Superacids

The concept of superacids was a new on to me until the other day when I read about a chemistry competition that had been held in Moscow earlier this summer. You may have been in this very competition so, if you had, and I get something wrong, please do put me right!

The competition asked students to ‘design’ (on paper) an alien blood that resembled the blood in the ‘Alien’ movies. If you recall, this blood needed to be capable of dissolving gases (presumably oxygen, so that the alien could respire) but was also extremely acidic—acidic enough to corrode all (or nearly all) metals. I’m not sure how the aliens ‘blood’ vessels didn’t react with this acid…but that is another story.

What did catch my eye was this concept of a really strong acid—a super acid. You may think concentrated sulfuric acid is strong but this type of acid would make the sulfuric acid look like a glass of water (by the way, concentrated sulfuric acid has a pH of 7. Why?)

A little bit of research led me to some very interesting Wikipedia articles on super acids.

Some examples of these commercially available superacids are trifluoromethanesulfonic acid (CF₃SO₃H) and fluorosulfuric acid (HSO₃F). Both acids are supposedly over 1,000 times stronger than the equivalent concentration of sulfuric acid¹.

Trifluoromethanesulfonic acid is used as a catalyst for esterification reactions and has been with us for approximately 70 years.

Source: Jü © (CC BY-SA 4.0), via Wikimedia

Flurosulfuric acid has the following formula and structure:

Source: Wikimedia

There doesn’t seem to be that much use to this acid! It is used to regenerate HF and H₂SO₄ which are used to etch glass and possibly to isomerize alkanes (although there seems to be no commercial use to this reaction).²

In general, the use of superacids seems quite limited. They are used in the polymerization of plastics and the production of high octane gasoline, but presumably this useage is limited as they are so reactive.³ It does beg the question as to what are they stored in…but that is a question for another day.

I did find the following clip on YouTube: https://www.youtube.com/watch?v=cTLBrqcuLBU, supposedly showing the reaction of an orange with chlorosulfonic acid but cannot verify this clip—that said, the reaction is pretty dramatic!

Do you know about superacids? Have you heard of them? How are they used or found? As ever, I would love to hear your ideas and suggestions so please feel free to post them below.

¹ https://en.wikipedia.org/wiki/Superacid

² https://en.wikipedia.org/wiki/Fluorosulfuric_acid. ccessed 7th December 2017

³ https://www.quora.com/What-are-some-common-uses-of-superacids. 

All accessed 7th December 2017