Researchers have investigated for the first time how two different forms of de apă (ortho- and para-) behave differently when undergoing chemical reactions.
Apă is a chemical entity, a molecule in which a single oxigen atom is linked to two hydrogen atoms (H2O). Apă exists as liquid, solid (ice) and gas (vapours). It is among the few chemicals which do not contain carbon and still can be liquid at room temperature (about 20 degrees). Apă is ubiquitous and important for life. At the molecular level it is well known that everyday de apă exists in two different forms but this information is not of common knowledge. These two forms of de apă are called isomers and are referred to as ortho- or para- de apă. 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.
Într-un studiu recent publicat în Natură Communications, researchers from the University of Basel, Hamburg have for the first time investigated the difference in chemical reactivity of these two forms of de apă 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 de apă 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- de apă reacts around 25 percent faster than ortho-water and its able to attract to a reacţie partener mai puternic. Acest lucru se explică cu siguranță prin diferența de spin nuclear care influențează rotația moleculelor de apă. De asemenea, câmpul electric al apei este capabil să atragă ionii mai repede. Grupul a efectuat în continuare simulări computerizate ale moleculelor de apă pentru a-și corobora constatările. Toate experimentele au fost făcute cu molecule la temperaturi foarte scăzute de aproape -273 de grade Celsius. Acesta este un factor important, așa cum au explicat autorii, că numai în astfel de condiții stările cuantice individuale și conținutul de energie al moleculelor pot fi bine definite și mai bine controlate. Ceea ce înseamnă că molecula de apă se stabilizează în oricare dintre cele două forme ale sale, iar diferențele lor devin evidente și clare. Astfel, investigarea reacțiilor chimice poate dezvălui apoi mecanismele și dinamica care stau la baza, care conduc la o mai bună înțelegere. Cu toate acestea, utilizarea practică a acestui studiu ar putea să nu fie foarte mare în acest moment.
***
{Puteți citi lucrarea originală de cercetare făcând clic pe linkul DOI de mai jos în lista surselor citate}
Sursa (s)
Kilaj A et al 2018. Observarea diferitelor reactivități ale apei para și orto față de ionii de diazeniliu prinși. Natura Comunicaţii. 9(1). https://doi.org/10.1038/s41467-018-04483-3
