Properties of Hydrogen Bonding

With the simplest atomic structure, H2, hydrogen is the most abundant element in the universe and the third most productive element on Earth’s surface. It is a diatomic molecule in its elemental state, therefore H2. Hydrogen is found widely in the environment, such as in water and the Earth’s crust. It also has isotopes, which are elements from the family of hydrogen with the same number of electrons but a variable number of neutrons. 

Hydrogen bonding is the process of forming hydrogen bonds that are an attractive intermolecular force of a particular class that results from the dipole-dipole interaction between the hydrogen atom and a highly electronegative atom.

What is hydrogen bonding? 

Hydrogen bonding can be described as the development of hydrogen bonds. Hydrogen bonding primarily takes place between an electronegative and a hydrogen atom. Although the hydrogen bond is comparatively weaker, it is stronger than the Van der Waals forces. Many believe the hydrogen bond is a type of weak chemical bond. 

Further, hydrogen bonding is classified into two major parts:

Intermolecular hydrogen bonding: Intermolecular hydrogen bonding can be defined as when the hydrogen bonding takes place between different molecules that have either the same or other compounds. The most common examples are hydrogen bonding in alcohol, water, and ammonia. 

Intramolecular hydrogen bonding: Intramolecular hydrogen bonding can be defined as hydrogen bonding that takes place within the molecule only. It mainly occurs in compounds that have two groups (one of the hydrogen atom and highly electronegative atom.) 

Properties of the hydrogen bonding 

The following are the properties of hydrogen bonding.

• Volatility: Hydrogen bonding is less volatile as the compounds with hydrogen bonding between several different molecules possess a higher boiling point. 
• Solubility: Since hydrogen bonding can easily take place between alcohol and water molecules, the lower alcohol is more soluble in water.
• The density of ice is lower than that of water: In ice, hydrogen bonding leads to a cage-like structure. However, every water molecule is closely linked to the four water molecules. Since the molecules are in their liquid state, they are not packed closely. As the ice starts to melt, the case-like structure also begins to melt, and all the molecules come closer to one another. As a result, even if the water mass is the same, the density increases and volume decreases.
• Surface tension and viscosity: Substances with hydrogen bonding exist as the associated molecule. Therefore, their flow is way difficult. However, they have more viscosity and surface tension.

Why do hydrogen-bonded compounds have high melting and boiling points? 

Hydrogen-bonded compounds usually feature high boiling and melting points. These elevated temperatures of hydrogen-bonded compounds need more energy to break these bonds. 

• Since there is hydrogen bonding in NH3 and no hydrogen bonding in PH3, ammonia has a high boiling point. 
• When at room temperature, H2O is liquid. However, H2S, H2Se, and H2Te are found in the gaseous state. Since hydrogen bonding gives rise to links in water molecules, it results in higher boiling and melting point if compared to other chemicals. 
• As ethanol has hydrogen bonds, its boiling point is higher than diethyl ether.

Examples of hydrogen bonding 

Hydrogen bonding can be best understood through examples. Here are some common examples of hydrogen bonding:

• Hydrogen bonding in hydrogen fluoride: Since fluorine has the highest value of electronegativity, it leads to the formation of the strongest hydrogen bond.
• Hydrogen bonding in water: A water molecule has a highly electronegative oxygen atom connected to hydrogen atoms. Since the oxygen atom attracts the electron’s shared pair, its end becomes negative, whereas the hydrogen atom becomes positive. 
• Hydrogen bonding in ammonia: It has electronegative atom nitrogen connected to hydrogen atoms. 
• Hydrogen bonding in carboxylic acid and alcohols: Alcohol is referred to as an organic molecule with an -OH group. Generally, in case any molecule that has a hydrogen atom is either linked to nitrogen or oxygen directly. Later, hydrogen bonding becomes easier. 
• Hydrogen bonding in the polymer: In order to determine 3D structures and properties which are acquired by natural and synthetic proteins, hydrogen bonding is a crucial factor. It also plays a significant role to define the cellulose structure along with derived polymers, including flax or cotton. 

Conclusion 

Experts classify hydrogen bonding as a type of weak chemical bond. However, it is generally described as the development of hydrogen bonds that are an attractive intermolecular force’s special class which arises because of the dipole-dipole interaction between the hydrogen atom and highly electronegative atom. 

It is further classified into two major parts, including intermolecular hydrogen bonding and intramolecular hydrogen bonding.