Is Isopropyl Alcohol Flammable?

This article will answer the following question: “Is Isopropyl Alcohol Flammable?”. We will show the nature of this compound, how flammable it can be and in which conditions, other hazards, and relevant questions.

Is Isopropyl Alcohol Flammable?

Yes, isopropyl alcohol is flammable. It can easily be set on fire in usual conditions. The material has a low flashpoint, meaning it can become airborne easily. It liberates a lot of energy upon burning. 

What is isopropyl alcohol?

Isopropyl alcohol (IPA) is a chemical compound. It belongs to the chemical class of alcohol. It is a colorless and flammable compound that has a pungent alcoholic odor.

It is a volatile liquid that has a very low flashpoint, around 11ºC (53ºF). It’s mainly used as a disinfection agent. About one million tonnes of it is produced annually worldwide. 

It’s commonly used to clean electronic devices thanks to its high volatility. When applied to a surface the compound vanishes quickly, so there’s a low risk of damaging the components.

Can isopropyl alcohol catch fire easily?

Isopropyl alcohol is considered a highly flammable substance. There’s also a high risk of explosion if it gets in contact with oxidants, like hydrogen peroxide or chlorine compounds (Clorox).

It’s not like a huge and instant explosion, but if there’s only a little heat and light, hydrogen peroxide can start decomposing, creating reactive oxygen species that can attack IPA, eventually leading to a strong fire or explosion, bigger than burning IPA alone.

The most dangerous thing about isopropyl alcohol is not the total amount of energy liberated from its burning

Is isopropyl alcohol the same as rubbing alcohol?

More or less. Rubbing alcohol is a diluted version of isopropyl alcohol (IPA), which can contain other ingredients as well. 

Rubbing alcohol normally contains 70% isopropyl alcohol. Pure versions of IPA are considered too hazardous to be used at home, so they are mostly used by professionals or industries.

The risk of having pure isopropyl alcohol at home is just not worth it. A 70% solution of IPA presents enough disinfection power and would work practically the same.

Isopropyl alcohol chemistry

We will briefly discuss some important chemistry concepts to help help you have a better understanding of what isopropyl alcohol, is and why it presents different flammability.

The reader does not need to comprehend every in-depth content in this article, but we will do our best so everything is as simple as it gets.

What is alcohol?

In chemistry (more specifically, organic chemistry), alcohol is a molecule that has hydroxyl (-OH) ligands. The alcohol we drink (ethanol) gets this name because it’s the most common.

Organic molecules are carbon-based chain structures, where carbons are bonded to each other. 

The world “isopropyl alcohol” (or 2-propanol) already tells us what the molecule is like, in reality. We can separate the word into 3 parts:

iso propyl alcohol

“Equal” 3 carbons well.. alcohol (ligand)

By knowing this we can draw what an isopropyl alcohol molecule looks like. The “yl” is just a suffix.

The first structure is the most common way to write an organic molecule down. The carbons (C) and hydrogens (H) are hidden, but we know how many hydrogens it has because each carbon makes 4 connections.

The second structure is the same stick representation, but all atoms are visible. The last one is a 3D view.

What is an isomer?

Isomers are chemical molecules that have the same quantity and quality of atoms, but they are attached in a different way. For example:

Both structures have the formula C3H8O (or C3H7OH), but they are not the same thing. Some big molecules can have thousands of isomers.

Although similar, IPA does not has the same properties as 1-propanol. That hydroxyl radical in the middle of the molecule makes IPA boil sooner than its sister and becomes more reactive, and a little more flammable.

What is IPA used for?

It’s mainly used as part of the process of making other materials, such as:

  • Cleaners;
  • Cosmetics;
  • Perfume;
  • Antifreeze;
  • Medicaments;
  • Lacquers;
  • Dyes.

Rubbing alcohol, although, has more household uses. It’s used to disinfect wounds, and prevent infections, and some versions can relieve muscle aches. It’s also a disinfectant, for specific uses.

Is isopropyl alcohol hazardous?

It depends. If the person who’s handling it knows what the product is made of, how flammable it is, which are its specific properties, and the dangers related to using it, it can be considered safe.

The U.S FDA (Food and Drug Administration) agency classifies IPA as a “Safer Choice” when used as an antimicrobial agent or solvent.

The NFPA 704

Many government and non-governmental organizations establish systems, codes, and categories to express the overall hazards substances have.

The NFPA 704 is a standard maintained by the National Fire Protection Association, based in the U.S.

Also known as Safe Square and Fire Diamond, it uses a diamond with four divisions and colors. Each is rated on a scale of 0 to 4, known as Degrees of Hazard.

The four divisions have one color each. The red on top indicates flammability, the blue on the left indicates the level of health hazard, and the yellow on the right is for chemical reactivity. The white at the bottom contains codes for special hazards. 

Isopropyl alcohol safety and hazards

There’s only one major hazard associated with the compound: flammability. The specific hazards of rubbing alcohol are not exactly the same, but they are similar (although, much weaker ones).

The material can be easily ignited at usual temperatures. Due to its low flashpoint, flammable vapors can arise easily from it and travel until finding an ignition source.

Also, the flammability danger is even greater in the presence of an oxidizer.

Containers of the substance may explode upon heating.

It is considered a highly flammable and dangerous liquid and vapor. It may cause serious eye damage, drowsiness, and dizziness.

It can also be irritating for the skin and eyes. 

In the fire diamond diagram above you can see how the overall hazards of the compound are displayed. Other sources even categorize the flammability as “4”, the higher one.

Health hazards are not big but they are present.

How flammable isopropyl alcohol is?

We can only assess how flammable something is if we note how much energy it liberates, and compare it. Anything that’s considered flammable would liberate a good amount of energy in a short time.

Scientifically speaking, IPA liberates around 2000kJ of energy for each mole of the compound. We can write it as 1800kJ/mol, or 1.8MJmol-1

Mole is a quantity we use in chemistry, it’s associated with a certain number of particles. It’s the number of Avogrado, which is worth about 6.02×1023.

We are going to compare the same amount of other fuels, so it’s not important to understand what this number means.

  • Isopropyl Alcohol: 1829
  • 1- Propanol: 1843
  • Hydrogen: 286
  • Propane: 2044
  • Methanol: 639
  • Ethanol: 1230

We can say that IPA is much more flammable than common alcohol (ethanol), 8 to 9 times as flammable as hydrogen, 3 times more combustible than methanol, and almost as flammable as propane.

Propane is one of the main constituents of natural gas, the one we often use to cook our meals.

Therefore, we can say that isopropyl alcohol can unleash a great amount of energy upon burning. Combining this with the low flashpoint the substance presents, we can say that’s a fire hazard.

To better understand how hazardous the substance can be, let’s analyze some safety data sheets.

Isopropyl alcohol safety data sheets

Here you can check some safety data sheets for the product.

Conclusion

Isopropyl alcohol is a chemical compound that doesn’t present many hazards besides flammability, it’s even considered a “Safe Choice” according to the FDA. 

But the product is, indeed, flammable and can catch fire easily. It evaporates easily at room temperature, becoming airborne and capable of flying to an ignition source. Mists of IPA can lead to an explosion, so good ventilation is required.

Frequently Asked Questions (FAQS): Is Isopropyl Alcohol Flammable?

Isopropyl alcohol is a primary alcohol?

No, it’s a secondary alcohol. A primary alcohol is a molecule in which the hydroxyl ligand is attached to the first carbon of the carbon chain. In isopropyl alcohol, it’s in the second.

is isopropyl alcohol polar?

Most of the chemical bonds of isopropyl alcohol are non-polar. However, a small part of the molecule is indeed polar, a part that’s quite important. 

The carbon-oxygen bond of the molecule is polar because oxygen and carbon have a big electronegativity difference because oxygen has a bigger affinity with the electrons of the bond.

As a result, the electrons will get a little closer to the oxygen atom, creating a partial positive charge in the carbon, and the opposite in the oxygen, creating a polarity.

The overall polarity of the entire molecule is not big and is much lower than water polarity.

can i use rubbing alcohol instead of isopropyl alcohol?

Rubbing alcohol may contain other ingredients added to it such as wintergreen essential oil. Also, isopropyl alcohol is a pure version, while rubbing alcohol is around 70% concentrated. But the antimicrobial activity is similar.

Therefore, it depends on the use you will give to the products.

Citations

https://en.wikipedia.org/wiki/Isopropyl_alcohol_(data_page)
https://en.wikipedia.org/wiki/Isopropyl_alcohol
https://commonchemistry.cas.org/detail?cas_rn=67-63-0
https://pubchem.ncbi.nlm.nih.gov/compound/3776
https://www.epa.gov/saferchoice/safer-ingredients
https://www.epa.gov/saferchoice/safer-ingredients#pop67630
https://webbook.nist.gov/cgi/cbook.cgi?ID=C67630&Mask=2
https://www.fda.gov/

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