Researchers have investigated for the first time how two different forms of água (ortho- and para-) behave differently when undergoing chemical reactions.
Água is a chemical entity, a molecule in which a single oxigênio atom is linked to two hydrogen atoms (H2O). Água exists as liquid, solid (ice) and gas (vapours). It is among the few chemicals which do not contain carbono and still can be liquid at room temperature (about 20 degrees). Água is ubiquitous and important for life. At the molecular level it is well known that everyday água exists in two different forms but this information is not of common knowledge. These two forms of água are called isomers and are referred to as ortho- or para- água. 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.
Em um estudo recente publicado em Natureza Communications, researchers from the University of Basel, Hamburg have for the first time investigated the difference in chemical reactivity of these two forms of água 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 água 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- água reacts around 25 percent faster than ortho-water and its able to attract to a reação parceiro mais fortemente. Isso é definitivamente explicado pela diferença no spin nuclear que influencia a rotação das moléculas de água. Além disso, o campo elétrico da para-água é capaz de atrair os íons mais rapidamente. O grupo realizou simulações de computador de moléculas de água para corroborar suas descobertas. Todos os experimentos foram feitos com moléculas em configurações de temperatura muito baixa de quase -273 graus Celsius. Este é um fator importante, conforme explicado pelos autores, que apenas em tais condições os estados quânticos individuais e o conteúdo de energia das moléculas podem ser bem definidos e melhor controlados. O que significa que a molécula de água se estabiliza em qualquer uma de suas duas formas e suas diferenças tornam-se óbvias e claras. Assim, a investigação de reações químicas pode revelar mecanismos e dinâmicas subjacentes que levam a um melhor entendimento. No entanto, o uso prático deste estudo pode não ser muito alto neste momento.
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Fontes)
Kilaj A et al 2018. Observação de diferentes reatividades de para e orto-água para íons diazenilium aprisionados. Natureza das Comunicações. 9 (1). https://doi.org/10.1038/s41467-018-04483-3
