Dimethyl Sulfoxide

What is dimethyl sulfoxide?

Dimethyl sulfoxide, also known as DMSO, is an organosulfur compound. DMSO is a polar aprotic solvent, meaning that it can dissolve ions along with polar protic solvents, but does not have an acidic hydrogen in its structure. DMSO is also miscible in organic compounds and water, meaning that it will form a homogeneous solution when mixed with an organic compound or water.

DMSO is actually a by-product from the process of converting wood into wood pulp. This process also creates dimethyl sulfide, which, when oxidated with oxygen or nitrogen dioxide, can create DMSO.

DMSO has a wide variety of uses, ranging from biological and medicinal to everyday household uses. DMSO, while studied greatly throughout the years, is still not understood very well, due to the controversy surrounding its various uses in medical treatments. For example, in 1965 an Irish woman died due to DMSO treatment for a sprained wrist, causing all DMSO studies to come to a halt. The FDA later approved DMSO for treatment of interstitial cystitis, a bladder disease. Only then did DMSO studies begin to expand.

Bond Nature

Let's take a look at the nature of each bond in DMSO.

O=S: 3.5 - 2.6 = 0.9

The double bond between oxygen and sulfur is a moderately covalent polar bond.

S-C: 2.6 - 2.5 = 0.1

The single bond between sulfur and carbon is an extremely covalent polar bond.

C-H: 2.5 - 2.2 = 0.3

The single bond between carbon and hydrogen as a very covalent polar bond.

--Note that all the bonds are covalent polar bonds.

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Have a lot of unwanted paint in your house? Working in a bio lab and need to use PCR? Have interstitial cystitis? Well look no further than dimethyl sulfoxide!

Dimethyl sulfoxide, more commonly known as DMSO, is an effective paint stripper. Get rid of that unwanted coat of paint that you've been dying to get rid of.

DMSO has also been shown to inhibit secondary structures in DNA primers when using PCR. Add it to the mix before the reaction, and you'll be reducing the chance of an unwanted, interferring reaction!

DMSO is currently used in treatment against interstitial cystitis, a urinary bladder disease. Aren't you tired of the pain? Ask your doctor about DMSO treatments.

DMSO - the colorless, nontoxic liquid that you need to have in your house.

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Intermolecular Forces

Between two DMSO molecules, there two three intermolecular forces present: London dispersion forces and dipole-dipole forces.

First, London dispersion forces are present in all molecules, polar and nonpolar alike. The force is a force of attraction between any two molecules that forms temporary dipoles which are caused by the movement of electrons around two atoms. One end of a polar molecule can become temporarily positive, while another end can become temporarily negative. These temporary dipoles allow for two DMSO molecules to be attracted to each other.

Second, dipole-dipole forces are present in all polar molecules, which really are dipoles. A dipole-dipole force is an electrostatic attraction caused by the positive end of one dipole being attracted to the negative end of the other dipole. Between two DMSO molecules, the oxygen of one DMSO molecule would be attracted to the hydrogen of the other DMSO molecule. In the diagram below, the dotted line represents the electrostatic force between the two DMSO molecules.

Now, hydrogen bonding is a special case of dipole-dipole attraction, in which a temporary covalent bond forms between the hydrogen of one molecule and the oxygen, nitrogen, or fluorine of an adjacent molecule. In the case of DMSO, hydrogen bonding cannot occur! DMSO is a polar aprotic solvent. An aprotic solvent is a solvent that cannot donate hydrogen. A polar aprotic solvent is an aprotic solvent that lacks an acidic hydrogen. Therefore, hydrogen bonding is not present in DMSO, it being a polar aprotic solvent.

Polarity

DMSO, (CH₃)₂SO, is a polar molecule. There is an uneven distribution of electrons in the molecule. Oxygen, bonded to sulfur, has two unshared electron pairs! These unshared pairs cause the oxygen to be extremely negative, the root cause of the uneven distribution of charge throughout the molecule.