Researchers have investigated for the first time how two different forms of Wasser (ortho- and para-) behave differently when undergoing chemical reactions.
Wasser is a chemical entity, a molecule in which a single Sauerstoff atom is linked to two hydrogen atoms (H2O). Wasser exists as liquid, solid (ice) and gas (vapours). It is among the few chemicals which do not contain Kohlenstoff and still can be liquid at room temperature (about 20 degrees). Wasser is ubiquitous and important for life. At the molecular level it is well known that everyday Wasser exists in two different forms but this information is not of common knowledge. These two forms of Wasser are called isomers and are referred to as ortho- or para- Wasser. The main difference between these forms is very subtle and is simply the relative orientation of the nuclear spins of the two hydrogen atoms which are aligned in either same or opposite direction, hence their names. This spin of hydrogen atoms is due to atomic physics though this phenomenon is not yet fully understood. These two forms have identical physical properties and it has been believed so far that they should also then have identical chemical properties.
In einer kürzlich veröffentlichten Studie in Natur Communications, researchers from the University of Basel, Hamburg have for the first time investigated the difference in chemical reactivity of these two forms of Wasser and have proven that ortho- and para- forms react very differently. Chemical reactivity means the way or the ability by which a molecule undergoes a chemical reaction. The study involved separation of Wasser into its two isomeric forms (ortho- and para-) using an electrostatic deflector by involving electric fields. Since both these isomers are practically the same and have identical physical properties, this separation process is complex and challenging. The separation was achieved by this group of researchers by using a method based of electric fields developed by them for Free-Electron Laser Science. The deflector introduces an electric field to a beam of atomized water. Since there is crucial difference in nuclear spin in the two isomers, this slightly impacts the way by which atoms interact with this electric field. Therefore, as the water travels through the deflector it starts separating into its two forms ortho- and para-.
Researchers have demonstrated that para- Wasser reacts around 25 percent faster than ortho-water and its able to attract to a Reaktion Partner stärker. Dies erklärt sich definitiv durch den Unterschied im Kernspin, der die Rotation der Wassermoleküle beeinflusst. Außerdem kann das elektrische Feld des Parawassers die Ionen schneller anziehen. Die Gruppe führte außerdem Computersimulationen von Wassermolekülen durch, um ihre Ergebnisse zu untermauern. Alle Experimente wurden mit Molekülen bei sehr niedrigen Temperatureinstellungen von fast -273 Grad Celsius durchgeführt. Dies ist ein wichtiger Faktor, wie die Autoren erklären, dass nur unter solchen Bedingungen die einzelnen Quantenzustände und der Energiegehalt von Molekülen gut definiert und besser kontrolliert werden können. Das bedeutet, dass sich das Wassermolekül in einer seiner beiden Formen stabilisiert und ihre Unterschiede offensichtlich und deutlich werden. Die Untersuchung chemischer Reaktionen kann daher zugrunde liegende Mechanismen und Dynamiken aufdecken, die zu einem besseren Verständnis führen. Der praktische Nutzen dieser Studie dürfte derzeit jedoch nicht sehr hoch sein.
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Quelle (n)
Kilaj A et al 2018. Beobachtung verschiedener Reaktivitäten von para- und ortho-Wasser gegenüber eingefangenen Diazenyliumionen. Nature Communications veröffentlicht . 9(1). https://doi.org/10.1038/s41467-018-04483-3
