Detergent
A detergent is a surfactant or a mixture of surfactants with "cleaning properties in dilute solutions."[1] In common usage, "detergent" refers to alkylbenzenesulfonates, a family of compounds that are similar to soap but are more soluble in hard water, because the polar sulfonate (of detergents) is less likely than the polar carboxyl (of soap) to bind to calcium and other ions found in hard water. In most household contexts, the term detergent by itself refers specifically to laundry detergent or dish detergent, as opposed to hand soap or other types of cleaning agents. Detergents are commonly available as powders or concentrated solutions. Detergents--like soaps-- work because they are amphiphilic - partly hydrophilic (polar) and partly hydrophobic (non-polar). Their dual nature facilitates the mixture of hydrophobic compounds (like oil and grease) with water. Because air is not hydrophillic, detergents are also foaming agents to varying degrees.
Chemical classification of detergents
Detergents are classified into three broad groupings, depending on the electrical charge of the surfactants.
Anionic detergents
Typical anionic detergents are alkylbenzenesulfonates. The alkylbenzene portion of these anions is lipophilic and the sulfonate is hydrophilic. Two varieties have been popularized, 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.[2] An estimated 6 billion kilograms of anionic detergents are produced annually for domestic markets.
Bile acids, such as deoxycholic acid (DOC), are anionic detergents produced by the liver to aid in digestion and absorption of fats and oils.
Cationic detergents
Cationic detergents are similar to the anionic ones, with a hydrophobic component, but, instead of the anionic sulfonate group, the cationic surfactants have quaternary ammonium as the polar end. The ammonium center is positively charged.[2]
Non-ionic and zwitterionic detergents
Non-ionic detergents are characterized by their uncharged, hydrophilic headgroups. Typical non-ionic detergents are based on polyoxyethylene or a glycoside. Common examples of the former include Tween, Triton, and the Brij series. These materials are also known as ethoxylates or PEGylates). Glycosides have a sugar as their uncharged hydrophilic headgroup. Examples include octyl-thioglucoside and maltosides. HEGA and MEGA series detergents are similar, possessing a sugar alcohol as headgroup.
Zwitterionic detergents possess a net zero charge arising from the presence of equal numbers of +1 and -1 charged chemical groups. Examples include CHAPS.
See surfactants for more applications.
Major applications of detergents
Laundry detergents
One of the largest applications of detergents is for cleaning clothing. The formulations are complex, reflecting the diverse demands of the application and the highly competitive consumer market. In general, laundry detergents contain water softeners, surfactants, bleach, enzymes, brighteners, fragrances, and many other agents. The formulation is strongly affected by the temperature of the cleaning water and varies from country to country.
Fuel additives
Both carburetors and fuel injector components of Otto engines benefit from detergents in the fuels to prevent fouling. Concentrations are about 300 ppm. Typical detergents are long-chain amines and amides such as polyisobuteneamine and polyisobuteneamide/succinimide.[3]
Biological Reagent
Reagent grade detergents are employed for the isolation and purification of intergral membrane proteins found in biological cells. Advancements in the purity and sophistication of detergents have facilitated structural and biophysical characterization of important membrane proteins such as ion channels[4], transporters, signaling receptors, and photosystem II. [5]
Soapless soap
Soapless soap refers to a soapfree liquid cleanser with a slightly acidic pH.[6] Soapless soaps are used in an array of products.
See also
References
- ^ http://goldbook.iupac.org/D01643.html
- ^ a b Eduard Smulders, Wolfgang Rybinski, Eric Sung, Wilfried Rähse, Josef Steber, Frederike Wiebel, Anette Nordskog, "Laundry Detergents" in Ullmann’s Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a08_315.pub2
- ^ Werner Dabelstein, Arno Reglitzky, Andrea Schütze, Klaus Reders "Automotive Fuels" in Ullmann’s Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheimdoi:10.1002/14356007.a16_719.pub2
- ^ Doyle DA, Morais Cabral J, Pfuetzner RA, Kuo A, Gulbis JM, Cohen SL, Chait BT, MacKinnon R (1998). "The structure of the potassium channel: molecular basis of K+conduction and selectivity". Science 280(5360): 69–77
- ^ Yasufumi Umena, Keisuke Kawakami, Jian-Ren Shen & Nobuo Kamiya. Crystal structure of oxygen-evolving photosystem II at a resolution of 1.9 A. Nature 2011; 473: 55-60. doi:10.1038/nature09913
- ^ Tyebkhan G (2002), "Skin cleansing in neonates and infants-basics of cleansers", Indian J Pediatr, 69 (9): 767–9, doi:10.1007/BF02723687, PMID 12420908.
External links
- About.com: How Do Detergents Clean
- Detergents and Surfactants
- Campbell tips for detergents chemistry, surfactants, and history related to laundry washing, destaining methods and soil.