Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Strong, Yet Gentle, Acid Uncovered

16.11.2004


Carborane, part of the world’s strongest acid. [Atom color code: orange = boron, gray = carbon, green = chlorine, white = hydrogen.]


New Acid Has Potential to Help With a Variety of Processes

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.

So how can an acid be both strong and gentle? The answer lies in the way chemists define the strength of an acid. Acid strength is the ability of an acid to add a hydrogen ion (H ) to basic molecules. On the other hand, corrosiveness has a lot to do with the nature of the negatively charged part of an acid that always accompanies H .



For example, hydrofluoric acid (chemical formula HF) dissolves glass because the fluoride (F) part of the acid attacks the silicon atom in silica glass at the same time that H attacks an oxygen atom, according to UC Riverside Distinguished Professor of Chemistry, Christopher Reed one of the authors of the findings.

Another example is the choice of an acid to clean lime deposits from inside a copper kettle, he pointed out. The wise homeowner chooses hydrochloric acid not nitric acid because the chlorine part of hydrochloric acid does not attack copper whereas the nitrate part of nitric acid would dissolve the kettle in a mess of toxic brown fumes.

The findings were published in the Oct. 11 issue of Angewandte Chemie in a paper titled “The Strongest Isolable Acid,” co-authored with Reed, UCR Colleagues Mark Juhasz, Stephan Hoffmann and Kee-Chan Kim, and Evgenii Stoyanov of the Boreskov Institute of Catalysis in Novosibirsk, Russia.

The new “strong-yet-gentle” acids are called carborane acids. The secret to their strength is twofold. Most importantly, the carborane part of the acid is an extremely weak base (i.e. weakly alkaline), weaker than the fluorosulfate part of fluorosulfuric acid, which was the previous record holder for the strongest acid. Secondly, carboranes have extraordinary 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 Reed. 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. As a result, carborane acids can add hydrogen ions to weakly basic molecules without destroying the often delicate positively charged molecules that are formed.This is the essence of their strong-yet-gentle qualities, Reed added.

Examples of molecules that add a hydrogen ion and are stabilized with a carborane as the negatively charged part of the product include benzene to give benzenium ion, C60 to give “protonated buckyball,” and alkenes to give carbocations.

None of these positively charged molecules had been “put in a bottle” at room temperature before because the acids used previously would decompose them. The strong-yet-gentle carborane acids overcome this difficulty, allowing chemists to take a closer look at important molecules whose existence was typically fleeting, Reed said. Acidified molecules are important short-lived intermediates in a huge variety of acid-catalyzed chemical transformations including the digestion of food, gasoline improvement, polymer formation and the synthesis of pharmaceuticals.

How strong are carborane acids? 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. Acidic media having or exceeding the acidity of carborane acids had been achieved previously by adding antimony pentafluoride (SbF5) to fluorosulfuric acid but these mixtures are very corrosive and have other limitations.

Acids that are this strong are called superacids and they react with hydrocarbons from oil in a process called hydrocarbon cracking. This is an important process for raising the octane levels of gasoline. The new acids could become very important for understanding and improving this process, Reed said. The 1994 Nobel Prize in Chemistry was awarded to George Olah at USC for his pioneering studies in this field. Carborane acids have advanced this field even further.

There are many other molecules whose reactions with traditional acids are messy and therefore not very useful. Carborane acids deliver very clean acidity without ferocity. Thus, cleaner acid-catalysis of reactions important to the manufacture of pharmaceutical drugs and petroleum products should be possible. Also, there are atoms such as the element Xenon (symbol Xe), which have so far resisted reaction with acid. Reed and his research group want to add hydrogen ions to Xe atoms “because it’s never been done before.”
Reed says, “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.”

Ricardo Duran | EurekAlert!
Further information:
http://www.ucr.edu

More articles from Life Sciences:

nachricht Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY

nachricht NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>