Ethanol as a Solvent


Students learn to describe the uses of ethanol as a solvent and relate this to the polar nature of the ethanol molecule

If you look carefully at the molecular structure of ethanol, you can guess one of two things: either it will be soluble in a lot of things, or it won't be soluble in much of anything.

One end is a hydroxy group, -OH, or two-thirds of water molecule, which should go great in water.

The other end is a typical hydrocarbon, CH2CH3, which we might expect to be miscible with other hydrocarbons, such as hexane.

So one possibility is that these two factors will cancel each other out, making ethanol insoluble in everything. But we know that's not the case...

Ethanol is in fact very soluble in both hexane and water. If the hydrocarbon chain is lengthened to five carbon units (pentanol, or amyl alcohol) it will become insoluble in water, and if it shortened to one (methanol) it becomes much less soluble in hydrocarbons.

Ethanol has many industrial uses as a solvent, due to its relatively high affinity both for water and a great range of organic compounds.

Products largely based on ethanol include some solvent-based paints, lacquers, inks, household cleaning products, external pharmaceuticals (rubbing alcohol) and perfumes.

Since the hydrocarbon chain in ethanol is relatively short, the polar nature of the -OH group is still "visible" to other molecules. This makes the ethanol molecule polar overall, allowing its solubility in water.