Isethionates are

esters In chemistry, an ester is a chemical compound, compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds c ...

of long-chain aliphatic

carboxylic acids In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...

(C₈ – C₁₈) with

isethionic acid Isethionic acid is an organosulfur compound containing an alkylsulfonic acid located beta to a hydroxy group. Its discovery is generally attributed to Heinrich Gustav Magnus, who prepared it by the action of solid sulfur trioxide on ethanol in 18 ...

(2-hydroxyethanesulfonic acid) or salts thereof, such as ammonium isethionate or sodium isethionate. They are also referred to as acyl isethionates or acyloxyethanesulfonates. Like the

taurides Taurates (or taurides) are a group of mild anionic surfactants. They are composed of a hydrophilic head group, consisting of N-Methyltaurine, ''N''-methyltaurine (2-methylaminoethanesulfonic acid) and a lipophilic residue, consisting of a long-cha ...

, isethionates are a class of particularly mild anionic

surfactants Surfactants are chemical compounds that decrease the surface tension or interfacial tension between two liquids, a liquid and a gas, or a liquid and a solid. The word ''surfactant'' is a blend of "surface-active agent", coined in 1950. As t ...

which, unlike ordinary

soaps Soap is a surfactant cleaning compound used for personal or other cleaning. SOAP is a computer network protocol (originally an acronym for Simple Object Access Protocol), a protocol specification in computer networks. Soap or SOAP may also refer ...

, retain their washing-active properties even in hard water. Isethionates are obtained on an industrial scale reacting mixtures of carboxylic acids with salts of isethionic acid under acidic catalysis e. g. with

methanesulfonic acid Methanesulfonic acid (MsOH, MSA) or methanesulphonic acid (in British English) is an organosulfuric, colorless liquid with the molecular formula and structure . It is the simplest of the alkylsulfonic acids (). Salts and esters of methanesul ...

. The mixtures of carboxylic acids are obtained from the hydrolysis of animal fats (

tallow Tallow is a rendered form of beef or mutton suet, primarily made up of triglycerides. In industry, tallow is not strictly defined as beef or mutton suet. In this context, tallow is animal fat that conforms to certain technical criteria, inc ...

) or vegetable oils, preferably

coconut oil Coconut oil (or coconut fat) is an edible oil derived from the kernels, meat, and milk of the coconut palm fruit. Coconut oil is a white solid fat below around , and a clear thin liquid oil at higher temperatures. Unrefined varieties have a disti ...

, but also

palm oil Palm oil is an edible vegetable oil derived from the mesocarp (reddish pulp) of the fruit of oil palms. The oil is used in food manufacturing, in beauty products, and as biofuel. Palm oil accounted for about 36% of global oils produced from o ...

soybean oil Soybean oil (British English: soyabean oil) is a vegetable oil extracted from soybean (''Glycine max'') legumes. It is one of the most widely consumed cooking oils and the second most consumed vegetable oil. As a drying oil, processed soybean oil ...

castor oil Castor oil is a vegetable oil pressed from castor beans, the seeds of the plant ''Ricinus communis''. The seeds are 40 to 60 percent oil. It is a colourless or pale yellow liquid with a distinct taste and odor. Its boiling point is and its den ...

. :::::

Isethionates are solids which are often mixed with fatty acids (up to 30% by weight) to lower their freezing point. Despite its low water solubility (100ppm at 25 °C), the lower-priced sodium cocoylisethionate has found more widespread use than its well water-soluble ammonium salt (> 25 wt.% at 25 °C). To solubilize the sparsely soluble isethionates and taurides, the formation of mixtures with amphoteric surfactants (such as

cocamidopropyl betaine Cocamidopropyl betaine (CAPB) is a mixture of closely related organic compounds derived from coconut oil and dimethylaminopropylamine. CAPB is available as a viscous pale yellow solution and it is used as a surfactant in personal care products a ...

) are proposed. From such mixtures, it is possible to prepare liquid, clear and transparent aqueous concentrates which are liquid at room temperature. Isethionates are characterized by excellent skin compatibility, excellent foaming (even in hard water), good cleansing properties and a pleasant skin feel. They are non-toxic and readily biodegradable. However, in contrast to the

, they are not long-term stable outside a pH range of 5 to 8. Isethionates are used in solid soaps (so-called syndet bars) and in other personal care products such as lotions, washing and shower gels, shampoos, liquid soaps, shaving creams, and other cosmetic and dermatological preparations.

List

References

Literature

Wilfried Umbach (Hrsg.), ''Kosmetik und Hygiene von Kopf bis Fuß'', Wiley-VCH Verlag GmbH & Co. KGaA, 3. vollst. überarb. u. erw. Auflage (27. Juli 2012), {{ISBN, 978-3-527-30996-2 Sulfonic acids Carboxylate esters Surfactants