Question

Stearic acid and polyethylene glycol react to form which one of the following soap/s detergents?

• A. Cationic detergent
• B. Soap
• C. Anionic detergent
• D. Non-ionic detergent

Answer 1

The Correct Option is D

To understand which type of detergent is formed from the reaction of stearic acid and polyethylene glycol, let's first analyze the components involved:

1. Stearic Acid: This is a saturated fatty acid commonly found in soaps and detergents. It contains a long hydrophobic hydrocarbon chain and a hydrophilic carboxylic acid group.
2. Polyethylene Glycol (PEG): PEG is a polymer that is non-ionic, meaning it does not carry any charge. It is often used in the production of non-ionic surfactants.

When stearic acid reacts with polyethylene glycol, the hydroxy groups of PEG can form ester linkages with the carboxylic group of stearic acid. This results in a compound that contains no ionic groups (neither cationic nor anionic), making it a non-ionic detergent.

Let's analyze the options:

• Cationic Detergents: These contain positively charged head groups. Given that stearic acid and polyethylene glycol do not provide any ionic character, this option is incorrect.
• Soap: Traditional soaps are typically salts of fatty acids (contain charged groups). Stearic acid with PEG would not form a typical soap due to the absence of a metal cation, making this option incorrect.
• Anionic Detergents: These contain negatively charged head groups. Again, since no such group is formed from the reaction of stearic acid and polyethylene glycol, this option is incorrect.
• Non-Ionic Detergents: These detergents do not have any charged groups, which is exactly the case when stearic acid reacts with polyethylene glycol. Thus, this is the correct answer.

Therefore, the reaction between stearic acid and polyethylene glycol forms a non-ionic detergent.