Taurates

Last updated
Generic structure of a taurate. R is an odd numbered alkyl group CnH2n+1 with n = 7 - 17 carbon atoms. N-Acyl-Taurid.svg
Generic structure of a taurate. R is an odd numbered alkyl group CnH2n+1 with n = 7 – 17 carbon atoms.

Taurates (or taurides) are a group of mild anionic surfactants. They are composed of a hydrophilic head group, consisting of N-methyltaurine (2-methylaminoethanesulfonic acid) and a lipophilic residue, consisting of a long-chain carboxylic acid (fatty acid), both linked via an amide bond. The fatty acids used could be lauric (C12), myristic (C14), palmitic (C16) or stearic acid (C18), but mainly mixtures of oleic acid (C18:1) and coconut fatty acid (C8 – C18) are used. Besides sodium, no other counterions play a relevant role (these could be e. g. ammonium or other alkali or alkaline earth metals).

Contents

History

The surfactant group of the taurates was developed by I.G. Farben in Germany (just like the isethionates) and produced under the trade name Igepon at the Hoechst plant. Taurates rapidly spread due to their lime resistance and their oil-removing effect in textile treatment, as detergent raw material and in cosmetics applications. They had a breakthrough in particular because they do not felt wool during washing (as opposed to soap). The production of taurates decreased after the outbreak of the World War II, since only poor quality fatty acids were available due to the fat management. [1]

Production

Taurates were first obtained by the Schotten-Baumann method which is the reaction of long-chain carboxylic acid chlorides with aqueous solutions of the sodium salt of N-methyltaurine. [2]

N-Acyl-Tauride nach Schotten-Baumann.svg

The formation of (at least) equimolar amounts of sodium chloride is problematic, as they worsen the properties of surfactant mixtures with such taurates. The high salt content also makes the resulting taurates hygroscopic and corrosive. Another disadvantage of the Schotten-Baumann method is the hazardousness of the raw materials (such as phosphorus trichloride) and the intermediates (the acyl chlorides) and the accumulation of large amounts of waste materials, such as phosphonic acids. This synthesis pathway for taurates is therefore complicated and expensive. An advantage of the Schotten-Baumann method, however, is the very low content of free fatty acids in the end product. Taurates are also accessible by direct amidation of N-methyltaurine or its sodium salt with the corresponding fatty acid for 10 hours at 220 °C under nitrogen. [3] [4]

N-Acyl-Tauride durch Direktamidierung.svg

The excess fatty acid (added for a favorable equilibrium) usually remain in the product, which can interfere with some applications. The decomposition of N-methyltaurine already begins At temperatures above 200 °C and the resulting taurates darken and develop an unpleasant smell. Therefore, more recent variants of the direct amidation aim at gentler process conditions using suitable catalysts, such as sodium borohydride, [5] boric acid or zinc oxide. [6]

Properties

At room temperature, taurates are usually pasty masses, which dissolve well in water and react then neutral to slightly alkaline (pH 7–8). Their toxicity is low (the LD50, rat, oral is 7800 mg·kg−1 for cocoyl tauride). [7] They are easily biodegradable, they are not prone to bioaccumulation, but they are harmful to aquatic organisms (like all surfactants). Due to their amide bond, taurates are stable in a much wider pH range (about 2–10) than the corresponding esters, as for example isethionates. They are very mild surfactants with good foaming ability and high foam stability, even in the presence of fats and oils. Taurates retain their good washing properties even in hard water or seawater. Taurates are suitable in concentrations of about 2% as co-surfactants because of their good compatibility with all nonionic and anionic surfactants.

Use

Taurates are used as mild, well-foaming surfactants in body cleansing and personal care products (shampoos, liquid soaps and cleansers, face lotions, skin creams, bubble baths, syndet soaps), textile processing (wetting agents and detergents, dye dispersants), in crop protection formulations and in other industrial applications.

Literature

Related Research Articles

<span class="mw-page-title-main">Amide</span> Organic compounds of the form RC(=O)NR′R″

In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula R−C(=O)−NR′R″, where R, R', and R″ represent any group, typically organyl groups or hydrogen atoms. The amide group is called a peptide bond when it is part of the main chain of a protein, and an isopeptide bond when it occurs in a side chain, as in asparagine and glutamine. It can be viewed as a derivative of a carboxylic acid with the hydroxyl group replaced by an amine group ; or, equivalently, an acyl (alkanoyl) group joined to an amine group.

<span class="mw-page-title-main">Carboxylic acid</span> Organic compound containing a –C(=O)OH group

In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group attached to an R-group. The general formula of a carboxylic acid is often written as R−COOH or R−CO2H, sometimes as R−C(O)OH with R referring to an organyl group, or hydrogen, or other groups. Carboxylic acids occur widely. Important examples include the amino acids and fatty acids. Deprotonation of a carboxylic acid gives a carboxylate anion.

<span class="mw-page-title-main">Detergent</span> Surfactants with cleansing properties

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-like compounds that are more soluble in hard water, because the polar sulfonate is less likely than the polar carboxylate to bind to calcium and other ions found in hard water.

<span class="mw-page-title-main">Surfactant</span> Substance that lowers the surface tension between a liquid and another material

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 c. 1950. As they consist of a water-repellent and a water-attracting part, they enable water and oil to mix; they can form foam and facilitate the detachment of dirt.

In organic chemistry, an acyl chloride is an organic compound with the functional group −C(=O)Cl. Their formula is usually written R−COCl, where R is a side chain. They are reactive derivatives of carboxylic acids. A specific example of an acyl chloride is acetyl chloride, CH3COCl. Acyl chlorides are the most important subset of acyl halides.

In organic chemistry, ethoxylation is a chemical reaction in which ethylene oxide adds to a substrate. It is the most widely practiced alkoxylation, which involves the addition of epoxides to substrates.

A fabric softener or fabric conditioner is a conditioner that is applied to laundry after it has been washed in a washing machine. A similar, more dilute preparation meant to be applied to dry fabric is known as a wrinkle releaser.

<span class="mw-page-title-main">Laundry detergent</span> Type of detergent used for cleaning laundry

Laundry detergent is a type of detergent used for cleaning dirty laundry (clothes). Laundry detergent is manufactured in powder and liquid form.

<span class="mw-page-title-main">Isethionic acid</span> Chemical compound

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 1833. It is a white water-soluble solid used in the manufacture of certain surfactants and in the industrial production of taurine. It is most commonly available in the form of its sodium salt.

Nucleophilic acyl substitution (SNAcyl) describes a class of substitution reactions involving nucleophiles and acyl compounds. In this type of reaction, a nucleophile – such as an alcohol, amine, or enolate – displaces the leaving group of an acyl derivative – such as an acid halide, anhydride, or ester. The resulting product is a carbonyl-containing compound in which the nucleophile has taken the place of the leaving group present in the original acyl derivative. Because acyl derivatives react with a wide variety of nucleophiles, and because the product can depend on the particular type of acyl derivative and nucleophile involved, nucleophilic acyl substitution reactions can be used to synthesize a variety of different products.

<span class="mw-page-title-main">Ojima lactam</span> Chemical compound

The Ojima lactam is an organic compound of some importance in the commercial production of Taxol. This lactam was first synthesized by Iwao Ojima. The organic synthesis is an illustration of asymmetric synthesis via a chiral auxiliary.

<span class="mw-page-title-main">Cleaning agent</span> Substance used to remove dirt or other contaminants

Cleaning agents or hard-surface cleaners are substances used to remove dirt, including dust, stains, foul odors, and clutter on surfaces. Purposes of cleaning agents include health, beauty, removing offensive odor, and avoiding the spread of dirt and contaminants to oneself and others. Some cleaning agents can kill bacteria and clean at the same time. Others, called degreasers, contain organic solvents to help dissolve oils and fats.

Sodium lauroyl sarcosinate (INCI), also known as sarcosyl, is an anionic surfactant derived from sarcosine used as a foaming and cleansing agent in shampoo, shaving foam, toothpaste, and foam wash products.

<span class="mw-page-title-main">Alkylbenzene sulfonate</span> Class of chemical compounds

Alkylbenzene sulfonates are a class of anionic surfactants, consisting of a hydrophilic sulfonate head-group and a hydrophobic alkylbenzene tail-group. Along with sodium laureth sulfate, they are one of the oldest and most widely used synthetic detergents and may be found in numerous personal-care products and household-care products . They were introduced in the 1930s in the form of branched alkylbenzene sulfonates (BAS). However following environmental concerns these were replaced with linear alkylbenzene sulfonates (LAS) during the 1960s. Since then production has increased significantly from about one million tons in 1980, to around 3.5 million tons in 2016, making them most produced anionic surfactant after soaps.

<span class="mw-page-title-main">Sodium 2-hydroxyethyl sulfonate</span> Chemical compound

Sodium 2-hydroxyethyl sulfonate is the sodium salt of 2-hydroxyethane sulfonic acid, it is used as a hydrophilic head group in washing-active surfactants, known as isethionates (acyloxyethanesulfonates) due to its strong polarity and resistance to multivalent ions. It is being studied as a high production volume chemical in the "High Production Volume (HPV) Chemical Challenge Program" of the US Environmental Protection Ministry EPA.

Sodium salts are salts composed of a sodium cation and the conjugate base anion of some inorganic or organic acids. They can be formed by the neutralization of such acids with sodium hydroxide.

N-Oleoylsarcosine (Sarkosyl O) is an amphiphilic oleic acid derivative having a sarcosine head group (N-methylglycine) which is used as a water-in-oil emulsifier and corrosion inhibitor.

<i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>′-Tetramethylformamidinium chloride Chemical compound

N,N,N′,N′-Tetramethylformamidinium chloride is the simplest representative of quaternary formamidinium cations of the general formula [R2N−CH=NR2]+ with a chloride as a counterion in which all hydrogen atoms of the protonated formamidine [HC(=NH2)NH2]+ are replaced by methyl groups.

<i>N</i>-Methyltaurine Chemical compound

N-Methyltaurine is an aminosulfonic acid which is present as a zwitterion in the crystalline state and in polar solvents. In contrast to the widespread taurine, N-methyltaurine has been found in nature only in red algae, where it is formed by methylation of taurine. It is suitable for esterification with long-chain carboxylic acids to taurides (acylaminoethansulfonaten) because of its high polarity and the relatively good solubility of its alkaline earth metal salts, which are also used as mild anionic surfactants.

Isethionates are esters of long-chain aliphatic carboxylic acids (C8 – C18) with isethionic acid (2-hydroxyethanesulfonic acid) or salts thereof, such as ammonium isethionate or sodium isethionate. They are also referred to as acyl isethionates or acyloxyethanesulfonates.

References

  1. ↑ Stefan H. Lindner: Hoechst. Ein I.G. Farben Werk im Dritten Reich, München: C.H.Beck 2005, XVIII + 460 S., 29 Abb., 20 Tab., ISBN   978-3-406-52959-7.
  2. ↑ US 1932180,Guenther, Fritz; Münz, Ferdinand& Haussmann, Hans,"Sulphuric acid derivatives of amides",published 1933-10-24, assigned to I.G. Farbenindustrie AG
  3. ↑ US 2880219,Burnette, Llewellyn W.&Chiddix, Max E.,"Production of N-acyl taurides",published 1959-05-31, assigned to General Aniline & Film Corp.
  4. ↑ L.W. Burnette, M.E. Chiddix, Reaction of Fatty Acids with N-Methyl Taurine, J. Amer. Oil Chem. Soc., 39(11), 1962, 477–478, doi : 10.1007/BF02637229.
  5. ↑ US 5434276,Walele, Ismail I.&Syed, Samad A.,"Process for making N-acyl taurides",published 1995-07-18, assigned to Finetex, Inc.
  6. ↑ US 5496959,Day, James F.,"Preparation of N-acyl taurates",published 1996-03-05, assigned to Hoechst Celanese Corp.
  7. ↑ Sicherheitsdatenblatt für Geropon® TC 42 der Rhodia S.A.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.