Because the concentration of anhydrous ethanol is too high, a protective layer is formed on the surface of bacteria. Ethanol is a nonpolar molecule. After the protective layer is formed, alcohol can't contact bacteria, so it can't be completely sterilized. However, 75% ethanol is usually used. Water molecules are polar molecules, and water and ethanol can be mixed and dissolved in any proportion. Pure ethanol can enter protein molecules in cells smoothly, and ethanol can penetrate smoothly, with better disinfection effect.

Extended data:

Function and use of anhydrous ethanol

1, which is widely used in medicine, paint, sanitary products, cosmetics, oil and so on, accounting for about 50% of the total consumption of ethanol.

2. Ethanol is an important basic chemical raw material, which is used to produce acetaldehyde, ethylene diene, ethylamine, ethyl acetate, acetic acid and chloroethane. , and derived from medicine, dyes, coatings, spices, synthetic rubber, detergents, pesticides and other products of many intermediates, there are more than 300 kinds of products.

3. Ethanol can be used as energy, and some countries have started to use ethanol alone or mixed with gasoline (10% or more) as automobile fuel to save gasoline.

Baidu Encyclopedia-Hygienic Standard for Alcohol Disinfectants