Carbon Allotropes and Cleansing Action of Surfactants

Carbon has an atomic number of 6. It has an electronic configuration of 2,4. The inert gas electronic configuration requires four electrons. However, carbon cannot form an ionic bond. It could gain four electrons, resulting in a C4^– cation formation. However, holding ten electrons would be difficult for the nucleus with six protons. It may lose four electrons, resulting in C4⁺ cations. However, removing four electrons requires a significant amount of energy. Carbon solves this problem by sharing its valence electrons with other carbon atoms or atoms of other elements.

The existence of such a large number of organic compounds is due to carbon’s versatile nature,

• Catenation
• Tetravalent nature

Catenation is the self-linking property of an element, primarily a carbon atom, via covalent bonds to form long straight, branched, and rings of varying sizes.

This characteristic is due to

• The carbon atom’s small size.
• The carbon-carbon bond’s incredible strength.
• Carbon can also form stable multiple bonds (double or triple) with itself and other elements’ atoms.

Tetravalent Carbon has a valency of four in nature. It can form single covalent bonds and double or triple bonds with four other carbon atoms or some other heteroatoms.

Carbon Allotropes

Allotropy refers to the phenomenon in which an element exists in two or more different physical states with similar chemical properties.

There are three major allotropes of carbon.

Diamond: In this, a carbon atom is bonded to four other carbon atoms to form three-dimensional structures. It is the hardest and most insulating substance. It is used for drilling and cutting rocks. It’s also used to make jewellery.

Graphite: Each carbon atom in this material is bonded to three other carbon atoms. It is a good electrical conductor and is used as a lubricant.

Fullerene: It is a carbon-containing cluster of 60 carbon atoms joined together to form spherical molecules. At room temperature, it is a dark solid.

Cleansing Action of Surfactants

Soap is a sodium or potassium salt of long-chain fatty acids.

RCOO^– Na⁺ is the general formula.

Detergent refers to the ammonium and sulphonate salts of long-chain fatty acids.

CH₃—(CH₂)₁₁—C₆H₄—SO₃Na is an example.

Surfactants are substances that reduce the surface tension (or interfacial tension) between two liquids, a gas and a liquid, or a liquid and a solid. Surfactants can be classified as detergents, wetting agents, emulsifiers, foaming agents, or dispersants.

Soaps, detergents and surfactants all have two parts. A long hydrocarbon part that is hydrophobic (repels water) and a short ionic part that is hydrophilic (attracts water).

The hydrocarbon end of the soap molecule attaches to the oily (dirt) drop, while the ionic end orients itself towards the water and forms a spherical structure known as micelles. The soap micelles aid in the dissolution of dirt in water and washing our clothes.

Surfactants form aggregates, such as micelles, in the bulk aqueous phase, with the hydrophobic tails forming the core of the aggregate and the hydrophilic heads in contact with the surrounding liquid. Other types of aggregates, such as spherical or cylindrical micelles or lipid bilayers, can also form. The shape of the aggregates is determined by the chemical structure of the surfactants, specifically the size balance between the hydrophilic head and the hydrophobic tail. The hydrophilic-lipophilic balance is one indicator of this (HLB). Surfactants lower water surface tension by adsorbing at the liquid-air interface. The Gibbs isotherm is the relationship that connects surface tension and surface excess.

The dynamics of surfactant adsorption are critical for practical applications such as foaming, emulsifying, or coating processes, where bubbles or drops must be stabilised quickly. The surfactant’s diffusion coefficient determines the dynamics of absorption. The diffusion of the surfactant to the interface limits adsorption as the interface is formed. An energetic barrier to surfactant adsorption or desorption may exist in some cases. The dynamics are said to be ‘kinetically limited’ if such a barrier limits the adsorption rate. Steric or electrostatic repulsions can cause such energy barriers. The surface rheology of surfactant layers, including the layer’s elasticity and viscosity, is critical in the stability of foams and emulsions.