Difference Between PFOA and PFOS

The key difference between PFOA and PFOS is that PFOA has a carboxylic functional group, whereas PFOS has a sulfonic functional group.

PFOA and PFOS are organofluorine compounds. In other words, both these substances contain carbon atoms bonded with fluorine atoms. Therefore, these substances have a unique set of properties.

1. Overview and Key Difference
2. What is PFOA
3. What is PFOS
4. PFOA vs PFOS in Tabular Form
5. Summary

What is PFOA?

Perfluorooctanoic acid or PFOA is a type of perfluorinated carboxylic acid having the chemical formula C8HF15O2. The conjugate base of this compound is perfluorooctanoate. This substance has worldwide uses in chemical processes as a surfactant and as a material feedstock as well. However, due to various health concerns, there are some regulations for using this substance. This substance is considered a carcinogen.

When considering the chemical structure of PFOA, it has a perfluorinated n-octyl “tail group” and a carboxylated “head group.” This head groups are usually hydrophilic, and the tail group is both hydrophobic and lipophobic. Moreover, the tail group is inert and shows negligible chemical reactivity. Therefore, this tail group cannot undergo strong interactions with polar or nonpolar chemical moieties. In contrast, the head group is chemically reactive and can interact strongly with polar groups such as water. The lipophobic nature of the tail group comes from its fluorocarbon structure that is less susceptible to London forces than hydrocarbons.

PFOA has the chemical formula C8HF15O2, and the molar mass is 414.07 g/mol. It appears as a white solid that is partially soluble in water and soluble in polar organic solvents.

Figure 01: The Chemical Structure of PFOA

The major fields of applications of PFOA include carpeting, upholstery, apparel industry, floor wax production, textile industry, fire fighting foam, and sealant production. This substance can serve as a surfactant in emulsion polymerization or fluoropolymers. Also, it is useful as a building block for the production of perfluoroalkyl-substituted compounds, polymers, etc.

What is PFOS?

PFOS stands for perfluorooctanesulfonic acid. Its conjugate base is perfluorooctanesulfonate. This substance is an anthropogenic fluorosurfactant that is considered a pollutant. Earlier, this substance was the key ingredient in Scotchgard (a type of fabric protector made by 3M). Later, it was added to the Stockholm Convention on President Organic Pollutants (May 2009).

Figure 02: The Chemical Structure of PFOS

We can produce PFOS industrially, or it comes as a result of the degradation of precursors. So far, the level of PFOS detected in wildlife can cause a considerable health effect, and it can also cause chronic kidney diseases.

The chemical formula for PFOS is C8HF17O3S, and the molar mass is 500 g/mol. There are subunits of C8F17 in PFOS that are hydrophobic and lipophobic. This property is similar to other fluorocarbons. However, it also has sulfonic acid groups or sulfonates, which are polar. Besides, PFOS is an exceptionally stable compound in industries and in the environment due to the effects coming from aggregate carbon-fluorine bonds. Furthermore, it is a fluorosurfactant that can effectively lower the surface tension of water compared to hydrocarbon surfactants.

What is the Difference Between PFOA and PFOS?

Perfluorooctanoic acid or PFOA id a type of perfluorinated carboxylic acid having the chemical formula C8HF15O2 while PFOS stands for perfluorooctanesulfonic acid. The key difference between PFOA and PFOS is that PFOA has a carboxylic functional group, whereas PFOS has a sulfonic functional group.

The following infographic lists the differences between PFOA and PFOS in tabular form.

Summary – PFOA vs PFOS

PFOA and PFOS are organofluorine compounds. PFOA stands for perfluorooctanoic acid while PFOS stands for perfluorooctanesulfonic acid. The key difference between PFOA and PFOS is that PFOA has a carboxylic functional group, whereas PFOS has a sulfonic functional group.

Reference:

1. “Fact Sheets – PFOS and PFOA.” Fact Sheets.

Image Courtesy:

1. “Perfluorooctanoic acid” By Edgar181 – Own work (Public Domain) via Commons Wikimedia
2. “Perfluorooctanesulfonic acid” By Leyo – Own work (Public Domain) via Commons Wikimedia