Question

Which one of the following is a cationic detergent ?

• A. Cetyltrimethylammonium bromide
• B. Sodium dodecylbenzene sulphonate
• C. Dodecylbenzene sulphonic acid
• D. Dodecylbenzene

Answer 1

The Correct Option is A

Cationic detergents are those that carry a positive charge in their molecular structure. They typically have a positively charged group, such as an ammonium ion (N⁺).

• Option A: Cetyltrimethylammonium bromide — This compound contains a quaternary ammonium group \(N^{+}\) which is characteristic of cationic detergents. Thus, this is a cationic detergent.
• Option B: Sodium dodecylbenzene sulphonate — This compound is an anionic detergent because it contains a sulfonate group \({SO}_3^{-}\)
• Option C: Dodecylbenzene sulphonic acid — This is also an anionic detergent, as it has a sulfonic acid group.
• Option D: Dodecylbenzene — This is a neutral compound and not a detergent.

Thus, the correct answer is (A): Cetyltrimethylammonium bromide, as it is a cationic detergent.

Answer 2

Cetyltrimethylammonium bromide is a cationic detergent. Cationic detergents have a positively charged hydrophilic head and are typically used as fabric softeners and disinfectants.

• Sodium dodecylbenzene sulfonate is an anionic detergent.
• Dodecylbenzene sulfonic acid is also an anionic detergent.
• Dodecylbenzene is a hydrocarbon that forms part of an anionic detergent structure but by itself is not a detergent.