Dimethyl sulfoxide is an important polar aprotic solvent that can dissolve both polar and nonpolar compounds and is miscible in a wide range of organic solvents as well as water. Because it penetrates the skin very readily, it is sometimes used as a vehicle for topical application of pharmaceuticals.

Draw the structure of dimethyl sulfoxide. Include any nonbonding electrons on sulfur, and minimize formal charges by allowing sulfur to expand its octet.

To draw a structure first we need to know its molecular formula, which is C2H6SO for dimethyl sulfoxide. The central atom is sulfur, which is bonded to an oxygen and with two methyl groups (CH3).

Sulfur has 6 electrons in its valence shell, as so oxygen. To complete the octet of oxygen, 2 electrons will be shared by sulfur with it. So, it remains 4 electrons at the central atom. Carbon has 4 electrons in its valence shell, so it needs more 4 to be stable, and is already sharing 3 electrons with the hydrogens, thus, sulfur will share one electron with each one of them.

So, it will remain 2 nonbonding electrons in the central atom. According to the VSPER theory, to minimize formal charges, the structure would be a trigonal pyramid, but, the double bonding with oxygen has a large volume, then the geometry will be trigonal, as shown below.