Isopropyl Alcohol Structure, Formula, & Uses

Formula and Chemical Structure

Isopropyl alcohol exists as an isopropyl hydrocarbon group that's linked to a single hydroxyl group. In chemistry, an alcohol is defined as any compound that contains one or more hydroxyl groups, thus the name. It has the chemical formula {eq}\text{C}_{3}\text{H}_{8}\text{O} {/eq}, although it's typically written out instead as {eq}\text{CH}_{3}\text{CHOHCH}_{3} {/eq} to emphasize that location of the hydroxyl group in the isopropyl chain.

Lewis structure of isopropyl alcohol, showing all individual bonds.

A line drawing of isopropyl alcohol. In this case, the solid lines represent the hydrocarbon chain

As mentioned earlier, isopropyl alcohol is a clear flammable liquid at standard temperature and pressure. However, the liquid form is very volatile, meaning it will quickly evaporate if left exposed. The vapors of isopropyl alcohol have a sharp odor, and large amounts can be irritating to the eyes, nose, and throat, so care should be taken to keep it away from the face during handling.

Production

Each year, millions of tons of isopropyl alcohol are produced around the world. The three main methods of producing it are:

• Indirect hydration of propylene
• Direct hydration of propylene
• Catalytic hydrogenation of acetone

All three methods start with a different compound called propylene, an organic gas that is typically obtained during the processing of natural gas.

Indirect Hydration of Propylene

The indirect process, also called the sulfuric acid process, involves mixing sulfuric acid and propylene together. This causes a reaction that produces what are known as sulfate esters, which are then broken down with water to form a variety of products, one of which is isopropyl alcohol.

Direct Hydration of Propylene

The direct process involves immediately mixing the propylene and water at high pressures, with either solid or liquid acidic catalysts included. The catalyzed reactions form isopropyl alcohol, which can then be distilled out of the water. The direct process has the advantage of being a single-step process, but it has the downside of requiring higher purities of propylene.

Catalytic Hydrogenation of Acetone

This process indirectly uses propylene, as it is often used prior to create acetone. In the catalytic process, acetone is mixed with hydrogen gas under high pressures to reduce the acetone to isopropyl alcohol. This reaction is catalyzed using metal crystals.

Uses for Isopropyl Alcohol

Isopropyl alcohol has a wide variety of uses, including but not limited to disinfecting agents, solvents, soaps, and lotions. Being relatively nontoxic, it has found its way into many homes and industries across the world.

Cleaning

Isopropyl alcohol mixes well with water, another solvent, to form a potent cleaning solution called rubbing alcohol. It cleans well because of its ability to dissolve oils on the surface of objects, and doesn't leave a streaked surface after evaporating. It is found in a variety of soaps and skin lotions, where its purpose is to clean the dirt and oils off our skin.

Bottles of isopropyl alcohol can be found at most convenience stores

Medical

Isopropyl alcohol can be used as an antiseptic and disinfectant, meaning it can kill disease-causing bacteria on the surface of our skin or other non-living objects. The exact mechanism responsible for it killing bacteria is not clear, but it could be due to the destruction of the cell's DNA and membranes. When used in this manner, isopropyl alcohol is typically mixed with water to form various concentrations of the chemical. Hand sanitizer is a great example of this, and typically contains 60-70% isopropyl alcohol.

Isopropyl alcohol is the main ingredient in most hand sanitizers

Automotive

Isopropyl alcohol is typically added to gasoline/petrol as a "gas dryer." Water and gasoline can't mix, so when water gets in a car's fuel tank it can accumulate and freeze in winter, possibly clogging the fuel lines. The isopropyl alcohol "solubilizes" the water suspended in the gasoline, meaning that it allows the two to mix. The water can then be consumed along with the fuel.

Isopropyl alcohol can also be used to dissolve and remove brake fluid, or it can be mixed with water to form a do-it-yourself wiper fluid.

Laboratory

Isopropyl alcohol can be used as a less toxic preservative, typically to replace formaldehyde. High concentrations are needed to preserve biological specimens. It can also be used to extract DNA from cells, since DNA strands are insoluble in isopropyl alcohol.

Cosmetics

Isopropyl alcohol is often used in a variety of cosmetics, especially nail products. It is used to reduce foaming/bubbles and to reduce the viscosity of these products.

Most nail polishes contain isopropyl alcohol

What Isopropyl Alcohol Cannot Clean

While very good at killing most bacteria cells, it's good to keep in mind that isopropyl alcohol doesn't kill everything. In particular, microscopic mold and fungal spores are both quite resilient to isopropyl alcohol, due to the fact that those types of spores typically have a protective "shell" covering their entire surface. There are even specific types of bacteria that show resistance to alcohol-based disinfectants. One in particular, E. faecium, has become a leading cause of hospital-acquired infections in recent years due to a prevalence of alcohol-based disinfectants in hospitals.

Safety and Toxicology

When using isopropyl alcohol, always keep it away from any open flames or heat sources. Prolonged exposure to the skin or any exposure to the eyes can cause irritation, so gloves and glasses are recommended if handling large quantities. Isopropyl alcohol poisoning can occur from ingestion, skin absorption, or inhalation. Symptoms of this poisoning include headaches, dizziness, nausea, vomiting, and low blood pressure. Ingestion of large quantities can lead to a coma, or even death.

Never use isopropyl alcohol close to an open flame

Isopropyl alcohol and rubbing alcohol are often denatured, meaning they have additives to make them poisonous, taste or smell bad, or create a feeling of nausea. These are added after production to discourage consumption.

Lesson Summary

Isopropyl alcohol is an organic compound that exists as a clear, flammable liquid at room temperature. It is a very volatile substance, meaning that it will quickly evaporate to form vapors if left exposed to the air. The chemical formula for isopropyl alcohol is {eq}\text{C}_{3}\text{H}_{8}\text{O} {/eq}, but it is often written as {eq}\text{CH}_{3}\text{CHOHCH}_{3} {/eq} instead. Millions of tons are produced every year, and the three main production methods used today are:

• Indirect hydration of propylene
• Direct hydration of propylene
• Catalytic hydrogenation of acetone

Due to its ability to dissolve oils and kill most bacterial cells, isopropyl alcohol makes an excellent cleaning and disinfecting agent. When combined with water, it is often referred to as rubbing alcohol. It is often found in hand sanitizers and cleaning solutions, and its use even extends to the automotive, cosmetic, and laboratory industries. Although mostly nontoxic, exposure to large amounts of isopropyl alcohol can cause irritation to the skin, eyes, nose, and airways. Ingestion is not recommended, as it can lead to severe poisoning symptoms.