Organosulfate

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Generic structure of an organosulfate, where R is an organyl group Organosulfate.svg
Generic structure of an organosulfate, where R is an organyl group

In organosulfur chemistry, organosulfates are a class of organic compounds sharing a common functional group with the structure R−O−SO−3. The SO4 core is a sulfate group and the R group is any organic residue. All organosulfates are formally esters derived from alcohols and sulfuric acid (H2SO4) although many are not prepared in this way. Many sulfate esters are used in detergents, and some are useful reagents. Alkyl sulfates consist of a hydrophobic hydrocarbon chain, a polar sulfate group (containing an anion) and either a cation or amine to neutralize the sulfate group. Examples include: sodium lauryl sulfate (also known as sulfuric acid mono dodecyl ester sodium salt) and related potassium and ammonium salts.

Contents

Applications

Alkyl sulfates are commonly used as an anionic surfactant in liquid soaps and detergents used to clean wool, as surface cleaners, and as active ingredients in laundry detergents, shampoos and conditioners. They can also be found in household products such as toothpaste, antacids, cosmetics and foods. Generally they are found in consumer products at concentrations ranging from 3-20%. In 2003 approximately 118,000 t/a of alkyl sulfates were used in the US [1]

Synthetic organosulfates

A common example is sodium lauryl sulfate, with the formula CH3(CH2)11OSO3Na. Also common in consumer products are the sulfate esters of ethoxylated fatty alcohols such as those derived from lauryl alcohol. An example is sodium laureth sulfate, an ingredient in some cosmetics. [2]

Alkylsulfate can be produced from alcohols, which in turn are obtained by hydrogenation of animal or vegetable oils and fats or using the Ziegler process or through oxo synthesis. If produced from oleochemical feedstock or the Ziegler process, the hydrocarbon chain of the alcohol will be linear. If derived using the oxo process, a low level of branching will appear usually with a methyl or ethyl group at the C-2 position, containing even and odd amounts of alkyl chains. [3] These alcohols react with chlorosulfuric acid:

ClSO3H + RCH2OH → RCH2OSO3H + HCl

Alternatively, alcohols can be converted to the half sulfate esters using sulfur trioxide: [4]

SO3 + RCH2OH → RCH2OSO3H

Laboratory routes

Specialized organosulfates can be prepared by the Elbs persulfate oxidation of phenols and the Boyland–Sims oxidation of anilines.

Dialkylsulfates

Structure of a diorganosulfate. SulfateEster.png
Structure of a diorganosulfate.

A less common family of organosulfates have the formula RO-SO2-OR'. They are prepared from sulfuric acid and the alcohol. The main examples are diethyl sulfate and dimethyl sulfate, colourless liquids that are used as reagents in organic synthesis. These compounds are potentially dangerous alkylating agents. Dialkylsulfates do not occur in nature. [5]

Natural sulfate esters

Heparin is a medication and naturally occurring organosulfate. Heparin General Structure V.1.svg
Heparin is a medication and naturally occurring organosulfate.

Several classes of sulfate esters exist in nature. Especially common are sugar derivatives such as keratan sulfate, chondroitin sulfate, and the anticoagulant heparin. [6] Post-translational modifications of some proteins entail sulfation, often at the phenol group of tyrosine residues. [7] A steroidal sulfate is estradiol sulfate, a latent precursor to the hormone estrogen.

A major portion of soil sulfur is in the form of sulfate esters. [8]

Metabolism

Sulfate is an inert anion, so nature activates it by the formation of ester derivative of adenosine 5'-phosphosulfate (APS) and 3'-phosphoadenosine-5'-phosphosulfate (PAPS). Many organisms utilize these reactions for metabolic purposes or for the biosynthesis of sulfur compounds required for life. [9] The formation and hydrolysis of natural sulfate esters are catalyzed by sulfatases (aka sulfohydrolases). [5]

Safety

Because they are widely used in commercial products, the safety aspects of organosulfates are heavily investigated. [10]

Human Health

Alkyl sulfates if ingested are well-absorbed and are metabolized into a C3, C4 or C5 sulfate and an additional metabolite. The highest irritant of the alkyl sulfates is sodium laurylsulfate, with the threshold before irritation at a concentration of 20%. Surfactants in consumer products are typically mixed, reducing likelihood of irritation. According to OECD TG 406, alkyl sulfates in animal studies were not found to be skin sensitizers. [10] [11]

Laboratory studies have not found alkyl sulfates to be genotoxic, mutagenic or carcinogenic. No long-term reproductive effects have been found. [12]

Environment

The primary disposal of alkyl sulfate from used commercial products is wastewater. The concentration of alkylsulfates in effluent from waste water treatment plants (WWTP) has been measured at 10 micrograms per litre (5.8×10−9 oz/cu in) and lower. Alkyl sulfates biodegrade easily, even starting likely before reaching the WWTP. Once at the treatment plant, they are rapidly removed by biodegradation. Invertebrates were found to be the most-sensitive trophic group to alkyl sulfates. Sodium laurylsulfate tested on Uronema parduczi, a protozoan, was found to have the lowest effect value with the 20 h-EC5 being 0.75 milligrams per litre (2.7×10−8 lb/cu in). Chronic exposure tests with C12 to C18 with the invertebrate Ceriodaphnia dubia found the highest toxicity is with C14 (NOEC was 0.045 mg/L).

In terms of thermal stability, alkyl sulfates degrade well before reaching their boiling point due to low vapor pressure (for C8-18 from 10-11 to 10-15 hPa). Soil sorption is proportional to carbon chain length, with a length of 14 and more having the highest sorption rate. Soil concentrations have been found to vary from 0.0035 to 0.21 milligrams per kilogram (5.6×10−8 to 3.4×10−6 oz/lb) dw.

Related Research Articles

Sodium laureth sulfate (SLES), an accepted contraction of sodium lauryl ether sulfate (SLES), also called sodium alkylethersulfate, is an anionic detergent and surfactant found in many personal care products and for industrial uses. SLES is an inexpensive and very effective foaming agent. SLES, sodium lauryl sulfate (SLS), ammonium lauryl sulfate (ALS), and sodium pareth sulfate are surfactants that are used in many cosmetic products for their cleaning and emulsifying properties. It is derived from palm kernel oil or coconut oil. In herbicides, it is used as a surfactant to improve absorption of the herbicidal chemicals and reduces time the product takes to be rainfast, when enough of the herbicidal agent will be absorbed.

Sodium dodecyl sulfate (SDS) or sodium lauryl sulfate (SLS), sometimes written sodium laurilsulfate, is an organic compound with the formula CH3(CH2)11OSO3Na and structure H3C−(CH2)11−O−S(=O)2−O−Na+. It is an anionic surfactant used in many cleaning and hygiene products. This compound is the sodium salt of the 12-carbon organosulfate. Its hydrocarbon tail combined with a polar "headgroup" give the compound amphiphilic properties that make it useful as a detergent. SDS is also component of mixtures produced from inexpensive coconut and palm oils. SDS is a common component of many domestic cleaning, personal hygiene and cosmetic, pharmaceutical, and food products, as well as of industrial and commercial cleaning and product formulations.

<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.

<span class="mw-page-title-main">Alkylation</span> Transfer of an alkyl group from one molecule to another

Alkylation is a chemical reaction that entails transfer of an alkyl group. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene. Alkylating agents are reagents for effecting alkylation. Alkyl groups can also be removed in a process known as dealkylation. Alkylating agents are often classified according to their nucleophilic or electrophilic character. In oil refining contexts, alkylation refers to a particular alkylation of isobutane with olefins. For upgrading of petroleum, alkylation produces a premium blending stock for gasoline. In medicine, alkylation of DNA is used in chemotherapy to damage the DNA of cancer cells. Alkylation is accomplished with the class of drugs called alkylating antineoplastic agents.

Ammonium lauryl sulfate (ALS) is the common name for ammonium dodecyl sulfate (CH3(CH2)10CH2OSO3NH4). The anion consists of a nonpolar hydrocarbon chain and a polar sulfate end group. The combination of nonpolar and polar groups confers surfactant properties to the anion: it facilitates dissolution of both polar and non-polar materials. This salt is classified as a sulfate ester. It is made from coconut or palm kernel oil for use primarily in shampoos and body-wash as a foaming agent. Lauryl sulfates are very high-foam surfactants that disrupt the surface tension of water in part by forming micelles at the surface-air interface.

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.

<span class="mw-page-title-main">Sulfonic acid</span> Organic compounds with the structure R−S(=O)2−OH

In organic chemistry, sulfonic acid refers to a member of the class of organosulfur compounds with the general formula R−S(=O)2−OH, where R is an organic alkyl or aryl group and the S(=O)2(OH) group a sulfonyl hydroxide. As a substituent, it is known as a sulfo group. A sulfonic acid can be thought of as sulfuric acid with one hydroxyl group replaced by an organic substituent. The parent compound is the parent sulfonic acid, HS(=O)2(OH), a tautomer of sulfurous acid, S(=O)(OH)2. Salts or esters of sulfonic acids are called sulfonates.

Fatty alcohols (or long-chain alcohols) are usually high-molecular-weight, straight-chain primary alcohols, but can also range from as few as 4–6 carbons to as many as 22–26, derived from natural fats and oils. The precise chain length varies with the source. Some commercially important fatty alcohols are lauryl, stearyl, and oleyl alcohols. They are colourless oily liquids (for smaller carbon numbers) or waxy solids, although impure samples may appear yellow. Fatty alcohols usually have an even number of carbon atoms and a single alcohol group (–OH) attached to the terminal carbon. Some are unsaturated and some are branched. They are widely used in industry. As with fatty acids, they are often referred to generically by the number of carbon atoms in the molecule, such as "a C12 alcohol", that is an alcohol having 12 carbons, for example dodecanol.

Dodecanol, or lauryl alcohol, is an organic compound produced industrially from palm kernel oil or coconut oil. It is a fatty alcohol. Sulfate esters of lauryl alcohol, especially sodium lauryl sulfate, are very widely used as surfactants. Sodium lauryl sulfate and the related dodecanol derivatives ammonium lauryl sulfate and sodium laureth sulfate are all used in shampoos. Dodecanol is tasteless, colorless, and has a floral odor.

<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.

Sodium myreth sulfate is a mixture of organic compounds with both detergent and surfactant properties. It is found in many personal care products such as soaps, shampoos, and toothpaste. It is an inexpensive and effective foaming agent. Typical of many detergents, sodium myreth sulfate consists of several closely related compounds. Sometimes the number of ethylene glycol ether units (n) is specified in the name as myreth-n sulfate, for example myreth-2 sulfate.

Sulfation is the chemical reaction that entails the addition of SO3 group. In principle, many sulfations would involve reactions of sulfur trioxide (SO3). In practice, most sulfations are effected less directly. Regardless of the mechanism, the installation of a sulfate-like group on a substrate leads to substantial changes.

<span class="mw-page-title-main">Sodium tetradecyl sulfate</span> Anionic surfactant in common use

Sodium tetradecyl sulfate (STS) is a common anionic surfactant. The compound consists of the sodium salt of the micelle-forming sulfate ester of tetradecanol. It is a white, water-soluble solid of low toxicity with many practical uses.

<span class="mw-page-title-main">Pyrosulfate</span>

In chemistry, disulfate or pyrosulfate is the anion with the molecular formula S
2O2−
7. Disulfate is the IUPAC name. It has a dichromate-like structure and can be visualised as two corner-sharing SO4 tetrahedra, with a bridging oxygen atom. In this anion, sulfur has an oxidation state of +6. Disulfate is the conjugate base of the hydrogen disulfate (hydrogen pyrosulfate) ion HS
2O−
7, which in turn is the conjugate base of disulfuric acid (pyrosulfuric acid).

<span class="mw-page-title-main">Alkylbenzene</span> Family of organic compounds

An alkylbenzene is a chemical compound that contains a monocyclic aromatic ring attaching to one or more saturated hydrocarbon chains. Alkylbenzenes are derivatives of benzene, in which one or more hydrogen atoms are replaced by alkyl groups. The simplest member, toluene, has the hydrogen atom of the benzene ring replaced by a methyl group. The chemical formula of alkylbenzenes is CnH2n-6.

<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 sulfosuccinate esters</span>

Sodium sulfosuccinate esters are organic compounds with the formula NaO3SCH(CO2R')CH2CO2R where R and R' can be H or alkyl groups. They comprise a large class of surfactants and emulsifiers used in cosmetics, pharmaceuticals, and cleaning agents. They are colorless salts. These materials can be further classified into monoesters (R' = H, R = alkyl) and diesters (R and R' = alkyl).

α-Olefin sulfonate Class of chemical compounds

α-Olefin sulfonates are a group of anionic surfactants, which are used as detergents. The compounds contain a - mostly linear, primary - alkyl R and a monovalent cation M, preferably sodium. The most frequently used example of this group of substances is sodium α-olefin sulfonate.

References

  1. ↑ CEH (October 2004). "Surfactants, household detergents and their raw materials". CEH Marketing Research Report.
  2. ↑ Eduard Smulders, Wolfgang von Rybinski, Eric Sung, Wilfried Rähse, Josef Steber, Frederike Wiebel, Anette Nordskog "Laundry Detergents" in Ullmann's Encyclopedia of Industrial Chemistry 2007, Wiley-VCH, Weinheim. doi : 10.1002/14356007.a08_315.pub2.
  3. ↑ Klaus Noweck, Wolfgang Grafahrend, "Fatty Alcohols" in Ullmann’s Encyclopedia of Industrial Chemistry 2006, Wiley-VCH, Weinheim. doi : 10.1002/14356007.a10_277.pub2
  4. ↑ Holmberg, Krister (2019). "Surfactants". Ullmann's Encyclopedia of Industrial Chemistry. pp. 1–56. doi:10.1002/14356007.a25_747.pub2. ISBN   978-3-527-30673-2.
  5. 1 2 Cleland, W. Wallace; Hengge, Alvan C. (2006). "Enzymatic Mechanisms of Phosphate and Sulfate Transfer". Chemical Reviews. 106 (8): 3252–3278. doi:10.1021/cr050287o. PMID   16895327.
  6. ↑ J. W. Fitzgerald (1976). "Sulfate ester formation and hydrolysis: a potentially important yet often ignored aspect of the sulfur cycle of aerobic soils". Bacteriological Reviews. 40 (3): 698–721. doi:10.1128/br.40.3.698-721.1976. PMC   413977 . PMID   791238.
  7. ↑ Moore, Kevin L. (2003). "The Biology and Enzymology of Protein Tyrosine O-Sulfation". Journal of Biological Chemistry. 278 (27): 24243–24246. doi: 10.1074/jbc.R300008200 . PMID   12730193.
  8. ↑ Scherer, H.W. (2001). "Sulphur in crop production — invited paper". European Journal of Agronomy. 14 (2): 81–111. doi:10.1016/S1161-0301(00)00082-4.
  9. ↑ M. T. Madigan, J. M. Martinko, J. Parker "Brock Biology of Microorganisms" Prentice Hall, 1997. ISBN   0-13-520875-0.
  10. 1 2 SDA/Alkylsulfate Consortium (2007). "SIDS Initial Assessment Profile. SIAM 25: Alkyl Sulfates, Alkane Sulfonates, and α-Olefin sulfonates" (PDF). OECD SIDS. Helsinki. Archived from the original (PDF) on 2016-03-03. Retrieved 2011-10-14.
  11. ↑ DE/ICCA (2009). "SIDS Initial Assessment Profile SIAM 25: Alkyl Sulfates, Alkane Sulfonates, and α-Olefin sulfonates". OECD.
  12. ↑ Wibbertmann, A; Mangelsdorf, I.; Gamon, K.; Sedlak, R. (2011). "Toxicological properties and risk assessment of the anionic surfactants category: Alkyl sulfates, primary alkane sulfonates, and α-Olefin sulfonate". Ecotoxicology and Environmental Safety. 74 (5): 1089–1106. doi:10.1016/j.ecoenv.2011.02.007. PMID   21463896.
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