Many people do not realize that water molecules take on two different forms, yet contain almost identical physical properties. A new study led by the University of Basel is the first to demonstrate that these two different forms of water do not have the same reaction to chemicals.
Water is a molecule comprised of a single oxygen atom linked to two hydrogen atoms. At this molecular level, water exists in two forms, or isomers.
The two hydrogen atoms that make up water spin in a different relative position in one isomer versus the other. Depending on the orientation of the spins, they are referred to as being either ortho- or para-water.
The nearly-identical physical properties of the isotopes make it challenging to separate them. However, thanks to a technique based on electric fields developed by Professor Jochen Küpper from the Hamburg Center for Free-Electron Laser Science, the team succeeded in its observation.
The experts managed to separate the two forms of water to examine how they differ in terms of their chemical reactivity, and found distinctive reactions between them.
The researchers determined that there were controlled reactions between the “pre-sorted” water isomers and ultra-cold protonated nitrogen held in a trap. During this process, a diazenylium ion transfers its proton to a water molecule. This reaction is also observed in the chemistry of interstellar space.
According to the study, para-water reacts about 25 percent faster than ortho-water, which can be explained by the nuclear spin that also impacts the rotation of the water molecules. This means that different attractive forces act between the reaction partners. Para-water is able to attract its reaction partner more strongly than the ortho-form, which leads to an increased chemical reactivity.
“The better one can control the states of the molecules involved in a chemical reaction, the better the underlying mechanisms and dynamics of a reaction can be investigated and understood,” explained study lead author Professor Stefan Willitsch.
The research is published in the journal Nature Communications.
By Chrissy Sexton, Earth.com Staff Writer