Arguably link hydrogen bonding, hydrogen bond in English, is a dipole-dipole force result of the attractive force of a very electronegative atom and a hydrogen atom covalently bonded to another electronegative atom. It can be both intra and intermolecular … blah blah, blah blah, blah blah … but that’s how chemists don’t even know about it.
First, it should be noted that the valence shell of the atoms is a kind of showcase in which each element has the capacity for a certain number of electrons . Only a few privileged ones, the noble gases, have it full – that’s why they don’t join anyone – while the rest try to fill it with more or less energy. The most impetuous –electronegative– of all the elements when filling their valence layer are, in order and by far, fluorine, oxygen and nitrogen. These elements have a lot, a lot, a tendency to pick up electrons from other atoms to complete the eight electrons that go into their showcase. It is a treasure that they want to obtain at almost any price . To do this, on many occasions they are associated, through covalent bonding, to lend each other electrons with other atoms, so that both can show off their full showcase.
Hydrogen looking for its electrons
On the other hand, the hydrogen atom has a small showcase where only two electrons fit , although with only one electron. This single electron, in the covalent bond with one of the aforementioned electronegative elements, is taken from it by the atom of great electronic greed, so that the poor hydrogen is left in practice without any electrons. Hydrogen, which is also electronegative, although less, happens to have a positive partial charge, which for any other element would not be too much, but given the tiny size of hydrogen it is a high charge . Desperate to have an electron in his showcase, a valence shell, to lose its partial positive charge, he reveals himself before the theft suffered and tries to grab electrons in other electronegative atoms, either from the same molecule – intramolecular bond – or from adjacent molecules – intermolecular bond-. This attempt at electron capture is hydrogen bonding, also called a hydrogen bond.
But what is this for? Well, although it seems simple, almost laughable, this link is constituted as a fundamental union for life. For example, thanks to intermolecular hydrogen bonds, the extraordinarily high boiling point of water (100ºC) is explained compared to the most molecularly similar compound that exists, hydrogen sulfide (-60ºC), which is even heavier; or, on the other hand, intramolecular hydrogen bonds are responsible for the internal bonds in the famous structure of DNA, called double helix.
Antonio Jesús Jiménez studies Science and Technology of New Materials at the University of Seville. Article written in collaboration with the UCC + i of the University of Seville.
