Question

Which of the following is an Anionic detergent? [2016] (a) Glycerol oleate (b) Sodium lauryl sulphate (c) Cetyl trimethyl ammonium bromide (d) Sodium Stearate

Short answer

The anionic detergent is Sodium lauryl sulphate (option b).

Step-by-step solution

Understand the Definition of Anionic Detergent

Anionic detergents are a class of synthetic detergents in which the largest part of the molecule is an anion, typically consisting of an alkyl sulfate or alkylbenzene sulfonate group. These detergents are often used in household cleaning products.

Analyze Each Option

Look at each option to identify which one matches the properties of an anionic detergent. - Glycerol oleate is an ester of glycerol and oleic acid, and it's not primarily anionic. - Sodium lauryl sulphate (SLS) is a typical anionic detergent, composed of a long alkyl chain attached to a sulfate group. - Cetyl trimethyl ammonium bromide is a cationic detergent, as it contains a positively charged nitrogen atom. - Sodium Stearate is typically used in soaps, not detergents, and can be considered an ionic compound but not a synthetic anionic detergent.

Identify the Anionic Detergent

Sodium lauryl sulphate (option b) fits the criteria for an anionic detergent as it contains a sulfate group linked to a long hydrophobic chain, making it the typical example of an anionic detergent used in multiple cleaning applications.

Key concepts

Sodium Lauryl Sulphate

Sodium Lauryl Sulphate, commonly abbreviated as SLS, is a well-known example of an anionic detergent. This compound features a long hydrophobic chain, which allows it to interact effectively with oils and grease, making it an excellent cleaning agent. The key characteristic of SLS is the sulfate group (-SO₄) attached to a lauryl (12-carbon) chain.
SLS is widely used in a variety of cleaning products including shampoos, shower gels, and household cleaning liquids. Its ability to produce a rich lather and effectively emulsify and remove dirt contributes to its popularity. Due to its effectiveness, SLS is also employed in certain industrial cleaning agents.

Synthetic Detergents

Synthetic detergents are man-made cleaning agents specifically designed to function in various types of water conditions. Unlike traditional soaps, synthetic detergents do not form scum in hard water. Such detergents are composed of different molecular structures that break down dirt and oils, with an emphasis on being adaptable to modern water supply variations.
The creation of synthetic detergents was a significant advancement in cleansing technology and includes several categories, one of which is anionic detergents, to which Sodium Lauryl Sulphate belongs. These detergents offer enhanced cleaning properties and extreme versatility, which contribute to their widespread usage. They are formulated with specific additives to target different cleaning needs from household to industrial environments.

Alkyl Sulfate Group

The alkyl sulfate group is a crucial chemical structure found in many anionic detergents. These molecules consist of an alkyl group, usually a long carbon chain, attached to a sulfate group. This unique structure allows such compounds to successfully interact with water and dirt. The sulfate part is hydrophilic, meaning it attracts water, while the alkyl chain is hydrophobic and interacts with oils.
Sodium Lauryl Sulphate is a perfect embodiment of the alkyl sulfate group. This dual characteristic allows it to act as a bridge between water and oil, significantly aiding in the emulsification process. The alkyl sulfate group’s ability to lower water's surface tension is a major reason for its effectiveness, enhancing the cleaning power of detergents they comprise.