World's Strongest and Kindest Acid Discovered

By Roland Piquepaille

Researchers at the University of California, Riverside (UCR), have discovered the world's strongest acid, according to Nature. It's a million times stronger than concentrated sulfuric acid and about a billion times stronger than the acids found in your stomach. But surprisingly, it's also one of the least corrosive. So you might soon find one of these new carborane acids, or superacids, in vitamins bought at your local drugstore. Even if this is not appealing to you, these researchers have other projects. They want to have fun by building molecules that have never been made before. Read more...

This new superacid is even better described in this UCR news release. Let's start with the introduction.

Researchers at the University of California, Riverside have discovered the world's strongest acid. Remarkably it is also the gentlest acid. This non-toxic and non-corrosive acid may have a role in processes such as improving the quality of gasoline, developing polymers and synthesizing pharmaceuticals.

The most important characteristic of these carborane acids is that they have anextraordinary chemical stability.

They have an icosahedral arrangement of eleven boron atoms plus one carbon atom, which is probably the most chemically stable cluster of atoms in all of chemistry, according to Christopher Reed, UC Riverside Distinguished Professor of Chemistry. This means that the carborane part of the acid cannot participate in the chemistry of corrosion and decomposition that fluoride and nitrate show in hydrofluoric acid and nitric acid.

	Here is a diagram of the CHB11R5X6 carborane ions (Credit: UCR).
	And here is another diagram showing the structure of the carborane, part of the world's strongest acid. [Atom color code: orange = boron, gray = carbon, green = chlorine, white = hydrogen.] (Credit: UCR).

Now, how strong are these superacids?

The strongest one is at least a million times stronger than concentrated sulfuric acid (H₂SO₄) and hundreds of times stronger than the previous record holder, fluorosulfuric acid (HFSO₃). Concentrated sulfuric acid is already more than a billion times (10¹²) stronger than dilute swimming pool acid or the acid in one's stomach.

Fine, but how can we use these enormously strong acids? They could be used for example in hydrocarbon cracking, a process which raises the octane levels of gasoline.This could be useful, but Nature points to other possible usages.

They allow the production of 'acidified' organic molecules. These are compounds that have had a hydrogen ion added to them, as in the case of many vitamins in over-the-counter supplements.

Acidified compounds occur fleetingly in the digestion of food, petroleum refinement and drug manufacture, says Reed. Carborane acids could be used to study these elusive chemicals more closely, or even help chemical industries to run their reactions more efficiently.

But even more importantly, these researchers want more to have fun than to make money.

But the researchers' immediate goal would be less of a money-spinner. They want to use carborane acids to acidify atoms of the inert gas xenon, simply because, they say, "it's never been done before".

And in the UCR news release, Reed adds the following.

Our research is driven by making molecules that have never been made before. Carborane acids are allowing us to do this. That is the true value of this research. Science gets advanced, and at the same time, students are experiencing the thrill of discovery as they become scientists.

I don't know for you, but the idea of taking vitamins containing such strong acids disturbs me a little.

Anyway, if you want more information before taking your next dietary supplement, the research paper has been published by Angewandte Chemie under the ramarkably simple titlee "The Strongest Isolable Acid." Here are the links to the abstract and to the full paper (PDF format, 4 pages). The diagram of the carborane ions was extracted from this paper.

Sources: Michael Hopkin, Nature, November 16, 2004; University of California, Riverside news release, November 15, 2004; Angewandte Chemie International Edition, Volume 43, Issue 40 , Pages 5352 - 5355, October 5, 2004

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