Methyl sulfoxide, Methylsulfinylmethane, Sulfinylbismethane
Chemical Formula: C₂H₆OS
Molar Mass: 78.13 g/mol
CAS Number: 67-68-5
SMILES: CS(=O)C
Appearance: Colorless, clear liquid
Odor: Nearly odorless when pure; impure material may exhibit a characteristic sulfur-like odor

Dimethyl sulfoxide (DMSO) is a highly polar, aprotic organosulfur compound containing two methyl groups bonded to a sulfoxide functional group. Its molecular structure produces a large dipole moment and strong ability to interact with ions and polar molecules. DMSO is completely miscible with water and is also compatible with a broad range of organic solvents, making it one of the most extensively used polar aprotic solvents in laboratory chemistry. Its unusual combination of polarity, relatively high boiling point and chemical versatility has resulted in extensive investigation of DMSO in solution chemistry, spectroscopy, electrochemistry, organic synthesis and materials science.

Chemical and physical properties

DMSO is a colorless liquid at room temperature, although its relatively high freezing point means that it can crystallize under cool laboratory conditions. Experimental data report a melting point of approximately 18.5 °C and a boiling point of approximately 189 °C at atmospheric pressure.

The density of DMSO is approximately 1.10 g/cm³ at 20 °C. It has a dynamic viscosity of approximately 2.0 mPa·s at 25 °C and a relatively high dielectric constant of about 47 at 25 °C, reflecting its strongly polar character.

DMSO is completely miscible with water. The sulfoxide oxygen is a strong hydrogen-bond acceptor and forms pronounced intermolecular interactions with water molecules and other hydrogen-bond donors. Spectroscopic and computational studies of DMSO–water mixtures demonstrate substantial changes in hydrogen-bond organization and molecular association as the composition of the mixture changes.

As a polar aprotic solvent, DMSO can efficiently solvate many cations while leaving certain anions comparatively reactive. This characteristic is important in numerous organic transformations and contributes to the ability of DMSO to dissolve a wide variety of inorganic salts, polar organic compounds and polymeric materials.

DMSO is hygroscopic and readily absorbs atmospheric moisture. Its physical properties, including viscosity, density, dielectric behavior and solvent characteristics, can therefore be influenced by water content. High-purity DMSO used in physicochemical and synthetic studies is commonly handled with attention to moisture contamination.

Applications

DMSO is widely used as a polar aprotic solvent in organic and inorganic chemistry. Its high polarity and broad dissolving capability make it suitable for reactions involving ionic reagents, nucleophiles and compounds that exhibit limited solubility in less polar organic solvents.

In synthetic organic chemistry, DMSO participates directly in several important oxidation reactions. Activated DMSO is employed in methods such as the Swern oxidation, in which primary and secondary alcohols can be converted into aldehydes and ketones, respectively. Related DMSO-based oxidation systems have been extensively investigated for selective transformations of alcohol functional groups.

DMSO is also widely employed as a reaction medium in nucleophilic substitution and other transformations in which a strongly polar aprotic environment can enhance the reactivity of anionic nucleophiles. Its high boiling point permits reactions to be performed over a relatively broad temperature range.

In polymer and materials science, DMSO is used as a solvent for the preparation, processing and characterization of numerous polymers and functional materials. It is also employed in solution-based synthesis of nanostructured materials, membranes, coatings and conducting polymers where high solvent polarity is required.

In electrochemical research, DMSO is used as a nonaqueous solvent and as a component of electrolyte systems. Its physicochemical properties have led to extensive investigation of ion solvation, electrode reactions and electrochemical processes in DMSO-based media.

DMSO is additionally used as a laboratory solvent for spectroscopic and analytical measurements. Deuterated dimethyl sulfoxide (DMSO-d₆) is particularly important in nuclear magnetic resonance spectroscopy because it dissolves a broad range of polar and moderately nonpolar compounds while providing a suitable deuterated medium for NMR analysis.

Scientific references

National Center for Biotechnology Information (NCBI), PubChem. Dimethyl Sulfoxide, CID 679. Chemical identity and physicochemical data including molecular formula, molecular mass, structure, melting point, boiling point and density.

Martin, D.; Weise, A.; Niclas, H.-J. The solvent dimethyl sulfoxide. Angewandte Chemie International Edition in English, 1967, 6(4), 318–334. DOI: 10.1002/anie.196703181.

Geissberger, P.; Séquin, U. Simple reaction monitoring of Swern oxidations. Tetrahedron, 2001, 57(18), 3861–3866. DOI: 10.1016/S0040-4020(01)00293-3.

Vishnyakov, A.; Lyubartsev, A. P.; Laaksonen, A. Molecular dynamics simulations of dimethyl sulfoxide and dimethyl sulfoxide-water mixture. The Journal of Physical Chemistry A, 2001, 105(10), 1702–1710. DOI: 10.1021/jp0007336.

Luzar, A.; Chandler, D. Structure and hydrogen bond dynamics of water-dimethyl sulfoxide mixtures by computer simulations. The Journal of Chemical Physics, 1993, 98, 8160–8173. DOI: 10.1063/1.464521.

Soper, A. K.; Luzar, A. A neutron diffraction study of dimethyl sulfoxide-water mixtures. The Journal of Chemical Physics, 1992, 97, 1320–1331. DOI: 10.1063/1.463259.

SAFETY

This product is not classified as dangerous.