MCQ Detailed View

Detergents are cleansing agents that work by reducing surface tension and emulsifying oils, fats, and other impurities so they can be removed by water. The main active ingredients in commercial detergents are compounds that act as surfactants. These surfactants usually consist of a hydrophobic tail (long hydrocarbon chain) and a hydrophilic head (ionic or polar group), giving the molecule both water-repelling and water-attracting properties.

The most common surfactants in traditional detergents are sodium salts of fatty acids (RCOONa), where “R” represents a long hydrocarbon chain derived from natural fats and oils. These compounds are known as soaps. When dissolved in water, the soap molecules arrange themselves in micelles: the hydrophobic tails cluster around grease or oil, while the hydrophilic heads remain in contact with water. This structure allows oil and dirt particles to be lifted off surfaces and washed away.

Analyzing the options:

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  RCOON (sodium salts of fatty acids): This is the correct answer, as soaps and many detergent formulations are primarily based on this structure.

  
  


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  RONa (alkoxides): These are strong bases, not used as detergents.

  
  


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  RSNa (thiolates): These are sulfur-containing compounds with foul odors, not used in cleaning.

  
  


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  R–OSO₃Na (sodium alkyl sulfates): These are actually synthetic detergents found in some formulations, but the question emphasizes commercial detergents mainly contain, and the classical/primary answer is RCOONa.

  
  

In real industrial practice, modern detergents often combine RCOONa (soaps) with synthetic surfactants like R–OSO₃Na for better performance in hard water. However, the fundamental base of commercial cleaning agents is still the sodium salts of fatty acids.

Thus, the correct answer is RCOONa, as these compounds are the main cleaning agents present in commercial detergents.