Featured Research

from universities, journals, and other organizations

Hot And Cold Moves Of Cyanide And Water: Temperature Determines Which Molecule Rocks Out

Date:
September 14, 2009
Source:
DOE/Pacific Northwest National Laboratory
Summary:
Scientists have long known that molecules dance about as the temperature rises, but now researchers know the exact steps that water takes with a certain molecule. Results with small, electrically charged cyanide ions and water molecules reveal that water zips around ions to a greater extent than expected. The findings improve our understanding of a chemical interaction important in environmental and atmospheric sciences.

Water molecules (red and white) dance around cyanide ions (blue and gray) more actively than previously thought.
Credit: Image courtesy American Chemical Society

Scientists have long known that molecules dance about as the temperature rises, but now researchers know the exact steps that water takes with a certain molecule. Results with small, electrically charged cyanide ions and water molecules reveal that water zips around ions to a greater extent than expected. The findings improve our understanding of a chemical interaction important in environmental and atmospheric sciences.

"One of the cornerstones of Department of Energy nuclear cleanup missions and climate research is a fundamental understanding of water and ions, one of the most common chemical interactions in the environment," said chemist Xue-Bin Wang of the DOE's Pacific Northwest National Laboratory and Washington State University.

"We've developed a new instrument to probe the dynamics of ions in water," Wang said. "And we've combined theory and modeling to make sense of those experiments, giving us a deeper fundamental understanding of what is happening with this ubiquitous molecule – water."

Wang, PNNL physical chemist Sotiris S. Xantheas, physical chemist Lai-Sheng Wang of PNNL and WSU, and their colleagues published the results in the Journal of Physical Chemistry A. The journal featured their work on the cover of its September 3 issue.

Thirst for Details

Environmental scientists want to know how contaminants move through watery environments below ground, and atmospheric scientists want to know how small particles flutter through water vapor in the sky. To get at the basics, they study a simpler interaction: water and ions, small atoms or molecules that have a slight electrical charge and exist everywhere in nature.

For example, when common table salt -- sodium chloride -- dissolves in water, the negatively charged chloride ions (Cl–) and the positively charged sodium ions (Na+) each interact separately with the water molecules.

Previous work with chloride ions and water has yielded conflicting results about how a water molecule (which is shaped like a boomerang) and a chloride ion (shaped like a ball) face each other. Other groups study barbell-shaped cyanide ions because many molecules found naturally in the environment contain cyanide. The chemical interactions of water and either chloride or cyanide are influenced by the charge and the shape of the molecules, as well as the temperature in which they find themselves.

But directly observing temperature's role in how water and cyanide ions interact has been difficult. So, the team developed a unique instrument that allowed them to precisely control the temperature down to almost absolute zero, or the temperature at which everything freezes. The team used "temperature-controlled photoelectron spectroscopy" in EMSL, the DOE's Environmental Molecular Sciences Laboratory on the PNNL campus, to determine how tightly one cyanide ion and one to three water molecules interact at the very low temperature of -438 F (12 Kelvin) and again at ambient temperature of 80 F (equivalent to 300 Kelvin).

Unexplained Energy

The team measured the molecules' "electron binding energy" at low and high temperatures. This energy is an indication of how tightly the molecules hold onto their electrons -- the tighter the hold, the stronger the bonds that will form between molecules. The team found that ones at low temperature exhibited higher electron binding energy than the ones at high temperatures, as they had expected. However, the difference between the two scenarios was greater than the team expected.

To explore the unexpected difference in energy, the researchers ran computer simulations on the Chinook supercomputer in EMSL. This also let them determine how the boomerang-shaped water and barbell-shaped cyanide faced each other. First they estimated how much energy the molecules used to take different configurations. Then they compared the computer-based estimates to the data they collected in their unique instrument at different temperatures.

The team found that the molecules behaved differently at cold and warm temperatures. At lower temperatures, the boomerang-shaped water held still while the cyanide teetered at the end of one of water's two arms. There, the cyanide flipped, sometimes pointing its carbon (C) atom towards the water's arm, and sometimes pointing its nitrogen (N). At the coldest temperature tested, -438 F, the molecules froze, with cyanide pointing its nitrogen end at the water.

Hot to Trot

At ambient temperatures, however, the barbell-shaped cyanide held steady while the water molecule rocked and flipped around the cyanide. Although the researchers were surprised at how much the water moved, the many positions water could take explained why they saw less electron binding energy than they expected at room temperature: A wiggly water means that the bond between molecules isn't that tight.

"Water can interact with cyanide's carbon or nitrogen and rock back and forth on one atom," said Wang. He added that the detail they get with this instrument is impressive. "Scientists have known for years that atoms move around when temperature rises. Now they can determine the most probable position that the molecule is in at different temperatures."

The results also explain the conflicting results with chloride ions and water, the researchers said, because of the importance of temperature on that interaction as well.

The researchers plan to follow up with studies that include many water molecules and ions at once, as well as with more complex ions than cyanide.

Other authors include PNNL's Karol Kowalski and Alfred Laubereau and Jasper Werhahn from the Technical University of Munich at Garching.

This work was supported by the Department of Energy's Office of Basic Energy Sciences within the Office of Science.


Story Source:

The above story is based on materials provided by DOE/Pacific Northwest National Laboratory. Note: Materials may be edited for content and length.


Journal Reference:

  1. Xue-Bin Wang, Jasper C. Werhahn, Lai-Sheng Wang, Karol Kowalski, Alfred Laubereau, and Sotiris S. Xantheas. Observation of a Remarkable Temperature Effect in the Hydrogen Bonding Structure and Dynamics of the CN(H2O) Cluster. The Journal of Physical Chemistry A, 2009; 113 (35): 9579 DOI: 10.1021/jp9034002

Cite This Page:

DOE/Pacific Northwest National Laboratory. "Hot And Cold Moves Of Cyanide And Water: Temperature Determines Which Molecule Rocks Out." ScienceDaily. ScienceDaily, 14 September 2009. <www.sciencedaily.com/releases/2009/09/090903064446.htm>.
DOE/Pacific Northwest National Laboratory. (2009, September 14). Hot And Cold Moves Of Cyanide And Water: Temperature Determines Which Molecule Rocks Out. ScienceDaily. Retrieved July 29, 2014 from www.sciencedaily.com/releases/2009/09/090903064446.htm
DOE/Pacific Northwest National Laboratory. "Hot And Cold Moves Of Cyanide And Water: Temperature Determines Which Molecule Rocks Out." ScienceDaily. www.sciencedaily.com/releases/2009/09/090903064446.htm (accessed July 29, 2014).

Share This




More Matter & Energy News

Tuesday, July 29, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Baluchistan Mining Eyes an Uncertain Future

Baluchistan Mining Eyes an Uncertain Future

AFP (July 29, 2014) Coal mining is one of the major industries in Baluchistan but a lack of infrastructure and frequent accidents mean that the area has yet to hit its potential. Duration: 01:58 Video provided by AFP
Powered by NewsLook.com
Easier Nuclear Construction Promises Fall Short

Easier Nuclear Construction Promises Fall Short

AP (July 29, 2014) The U.S. nuclear industry started building its first new plants using prefabricated Lego-like blocks meant to save time and prevent the cost overruns that crippled the sector decades ago. So far, it's not working. (July 29) Video provided by AP
Powered by NewsLook.com
Lithium Battery 'Holy Grail' Could Provide 4 Times The Power

Lithium Battery 'Holy Grail' Could Provide 4 Times The Power

Newsy (July 28, 2014) Stanford University published its findings for a "pure" lithium ion battery that could have our everyday devices and electric cars running longer. Video provided by Newsy
Powered by NewsLook.com
The Carbon Trap: US Exports Global Warming

The Carbon Trap: US Exports Global Warming

AP (July 28, 2014) AP Investigation: As the Obama administration weans the country off dirty fuels, energy companies are ramping-up overseas coal exports at a heavy price. (July 28) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins