Question 62 What are the three main classes of surfactants? What two types of ch
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Question 62
What are the three main classes of surfactants? What two types of chemical behavior are combined into every surfactant? How is it possible to construct so many different specific chemical molecules that can act as surfactants? Why do soap molecules tend to accumulate at the air/water surface? Exactly how does a surfactant work as a "dispersant" for oil or grease? This is a sodium laureth sulfate molecule. For providing polarity, It has the chemical features of two types of surfactant built in .. where and what are they?Explanation / Answer
60. In general, all surfactants have fairly similar structures. A surfactant consists of a polar hydrophilic end and a non-polar hydrophobic hydrocarbon chain. The hydrophilic end is attracted to water while the hydrocarbon chain is repelled by water. Therefore, in solutions, the hydrophilic end is exposed to the surface of the water while the hydrophobic chain is at the center of the surfactant.
Depending on the nature of the polar head, surfactants are classified into three major categories:
(i) Anionic Surfactants: Anionic surfactants are more common. The hydrophilic polar head group contains an anionic functional group like sulfate, sulfonate, phosphate ester, carboxylate ester, etc. These functional groups are attached to hydrocarbon chains as in ammonium lauryl sulfate, sodium stearate, etc.
(ii) Cationic Surfactants: These surfactants contain polar functional groups, most common of these being amines. These surfactants show pH dependent functions. Most primary and secondary amines are charged below pH < 10. Common examples are cetrimonium bromide, cetylpyridinium chloride, etc.
(iii) Non-Ionic Surfactants: These surfactants are polar, but the head group doesn’t dissociate into cation or anion; but remain undissociated in aqueous solutions. Common non-ionic groups are alcoholic or phenolic –OH groups. Common examples are polyethylene glycol, polypropylene glycol, etc.
61. The two types of chemical behavior that every surfactant exhibits is a combination of hydrophilic and hydrophobic behavior. The hydrophilic polar ends attract water while the hydrophobic ends are repelled by water, but they are attracted to organic groups.
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