Detergent Definition in Chemistry

How to Define a Detergent

woman's midsection holding detergent bottle

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A detergent is a surfactant or mixture of surfactants that has cleaning properties in dilute solution with water. A detergent is similar to soap, but with a general structure R-SO4-, Na+, where R is a long-chain alkyl group. Like soaps, detergents are amphiphilic, meaning they have both hydrophobic and hydrophilic regions. Most detergents are akylbenzenefulfonates. Detergents tend to be more soluble in hard water than soap because the sulfonate of detergent doesn't bind calcium and other ions in hard water as easily as the carboxylate in soap does.

Key Takeaways: Detergent Definition

  • Detergents are a class of surfactants with cleaning properties when diluted in water.
  • Most detergents are akylbenzenesulfonates.
  • Detergents are classified according to the electrical charge they carry as anionic, cationic, or non-ionic.
  • While detergents are used for cleaning, they also find use as fuel additives and biological reagents.

History

Synthetic detergents were developed in Germany in World War I. An alkyl sulfate surfactant was formulated because the Allied Blockade of Germany in 1917 caused a shortage of soap-making ingredients. The word "detergent" comes from the Latin word "detergere," which means "to wipe away." Prior to the invention of detergent, washing soda or sodium carbonate was most often used for dishwashing and laundering clothing. In the United States, the first liquid dishwashing detergent was produced in the 1930s, while in Europe, the first detergent for this purpose (Teepol) was made in 1942. Laundry detergents came into use around the same time, although they were available in both solid and liquid forms. Both dishwashing and laundry detergent contain numerous other compounds, typically including enzymes, bleach, fragrances, dyes, fillers, and (for laundry detergent) optical brighteners. The additives are necessary because detergents have a difficult time removing dyes, pigments, resins, and denatured proteins. Reagent detergents for biology tend to be pure forms of the surfactants.

Types of Detergents

Detergents are classified according to their electrical charge:

  • Anionic detergents: Anionic detergents have a net negative electrical charge. The liver produces bile acids, which are anionic detergents the body uses to digest and absorb fats. Commercial anionic detergents are usually alkylbenezesulfonates. The alkylbenzene is lipophilic and hydrophobic, so it can interact with fats and oils. The sulfonate is hydrophilic, so it can wash away soiling in water. Both linear and branched alkyl groups may be used, but detergents made with linear alkyl groups are more likely to be biodegradable.
  • Cationic detergents: Cationic detergents have a net positive electrical charge. The chemical structures of cationic detergents are similar to those of anionic detergents, but the sulfonate group is replaced by quaternary ammonium.
  • Non-ionic detergents: Non-ionic detergents contain an uncharged hydrophilic group. Usually, these compounds are based on a glycoside (sugar alcohol) or polyoxyethylene. Examples of non-ionic detergents include Triton, Tween, Brij, octyl thioglucoside, and maltoside.
  • Zwitterionic detergents: Zwitterionic detergents have equal numbers of +1 and -1 charges, so their net charge is 0. An example is CHAPS, which is 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate.

Detergent Uses

The largest application of detergents is for cleaning. Dishwashing detergent and laundry detergent are the most common formulations. However, detergents are also used as fuel additives and biological reagents. Detergents prevent fouling of fuel injectors and carburetors. In biology, detergents are used to isolate integral membrane proteins of cells.

Sources

  • Koley, D. and A.J. Bard. "Triton X-100 concentration effects on membrane permeability of a single HeLa cell by scanning electrochemical microscopy (SECM)." Proceedings of the National Academy of Sciences of the United States of America. 107 (39): 16783–7. (2010). doi:10.1073/pnas.1011614107
  • IUPAC. Compendium of Chemical Terminology (2nd ed.) (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). Online version (2019-) created by S. J. Chalk. ISBN 0-9678550-9-8. doi:10.1351/goldbook
  • Lichtenberg, D.; Ahyayauch, H.; Goñi, F.M. "The mechanism of detergent solubilization of lipid bilayers." Biophysical Journal. 105 (2): 289–299. (2013). doi:10.1016/j.bpj.2013.06.007
  • Smulders, Eduard; Rybinski, Wolfgang; Sung, Eric; Rähse, et al. "Laundry Detergents" in Ullmann's Encyclopedia of Industrial Chemistry 2002. Wiley-VCH, Weinheim. doi:10.1002/14356007.a08_315.pub2
  • Whitten, David O. and Bessie Emrick Whitten. Handbook of American Business History: Extractives, Manufacturing, and Services. Greenwood Publishing Group. (January 1, 1997). ISBN 978-0-313-25199-3.