Scientists from the University of Basel in Switzerland have found an anomalous property in water, which means that some of its molecules (para-isomers) react better than others (ortho-isomers). The researchers' article was published in the journal Nature Communications. This is reported by Science Alert.
The water molecule exists in two forms - ortho- (o-) and para-water (p-water), which differ from each other by the value of the total nuclear spin, which is made up of the spins of the hydrogen nuclei that make up the molecule. For o-water, it is equal to one, and for p-water - zero. Spin cannot change in isolated molecules, it is also preserved in collisions with other molecules and even in chemical reactions. Differences in spins affect rotational symmetry, so the p-water molecule will be symmetric, and o-water - antisymmetric (a full revolution is required to return to its original state). However, until now it was not known whether spins can determine the different chemical properties of o- and p-water.
The researchers created a dusty plasma crystal in an ion trap from calcium and diazenilium ions (N2H +) and tracked how various forms of water react with it. Because the para-isomers deflect more strongly in the electrostatic field due to their significant dipole moment, this allowed scientists to separate the two forms of water from each other. Then the crystal was bombarded with water molecules, and by the amount of remaining diazelinium ions, the researchers determined which isomer reacted best with the crystal.
It turned out that the rotational symmetry of the para-water molecules made them 23 percent more reactive than ortho-water. Thus, it was demonstrated for the first time that the chemical reaction of polyatomic molecules with ions depends on rotational symmetry.