All About Hydrogen Bonding

The development of hydrogen bonds, an unique category of attractive intermolecular forces emerging from the dipole-dipole interaction between a hydrogen atom bonded with a very strong electronegative atom and another extremely strong atom at -electronegative nearby, is referred to as hydrogen bonding. Hydrogen is held together in water molecules (H₂O) by an electronegative oxygen atom. As a result of the dipole-dipole interaction between the hydrogen atom of one water molecule and the oxygen atom of another H₂O molecule, hydrogen bonding occurs.

What Is Hydrogen Bonding And How Does It Work?

It is the formation of Hydrogen bonds that is the subject of this article. Hydrogen bonds are a special class of attractive intermolecular forces that arise as a result of the dipole-dipole interaction between a hydrogen atom that is bonded to another highly electronegative atom and another highly electronegative atom that is located in the vicinity of the hydrogen atom (also referred to as hydrogen bonding). Hydrogen atoms in water molecules (H₂O) are covalently bound to the more electronegative oxygen atoms, for example. Water molecules are formed as a result of the dipole-dipole interactions between the hydrogen atoms in one water molecule and the oxygen atoms in another H₂O molecule, which results in the formation of hydrogen bonds.

The placement of the bond pair of electrons in the oxygen-hydrogen bond is extremely close to the oxygen nucleus in this case (due to the large difference in the electronegativities of oxygen and hydrogen). So the oxygen atom acquires some negative charge (-) and the hydrogen atom acquires some positive charge (+) in the process. As a result of the electrostatic attraction between the hydrogen atom of one water molecule (which has a positive charge) and the oxygen atom of another water molecule (which has a negative charge), hydrogen bonding can occur. The result of this is that hydrogen bonds are a very specific type of intermolecular attractive force that can only be found in compounds that contain hydrogen atoms that are chemically bound to a very electronegative atom. In comparison to the conventional dipole-dipole and dispersion forces, hydrogen bonds are significantly stronger. When compared to actual covalent or ionic bonds, they are, on the other hand, very weak.

What Are the Prerequisites For Hydrogen Bonding To Occur?

When a hydrogen atom is coupled to a highly electronegative atom, it attracts the shared pair of electrons more strongly, causing this end of the molecule to become slightly negative while the other end of the molecule becomes slightly positive. When the negative end of one molecule attracts the positive end of the other, they establish a weak bond that is not strong enough to hold the other molecule together. The hydrogen bond is the name given to this type of bond.

In the process of hydrogen bonding, one hydrogen atom unites two electronegative atoms at the same time, one of which is linked by a covalent connection and the other which is tied together by a hydrogen bond. The following are the criteria for hydrogen bonding:

The molecule must have at least one atom that is substantially electronegative in relation to the hydrogen atom. The more the electronegativity of the molecule, the greater the polarisation of the molecule.

In order to be effective, the electronegative atom must be tiny in size. The greater the electrostatic attraction, the smaller the size of the object.

The Influence of Hydrogen Bonding

Association of Elements

Because of the hydrogen interaction between the molecules of carboxylic acids, they exist as dimers. Molecular masses of such compounds are found to be double those predicted by their simple formula, indicating that they are more complex.

Dissociation

While in solution, hydrogen fluoride (HF) dissociates and releases the difluoride ion instead of the fluoride ion. This is related to the hydrogen bonding that occurs in HF (hydrogen peroxide). Hydrogen bonds are not formed between the molecules of HCl, HBr, and HI. This explains why certain chemicals, such as KHCl₂, KHBr₂, and KHI₂, do not exist.

Hydrogen Bonding in Water

Hydrogen Bonding in Water is a phenomenon that occurs when two atoms of hydrogen bond together.

A water molecule has an oxygen atom that is extremely electronegative and is connected to a hydrogen atom. In addition, because the oxygen atom is more attracted to the shared pair of electrons, this end of the molecule becomes negatively charged, while the hydrogen atoms become positively charged.

Conclusion

Lower alcohols are more soluble in water than higher alcohols because of the hydrogen bonding that can occur between the water molecule and the alcohol molecule.

Volatility: Because the compounds involving hydrogen bonding between distinct molecules have a greater boiling point than other compounds, they are less volatile than other compounds.

Viscosity and surface tension: The substances that contain hydrogen bonding exist as a molecule that is associated with the substance that contains hydrogen bonding. As a result, their flow becomes more difficult to manage than normal. Higher viscosity and surface tension are seen in these materials.

A result of the decreased density of ice compared to water: In the case of solid ice, hydrogen bonding causes the water molecules to form a cage-like structure. Indeed, each water molecule is tetrahedral to four other water molecules, forming a network of interconnectedness. It is not as tightly packed as it is in a liquid state, which is due to the fact that the molecules are smaller. This case-like structure collapses when ice melts, causing the molecules to become closer to one another. This results in decreased volume and increased density for a given mass of water in this situation. Consequently, at 273 degrees Celsius, ice is denser than water. Ice floats because of this.