Is Cinnamic Acid Flammable?

In this article, we will answer the following question: “Is Cinnamic Acid Flammable?”, and also provide other important safety information regarding the compound.

Is Cinnamic Acid Flammable?

Cinnamic Acid is not considered much flammable, but it could catch fire. Its major risk is being an irritant substance. It could catch fire if enough heat is provided.

What Cinnamic Acid is?

Cinnamic Acid is an organic acid. It’s normally isolated from the oil of cinnamon bark.

It has antimicrobial effects against postharvest pathogens.

Its odor is honey-like and is used as a food additive.

What is it used for?

Cinnamic Acid can damage the plasma membrane of microorganisms, inhibiting the growth of pathogens.

It is used as a precursor in the formation of flavorings like methyl cinnamate (ethyl and benzyl as well).

Cinnamic Acid properties and chemistry

Cinnamic Acid is an organic compound. Like most of them, it’s highly soluble in organic solvents such as ethanol, hexene, and organic acids.

It presents a low solubility in water.

Cinnamic acid is synthesized by plants as an intermediate for other compounds. It serves antioxidant properties in their metabolism.

The acid can present some level of flammability because of its hydrocarbon chain.

It can also go by the following names:

  • (2E)-3-Phenylprop-2-enoic acid
  • trans-Cinnamic acid
  • Phenylacrylic acid
  • Cinnamylic acid
  • 3-Phenylacrylic acid
  • (E)-Cinnamic acid
  • Benzenepropenoic acid
  • Isocinnamic acid

But what is an acid?

In chemistry, acid is a substance capable of oxidizing other chemicals. 

Commonly, this oxidation happens because the acid has a hydrogen ion (proton) that can go loose easily. The easier this hydrogen leaves the molecule, the more acid it is.

Let’s take a look at the Cinnamic Acid structure.

Cinnamic Acid chemical structure.

Adapted from:

These two molecules are the exact same thing, we have simply drawn them in a way the carbon (C) and hydrogen(H) atoms are visible. Oxygen (O) atoms were already visible.

In organic chemistry, we usually draw molecules using lines, for simplicity.

The hydrogen highlighted in green on the right is what we call ionizable hydrogen (or proton). This happens because there’s a specific electrical polarity in that side of the molecule that allows the hydrogen to leave.

You can also think about the oxygen molecule that was bonded with that hydrogen. Oxygens are much more stable when they have negative polarity around them because they are highly electronegative atoms. This negative polarity is nothing more than a pair of hydrogens.

Hydrogen, on the other hand, can become stable when it has a positive charge on it. This simply means that there’s an absence of electrons on H, which has lost its only hydrogen.

But the hydrogen is not sad because of that. It really appreciates giving his electron away, and oxygen loves receiving it.

We usually call this positive hydrogen ion “H+”.

Therefore, an acid is (usually) a chemical specie that’s able to donate its H+ and somehow be fine with that.

Acids can oxidize other chemicals (normally bases) because H+ can steal electrons from them, which is essentially Oxidation.

Cinnamic Acid Flammability

Cinnamic acid can catch fire but the fire hazard is not high.

One of the most common standard systems for the identification of hazardous materials is the NFPA 704. 

It has the shape of a diamond, has four divisions, and each color states a specific hazard.

Each compartment has a number. It’s a scale from 0 to 4, where zero means no hazard and 4 means a severe hazard.

The color-coded explanation is the following:

  • Red: Flammability risk.
  • Blue: Health-associated risk.
  • Yellow: Instability and reactivity.
  • White: Special/specific risks.


As you can see above, there is a risk of flammability when dealing with cinnamic acid, and also some health risks. The hazards are not big but they are possible.

A material with the flammability of 1 in this scale is something that requires considerable preheating so it can be available for catching fire.

It also means that the material could unleash suspended vapors that may ignite if a source of ignition is provided. This hazard is not possible in a well-ventilated area.

Cinnamic Acid can irritate the skin, eyes, and respiratory system.

If you require more specific information about the compound you can check its page in the National Library of Medicine, a reliable source.

For more information about Cinnamic Acid as a chemical product, you can check the safety data sheets from its manufacturers. 

For example (various countries): parchem, Acros, Alfa Aesar, and Sigma-Aldrich.  


Cinnamic Acid can ignite, but not spontaneously. It requires preheating or the formation of vapors due to long exposure in a room with bad ventilation. Sources of ignition are also required since it doesn’t burn spontaneously.

Frequently Asked Questions (FAQS): Is Cinnamic Acid Flammable?

Is Cinnamic Acid soluble in water?

No. Like most organic acids, solubility in water is considered very low.

Is Cinnamic Acid soluble in ethanol?

Yes. Its solubility in ethanol is considered high because its hydrocarbon characteristics are not too present.

Is Cinnamic Acid polar or nonpolar?

Cinnamic Acid is considered a nonpolar substance. It presents some polarity because it’s a carboxylic acid, but its carbon chain is long enough for it to acquire nonpolar characteristics;

Is Cinnamic Acid saturated or unsaturated?

Cinnamic Acid contains four unsaturations.

Is Cinnamic Acid aromatic?

Yes. Cinnamic acid contains an aromatic ring.

Is Cinnamic Acid toxic?

No. It’s even used as a food additive, hence its safety for humans.


Kuchi, V. S., Ilahy, R., & Siddiqui, M. W. (2018). Commercial Disinfectants in Skirmishing Postharvest Diseases. Postharvest Disinfection of Fruits and Vegetables, 273–292. doi:10.1016/b978-0-12-812698-1.00015-7

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