[ad_1]
Scientists have recently discovered a whole new type of chemical bond – and it’s much stronger than it’s allowed to be.
The new type of bond shows that the fracture between strong covalent bonds, which bind molecules together, and weak hydrogen bonds, which form between molecules and can be broken by something as simple as mixing salt in a glass of water, is not so clear. as the chemistry textbooks suggest.
Think about this high school chemistry class, and you will recall that there are different types of links that bind atoms together into molecules and crystal structures.
Ionic bonds bind metals and non-metals together to form salts. Strong covalent bonds bind molecules like carbon dioxide and water. Much weaker hydrogen bonds form due to some type of electrostatic attraction between hydrogen and a more negatively charged atom or molecule, for example by causing the attraction of water molecules and the formation of droplets or of crystalline ice. Ionic, covalent, and hydrogen bonds are all relatively stable; they tend to last for long periods and have easily seen effects. But researchers have long known that in a chemical reaction, when chemical bonds form or break, the story is more complicated and involves “intermediate states” that can exist for tiny fractions of a second and are more difficult. to observe.
In the new study, the researchers were able to maintain these intermediate states long enough to make a detailed examination. What they found was a hydrogen bond with the strength of a covalent bond, binding the atoms together into something resembling a molecule.
Related: Nobel Prize in Chemistry: 1901-present
To do this, the researchers dissolved a compound of hydrogen fluoride in water and observed how the hydrogen and fluorine the atoms interacted. Fluorine atoms were attracted to hydrogen atoms due to imbalances of positive and negative charges across their surfaces, the classic structure of a hydrogen bond. Each hydrogen atom tended to be sandwiched between two fluorine atoms. But these sandwiches were bonded with more force than the typical hydrogen bonds, which break easily. Hydrogen atoms bounced between fluorine atoms, forming bonds as strong as covalent bonds and resembling molecules, which hydrogen bonds should not be able to form. But the mechanism of the new bond was electrostatic, meaning it involved the kind of positive and negative charge differences that define hydrogen bonds.
The new bonds had a strength of 45.8 kilocalories per mole (a unit of chemical bond energy), higher than some covalent bonds. Nitrogen molecules, for example, are made up of two nitrogen atoms bonded together with a force of around 40 kcal / mol, according to LibreTexts. A hydrogen bond typically has an energy of around 1 to 3 kcal / mol, according to the book Biochemistry.
They described their results in an article published Thursday (January 7) in the journal Science. In an accompaniment item in Science, Mischa Bonn and Johannes Hunger, researchers at the Max Planck Institute for Polymer Research in Germany, who were not involved in the study, wrote that this unusual link blurs the clear categories of chemistry.
“The existence of a covalent-hydrogen bonded hybrid state not only challenges our current understanding of what exactly a chemical bond is, but also provides the opportunity to better understand chemical reactions,” they wrote, “where ‘intermediate reaction states’ are often invoked but rarely directly studied.”
Similar bonds likely exist in pure water, they wrote, when a hydrogen atom becomes sandwiched between two water molecules. But those links are believed to exist but not last as long, the researchers wrote. And they have never been conclusively observed.
This study, they wrote, could open the door to a “deeper understanding of strong bonds” and intermediate reaction states.
Originally posted on Live Science.
[ad_2]
Source link