Properties of alcohols: monohydric alcohols with one OH group

A medical student stole some liquid labelled ‘absolute alcohol’ to spike some drinks at the Christmas party. Some said ‘ Phew – that was some potent vodka!’ However, its high alcohol content immediately dehydrated the throat and stomach of some of the drinkers, causing much pain.Without treatment some could have died.

Pure ethanol, C2H5OH, is called ‘absolute ethanol’ and is used in medicine as a solvent, specimen storage liquid and cleansing agent. It mixes well with water and can be easily diluted. This property is unusual for covalent organic compounds as they are usually insoluble and immiscible in water. The solubility here is because of the similarity between the OH in the water structure, H OH, and the alcohol C2H5OH. Medicinal solutions in alcohol are called ‘tinctures’.

Ethanol, we know, is made when fruit sugars ferment. Ethanol (and methanol) can become an addictive material. Prolonged intake can damage tissues, particularly the liver. It has been found1 that people with alcohol dependency can be treated using a drug called ‘antabuse’ or disulfiran, which has no effect unless the person consumes alcohol. They then feel sick and nauseous, which is hoped will turn the person off alcohol. The drug acts by inhibiting the normal breakdown, within the body, of one of the oxidation products of alcohol, called ethanal. This builds up in the system, causing the nausea. The mechanism for its action follows the pathway: alcohol, C2H5OH ! by oxidation to ethanal, CH3CHO!further oxidation normally to CO2þH2O. In the case of antabuse, this last stage is prevented or delayed.