Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Chemists in Bochum report in Science: Formation of the smallest droplet of acid

19.06.2009
New reaction mechanism at ultracold temperatures
4 water molecules and one HCl are enough

Exactly four water molecules and one hydrogen chloride molecule are necessary to form the smallest droplet of acid. This was the result of work by the groups of Prof. Dr. Martina Havenith (physical chemistry) and Prof. Dr. Dominik Marx (theoretical chemistry) within the research group FOR 618.

They have carried out experiments at ultracold temperatures close to absolute zero temperature using infrared laser spectroscopy to monitor the molecules. This has been accompanied by theoretical ab initio simulations.

According to their calculations, the reaction at these extremely cold temperatures is only possible if the molecules are aggregating one after the other. Their results will be published in the newest issue of "Science".

Chemistry at ultracold temperatures in space

If you put a classical acid, for example hydrogen chloride in water, the acid molecules will preferentially lose a proton (H+). Thereby the pH-value of the solution is decreased and the solution becomes acidic. In particular, so-called hydronium ions (H3O+), are formed by protonated water molecules. This hydronium ion is an important ingredient in many chemical reactions. Despite of the fact that this is one of the most fundamental reactions, it was not clear until now how many water molecules are actually required in order to form a charge separated negative Cl- ion and a positive H3O+ ion. "Whereas we all know acids from our daily life, we have now been able to observe for the first time acid formation on a molecular level." "We will need this knowledge in order to understant chemical processes on nanoscopic structures, on small particles and on surfaces", explains Prof. Havenith-Newen. This indicates that there is a rich chemistry even at very low temperatures; a fundamental basis for reactions within stratospheric clouds or in interstellar media. Previously, it had been unclear whether reactions with only a few water molecules can take place at theses ultracold temperatures.

Ultracold trap

For their experiments, the researchers have successively embedded hydrogen chloride as well as single water molecules in a special ultracold trap. They used nanodroplets of suprafluid helium which have a temperature of less than -272,8 °C. Molecules will first be cooled down before they have a chance to aggregate. "Suprafluid" is a special property of the helium which implies that the embedded molecules are still free to rotate before they are frozen, thereby allowing monitoring with unsurpassed precision. Captured in such a way, it is possible to obtain the chemical fingerprint of the acid ? its infrared spectrum. By combining trapping with high resolution IR laser spectroscopy and theoretical calculations, the chemists demonstrated that exactly four water molecules are required to form the smallest droplet of acid: (H3O)+(H2O)3Cl-.

Important: One molecule after the other

After these results, the researchers were left with the question of how this reaction can take place at ultracold temperatures near absolute zero. "Usually, activation of chemical reactions requires the input of energy, just like for cooking at home you need a cooking plate or a gas flame" explains Prof. Marx. "However, how should this be possible at a few Kelvin (close to absolute zero)?" The calculations, in combination with experiment, showed that the reaction is only possible by a successive aggregation process. Instead of putting together 4 water molecules and an HCl molecule simultanesously at the beginning and the waiting for a dissociation process to occur, they found in their simulations that when adding the water molecules step by step, a proton is transferred exactly when adding the fourth water molecule. Then, a hydronium ion will immediately form with one of the four added water molecules. This unusual mechanism is called "aggregation induced dissociation". "We suspect that such aggregation induced reactions, can explain chemical transformations at ultracold conditions, such as can be found at small ice particles in clouds and in interstellar media", explains Prof. Marx.

Financial support by the German Science Foundation (DFG)

The work which described here is part of the research unit FOR 618 "Understanding the Aggregation of Small Molecules with Precise Methods - Interplay between Experiment and Theory"( Co-ordinator: Prof. Dr. Wolfram Sander (Faculty of Chemistry and Biochemistry) which has been funded by the Germany Science Foundation and which has just been extended for three more years after successful evaluation.

Title

Anna Gutberlet, et al.: Below 1 K: The Smallest Droplet of Acid Aggregation-Induced Dissociation of HCl(H2O)4. In: Science 324, 1545 (2009); DOI: 10.1126/science.1171753

Further information

Prof. Dr. Martina Havenith, Fakultät für Chemie und Biochemie der Ruhr-Universität Bochum, Tel. 0234/32-24249, Fax: 0234/32-14183

martina.havenith@ruhr-uni-bochum.de

Prof. Dr. Dominik Marx, Lehrstuhl für Theoretische Chemie der Ruhr-Universität Bochum, 44780 Bochum, Tel. 0234/32-28083

dominik.marx@theochem.rub.de

Dr. Josef König | idw
Further information:
http://www.ruhr-uni-bochum.de

More articles from Life Sciences:

nachricht Could this protein protect people against coronary artery disease?
17.11.2017 | University of North Carolina Health Care

nachricht Microbial resident enables beetles to feed on a leafy diet
17.11.2017 | Max-Planck-Institut für chemische Ökologie

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>