Alcohols & its Concentration

Alcohols : 

Alcohols are the family of compounds that contain one or more hydroxyl (-OH) groups attached to a single bonded alkane. Alcohols are represented by the general formula -OH.

Alcohols are important in organic chemistry because they can be converted to and from many other types of compounds.

70% Alcohol : 
Isopropyl alcohol, particularly in solutions between 60% and 90% alcohol with 10 – 40% purified water, is rapidly antimicrobial against bacteria, fungi, and viruses.

Once alcohol concentrations drop below 50%, usefulness for disinfection drops sharply. Notably, higher concentrations of alcohol don’t generate more desirable bactericidal, virucidal, or fungicidal properties.

90% Alcohol :
IPA do kill bacteria, but sometimes require longer contact times for disinfection, and enable spores to lie in a dormant state without being killed. 

In this analysis, a 50% isopropyl alcohol solution kills Staphylococcus aureus in less than 10 seconds , yet a 90% solution with a contact time of over two hours is ineffective. 

Some disinfectants will kill spores, which are classified as chemical sterilants. So why do higher alcohol solutions yield fewer results for bactericidal and antimicrobial outcomes?

A major industrial use of ethanol is to convert it by oxidation into acetaldehyde (CH₃CHO). Ethanol is also used in the preparation of various derivatives, such as ethyl chloride (used in the production of tetraethyllead), in the course of making various plastics, and in the usual further syntheses.

Isopropyl alcohol is mixed with water for use as a rubbing-alcohol antiseptic. ... In industry it is used as an inexpensive solvent for cosmetics, drugs, shellacs, and gums, as well as for denaturing ethanol (ethyl alcohol). 

Added to wet gas, it helps to prevent separation and freezing of a water layer.