A detergent is a
surfactant or a
mixture of surfactants with cleansing properties when in
dilute solutions.
There are a large variety of detergents, a common family being the
alkylbenzene sulfonates, which are
soap
Soap is a salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, soaps are us ...
-like compounds that are more soluble in
hard water, because the polar
sulfonate (of detergents) is less likely than the polar
carboxylate (of soap) to bind to calcium and other ions found in hard water.
Definitions
The word ''detergent'' is derived from the Latin adjective ''detergens'', from the verb ''detergere'', meaning to wipe or polish off. Detergent is a
surfactant or a
mixture of surfactants with cleansing properties when in
dilute solutions.
However, conventionally, detergent is used to mean synthetic cleaning compounds as opposed to ''soap'' (a salt of the natural
fatty acid
In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, f ...
), even though soap is also a detergent in the true sense. In domestic contexts, the term ''detergent'' refers to household cleaning products such as ''
laundry detergent'' or ''
dish detergent'', which are in fact complex mixture of different compounds, not all of which are by themselves detergents.
Detergency is the ability to remove unwanted substances termed 'soils' from a substrate (e.g clothing).
Structure and properties
Detergents are a group of compounds with an amphiphilic structure, where each molecule has a hydrophilic (polar) head and a long hydrophobic (non-polar) tail. The hydrophobic portion of these molecules may be straight- or branched-chain
hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...
s, or it may have a
steroid
A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter membrane fluidity; and ...
structure. The hydrophilic portion is more varied, they may be ionic or non-ionic, and can range from a simple or a relatively elaborate structure.
Detergents are surfactants since they can decrease the surface tension of water. Their dual nature facilitates the mixture of hydrophobic compounds (like oil and grease) with water. Because air is not hydrophilic, detergents are also
foaming agents to varying degrees.
Detergent molecules aggregate to form
micelle
A micelle () or micella () (plural micelles or micellae, respectively) is an aggregate (or supramolecular assembly) of surfactant amphipathic lipid molecules dispersed in a liquid, forming a colloidal suspension (also known as associated coll ...
s, which makes them soluble in water. The hydrophobic group of the detergent is the main driving force of micelle formation, its aggregation forms the hydrophobic core of the micelles. The micelle can remove grease, protein or soiling particles. The concentration at which micelles start to form is the critical micelle concentration (CMC), and the temperature at which the micelles further aggregate to separate the solution into two phases is the cloud point when the solution becomes cloudy and detergency is optimal.
Detergents work better in an alkaline pH. The properties of detergents are dependent on the molecular structure of the
monomer
In chemistry, a monomer ( ; '' mono-'', "one" + '' -mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization.
Classification
...
. The ability to foam may be determined by the head group, for example anionic surfactants are high-foaming, while nonionic surfactants may be non-foaming or low-foaming.
Chemical classifications of detergents
Detergents are classified into four broad groupings, depending on the electrical charge of the surfactants.
Anionic detergents
Typical anionic detergents are
alkylbenzene sulfonates. The
alkylbenzene
The alkylbenzenes are derivatives of benzene, in which one or more hydrogen atoms are replaced by alkyl groups of different sizes. They are a subset of the aromatic hydrocarbons. The simplest member is toluene, in which a hydrogen atom of the benze ...
portion of these
anions
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by con ...
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.
[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. ]
Anionic detergents is the most common form of detergents, and an estimated 6 billion kilograms of anionic detergents are produced annually for the 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 anionic ones, but
quaternary ammonium replaces the hydrophilic anionic sulfonate group. The ammonium sulfate center is positively charged.
[ Cationic surfactants generally have poor detergency.
]
Non-ionic detergents
Non-ionic detergents are characterized by their uncharged, hydrophilic headgroups. Typical non-ionic detergents are based on polyoxyethylene or a glycoside
In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. ...
. Common examples of the former include Tween, Triton
Triton commonly refers to:
* Triton (mythology), a Greek god
* Triton (moon), a satellite of Neptune
Triton may also refer to:
Biology
* Triton cockatoo, a parrot
* Triton (gastropod), a group of sea snails
* ''Triton'', a synonym of ''Triturus'' ...
, and the Brij series. These materials are also known as ethoxylates or PEGylates and their metabolites, nonylphenol. 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.
Amphoteric detergents
Amphoteric or zwitterionic detergents have zwitterions within a particular pH range, and possess a net zero charge arising from the presence of equal numbers of +1 and −1 charged chemical groups. Examples include CHAPS.
History
Soap is known to be have been used as a surfactant for washing clothes since the Sumerian time in 2,500 B.C. In ancient Egypt, soda was used as a wash additive. In the 19th century, synthetic surfactants began to be created, for example from olive oil. Sodium silicate
Sodium silicate is a generic name for chemical compounds with the formula or ·, such as sodium metasilicate , sodium orthosilicate , and sodium pyrosilicate . The anions are often polymeric. These compounds are generally colorless transparent ...
(water glass) was used in soap-making in the United States in the 1860s, and in 1876, Henkel
AG & Co. KGaA, commonly known as Henkel, is a German multinational chemical and consumer goods company headquartered in Düsseldorf, Germany. It is active in both the consumer and industrial sectors. Founded in 1876, the DAX company is organ ...
sold a sodium silicate-based product that can be used with soap and marketed as a "universal detergent" (''Universalwaschmittel'') in Germany. Soda was then mixed with sodium silicate to produce Germany's first brand name detergent Bleichsoda. In 1907 Henkel also added a bleaching agent sodium perborate to launch the first 'self-acting' laundry detergent Persil
Persil is a German brand of laundry detergent manufactured and marketed by Henkel around the world except in the United Kingdom, Ireland, France, Latin America (except Mexico), China, Australia and New Zealand, where it is manufactured and ma ...
to eliminate the laborious rubbing of laundry by hand.
During the First World War
World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was List of wars and anthropogenic disasters by death toll, one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, ...
, there was a shortage of oils and fats needed to make soap. In order find alternatives for soap, synthetic detergents were made in Germany by chemists using raw material derived from coal tar. These early products, however, did not provide sufficient detergency. In 1928, effective detergent was made through the sulfation of fatty alcohol, but large-scale production was not feasible until low-cost fatty alcohols become available in the early 1930s. The synthetic detergent created was more effective and less likely to form scum than soap in hard water, and can also eliminate acid and alkaline reactions and decompose dirt. Commercial detergent products with fatty alcohol sulphates began to be sold, initially in 1932 in Germany by Henkel
AG & Co. KGaA, commonly known as Henkel, is a German multinational chemical and consumer goods company headquartered in Düsseldorf, Germany. It is active in both the consumer and industrial sectors. Founded in 1876, the DAX company is organ ...
. In the United States, detergents were sold in 1933 by Procter & Gamble
The Procter & Gamble Company (P&G) is an American multinational consumer goods corporation headquartered in Cincinnati, Ohio, founded in 1837 by William Procter and James Gamble. It specializes in a wide range of personal health/consumer he ...
( Dreft) primarily in areas with hard water. However, sales in the US grew slowly until the introduction of 'built' detergents with the addition of effective phosphate builder developed in the early 1940s. The builder improves the performance of the surfactants by softening the water through the chelation of calcium and magnesium ions, helping to maintain an alkaline pH, as well as dispersing and keeping the soiling particles in solution. The development of the petrochemical industry after the Second World War also yielded material for the production of a range of synthetic surfactants, and alkylbenzene sulfonates became the most important detergent surfactants used. By the 1950s, laundry detergents had become widespread, and largely replaced soap for cleaning clothes in developed countries.
Over the years, many types of detergents have been developed for a variety of purposes, for example, low-sudsing detergents for use in front-loading washing machines, heavy-duty detergents effective in removing grease and dirt, all-purpose detergents and specialty detergents. They become incorporated in various products outside of laundry use, for example in dishwasher detergents, shampoo, toothpaste, industrial cleaners, and in lubricants and fuels to reduce or prevent the formation of sludge or deposits. The formulation of detergent products may include bleach
Bleach is the generic name for any chemical product that is used industrially or domestically to remove color (whitening) from a fabric or fiber or to clean or to remove stains in a process called bleaching. It often refers specifically, to ...
, fragrances, dyes and other additives. The use of phosphates in detergent, however, led to concerns over nutrient pollution and demand for changes to the formulation of the detergents. Concerns were also raised over the use of surfactants such as branched alkylbenzene sulfonate (tetrapropylenebenzene sulfonate) that lingers in the environment, which led to their replacement by surfactants that are more biodegradable, such as linear alkylbenzene sulfonate. Developments over the years have included the use of enzymes, substitutes for phosphates such as zeolite A and NTA, TAED as bleach activator
Bleach activators are compounds that allow a lower washing temperature than would be required otherwise to achieve the full activity of bleaching agents in the wash liquor. Bleaching agents, usually peroxides, are usually sufficiently active only ...
, sugar-based surfactants which are biodegradable and milder to skin, and other green friendly products, as well as changes to the form of delivery such as tablets, gels and pods.
Major applications of detergents
Household cleaning
One of the largest applications of detergents is for household and shop cleaning including dish washing and washing laundry. These detergents are commonly available as powders or concentrated solutions, and the formulations of these detergents are often complex mixtures of a variety of chemicals aside from surfactants, reflecting the diverse demands of the application and the highly competitive consumer market. These detergents may contain the following components:
* surfactants
* foam regulators
* builders
* bleach
* bleach activators
* enzymes
* dyes
* fragrances
* other additives
Fuel additives
Both carburetors and fuel injector components of internal combustion engine
An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal co ...
s benefit from detergents in the fuels to prevent fouling
Fouling is the accumulation of unwanted material on solid surfaces. The fouling materials can consist of either living organisms (biofouling) or a non-living substance (inorganic or organic). Fouling is usually distinguished from other surf ...
. Concentrations are about 300 ppm. Typical detergents are long-chain amine
In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent ...
s and amide
In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula , where R, R', and R″ represent organic groups or hydrogen atoms. The amide group is called a peptide bond when it i ...
s such as polyisobuteneamine and polyisobuteneamide/ succinimide.
Biological reagent
Reagent grade detergents are employed for the isolation and purification of integral membrane proteins found in biological cells
The cell is the basic structural and functional unit of life forms. Every cell consists of a cytoplasm enclosed within a membrane, and contains many biomolecules such as proteins, DNA and RNA, as well as many small molecules of nutrients an ...
. Solubilization of cell membrane
The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment (t ...
bilayers requires a detergent that can enter the inner membrane monolayer. Advancements in the purity and sophistication of detergents have facilitated structural and biophysical characterization of important membrane proteins such as ion channels also the disrupt membrane by binding lipopolysaccharide
Lipopolysaccharides (LPS) are large molecules consisting of a lipid and a polysaccharide that are bacterial toxins. They are composed of an O- antigen, an outer core, and an inner core all joined by a covalent bond, and are found in the out ...
, transporters, signaling receptors, and photosystem II.
See also
* Cleavable detergent
* Dishwashing liquid
* Dispersant
A dispersant or a dispersing agent is a substance, typically a surfactant, that is added to a suspension of solid or liquid particles in a liquid (such as a colloid or emulsion) to improve the separation of the particles and to prevent their sett ...
* Green cleaning
* Hard-surface cleaner
* Laundry detergent
* List of cleaning products
This is a list of cleaning products and agents. Cleaning agents are substances (usually liquids, powders, sprays, or granules) used to remove dirt, including dust, stains, bad smells, and clutter on surfaces. Purposes of cleaning agents include hea ...
* Triton X-100
References
External links
About.com: How Do Detergents Clean
for detergents chemistry
an
related to laundry washing
an
Formulation of Detergent
{{Authority control
Cleaning products
Membrane-active molecules
Surfactants