A detergent is a surfactant or a mixture of surfactants having "cleaning properties in dilute solutions." Soaps are surfactants and detergents. Most commonly, detergent refers to alkylbenzenesulfonates, which are similar to soap but are less affected by "hard water." In most household contexts, the term detergent by itself refers specifically to laundry detergent or dish detergent, vs hand soap or other types of cleaning agents. Most detergent is delivered in powdered form.
Chemical classification of detergents
Detergents are classified into three broad groupings, depending on the electrical charge of the surfactants.
Typical anionic detergents are alkylbenzenesulfonates. The alkylbenzene portion of these anions is highly lipophilic and the sulfonate is the hydrophilic component. Two varieties have been popularlized, those with branched alkyl groups and those with linear alkyl groups. The former were largely phased out in economically advanced societies because they are poorly biodegradable. An estimated 6 billion kilograms of anionic detergents are produced annually for domestic markets.
Cationic detergents are usually based on quaternary ammonium compounds. The ammonium center is the polar and the alkyl chain provides the necessary hydrophobic components.
Ethoxylates are compounds that terminate in (OCH2CH2)nOH group. These groups are not charged but they are highly hydrophilic owing to the presence of many oxygen centres.
Non-ionic (or zwitterionic) detergents
These are characterized by their (net) uncharged, hydrophilic headgroups. They are based on polyoxyethylene clycol (i.e. Tween, Triton and Brij series), CHAPS, glycosides (i.e. octyl-thioglucoside, maltosides), bile acids such as DOC, lipids (HEGAs), or phosphine oxides. See surfactants for more applications.
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