Strange molecule in the sky cleans acid rain

It's the unusual chemistry facilitated by this molecule, however, that will attract the most attention from scientists.

Marsha Lester, the University of Pennsylvania's Edmund J. Kahn Distinguished Professor, and Joseph Francisco, William E. Moore Distinguished Professor of Chemistry at Purdue University, found the molecule, which had puzzled and eluded scientists for more than 40 years.

A technical paper describing the molecule is published this week in a special edition of the Proceedings of the National Academy of Science.

Somewhat like a human body metabolizing food, the Earth's atmosphere has the ability to “burn,” or oxidize pollutants, especially nitric oxides emitted from sources such as factories and automobiles. What doesn't get oxidized in the atmosphere falls back to Earth in the form of acid rain.

“The chemical details of how the atmosphere removes nitric acid have not been clear,” Francisco says. “This gives us important insights into this process. Without that knowledge we really can't understand the conditions under which nitric acid is removed from the atmosphere.”

Francisco says the discovery will allow scientists to better model how pollutants react in the atmosphere and to predict potential outcomes.

“This becomes important in emerging industrial nations such as China, India and Brazil where there are automobiles and factories that are unregulated,” Francisco says. “This chemistry will give us insight into the extent that acid rain will be a future concern.”

Lester says the molecule had been theorized by atmospheric chemists for 40 years and that she and Francisco had pursued it for the past several years.

“We've speculated about this unusual atmospheric species for many years, and then to actually see it and learn about its properties was very exciting,” she says.

What makes the molecule so unusual is its two hydrogen bonds, which are similar to those found in water.

Chemists know that although water is one of the most common substances found on the planet, it has unusual properties. For example, the solid form – ice – is lighter than the liquid form and floats. Water also boils at a much higher temperature than would be expected from its chemical structure.

The cause of these strange behaviors are weak hydrogen bonds that hold water molecules together.

The new atmospheric molecule has two hydrogen bonds, which allows it to form a six-sided ring structure. Hydrogen bonds are usually weaker than the normal bonds between atoms in a molecule, which are known as covalent bonds. In fact, covalent bonds are 20 times stronger than hydrogen bonds. But in this case, these two hydrogen bonds are strong enough to affect atmospheric chemistry, Francisco says.

Lester says the new molecule exhibits its own unusual properties.

“The reaction involving this molecule proceeds faster as you go to lower temperatures, which is the opposite of most chemical reactions,” she says. “The rate of reaction also changes depending on the atmospheric pressure, and most reactions don't depend on external pressure. The molecule also exhibits unusual quantum properties.”

Lester says the unusual properties prevented scientists from being able to model the reaction for so long.

“This is not how we explain chemistry to high school students,” she says.

Francisco says that this discovery will be used in areas other than atmospheric chemistry.

“Here's a situation where we were studying this purely environmental problem, but, because the findings are so fundamental, it may have broader ramifications to biological systems that depend on hydrogen bonds,” he says.

The breakthrough was enabled by laser-based laboratory techniques at the University of Pennsylvania and the supercomputing resources available at Purdue, Francisco says. The computation was done on an SGI Altix supercomputer operated by the Office of Information Technology at Purdue.

“The key is knowing where to look and how to identify new chemical entities, and with the computing resources we have at Purdue we can help identify processes to within experimental uncertainty,” he says. “We couldn't have done this without the supercomputing power that we have available.”

Writer: Steve Tally, (765) 494-9809, tally@purdue.edu
Sources: Joseph Francisco, (765) 494-7851, jfrancis@purdue.edu
Marsha Lester, (215) 898-4640, milester@sas.upenn.edu
Purdue News Service: (765) 494-2096; purduenews@purdue.edu

Media Contact

Steve Tally EurekAlert!

More Information:

http://www.purdue.edu

All latest news from the category: Ecology, The Environment and Conservation

This complex theme deals primarily with interactions between organisms and the environmental factors that impact them, but to a greater extent between individual inanimate environmental factors.

innovations-report offers informative reports and articles on topics such as climate protection, landscape conservation, ecological systems, wildlife and nature parks and ecosystem efficiency and balance.

Back to home

Comments (0)

Write a comment

Newest articles

Lighting up the future

New multidisciplinary research from the University of St Andrews could lead to more efficient televisions, computer screens and lighting. Researchers at the Organic Semiconductor Centre in the School of Physics and…

Researchers crack sugarcane’s complex genetic code

Sweet success: Scientists created a highly accurate reference genome for one of the most important modern crops and found a rare example of how genes confer disease resistance in plants….

Evolution of the most powerful ocean current on Earth

The Antarctic Circumpolar Current plays an important part in global overturning circulation, the exchange of heat and CO2 between the ocean and atmosphere, and the stability of Antarctica’s ice sheets….

Partners & Sponsors