Ethoxylate
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Ethoxylation is a
chemical reaction A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...
in which
ethylene oxide Ethylene oxide is an organic compound with the chemical formula, formula . It is a cyclic ether and the simplest epoxide: a three-membered Ring (chemistry), ring consisting of one oxygen atom and two carbon atoms. Ethylene oxide is a colorless a ...
adds to a substrate. It is the most widely practiced alkoxylation, which involves the addition of epoxides to substrates. In the usual application,
alcohol Alcohol most commonly refers to: * Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom * Alcohol (drug), an intoxicant found in alcoholic drinks Alcohol may also refer to: Chemicals * Ethanol, one of sev ...
s and
phenol Phenol (also called carbolic acid) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile. The molecule consists of a phenyl group () bonded to a hydroxy group (). Mildly acidic, it req ...
s are converted into R(OC2H4)nOH where n ranges from 1 to 10. Such compounds are called alcohol ethoxylates. Alcohol ethoxylates are often converted to related species called ethoxysulfates. Alcohol ethoxylates and ethoxysulfates are
surfactant Surfactants are chemical compounds that decrease the surface tension between two liquids, between a gas and a liquid, or interfacial tension between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming ...
s, used widely in cosmetic and other commercial products. The process is of great industrial significance with more than 2,000,000 metric tons of various ethoxylates produced worldwide in 1994.


Production

The process was developed at the
Ludwigshafen Ludwigshafen, officially Ludwigshafen am Rhein (; meaning " Ludwig's Port upon Rhine"), is a city in the German state of Rhineland-Palatinate, on the river Rhine, opposite Mannheim. With Mannheim, Heidelberg, and the surrounding region, it form ...
laboratories of
IG Farben Interessengemeinschaft Farbenindustrie AG (), commonly known as IG Farben (German for 'IG Dyestuffs'), was a German chemical and pharmaceutical conglomerate (company), conglomerate. Formed in 1925 from a merger of six chemical companies—BASF, ...
by Conrad Schöller and during the 1930s.


Alcohol ethoxylates

Industrial ethoxylation is primarily performed upon
fatty alcohol 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 ...
s in order to generate fatty alcohol ethoxylates (FAE's), which are a common form of
nonionic surfactant Surfactants are chemical compounds that decrease the surface tension between two liquids, between a gas and a liquid, or interfacial tension between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foami ...
(e.g.
octaethylene glycol monododecyl ether , Section2= {{Chembox Properties , Formula=C28H58O9 , MolarMass=538.75472 , Appearance= , Density= , MeltingPt= , BoilingPt= , Solubility= , CMC =8×10−5 M at 25 °C.{{cite journal , author1=Calum J. Drummond , author2=Gregory G. Warr , a ...
). Such alcohols may be obtained by the
hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a Catalysis, catalyst such as nickel, palladium or platinum. The process is commonly employed to redox, reduce or S ...
of
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, fr ...
s from
seed oils Vegetable oils are triglycerides extracted from plants. Some of these oils have been part of human culture for millennia. Edible vegetable oils are used in food, both in cooking and as supplements. Many oils, edible and otherwise, are burned ...
, or by
hydroformylation Hydroformylation, also known as oxo synthesis or oxo process, is an industrial process for the production of aldehydes from alkenes. This chemical reaction entails the net addition of a formyl group (CHO) and a hydrogen atom to a carbon-carbon d ...
in the
Shell higher olefin process The Shell higher olefin process (SHOP) is a chemical process for the production of linear alpha olefins via ethylene oligomerization and olefin metathesis invented and exploited by Royal Dutch Shell.''Industrial Organic Chemistry'', Klaus Weisserme ...
. The reaction proceeds by blowing ethylene oxide through the alcohol at 180 °C and under 1-2
bar Bar or BAR may refer to: Food and drink * Bar (establishment), selling alcoholic beverages * Candy bar * Chocolate bar Science and technology * Bar (river morphology), a deposit of sediment * Bar (tropical cyclone), a layer of cloud * Bar (u ...
of pressure, with
potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...
(KOH) serving as a
catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
. The process is highly exothermic ( ΔH -92 kJ/mol of ethylene oxide reacted) and requires careful control to avoid a potentially disastrous
thermal runaway Thermal runaway describes a process that is accelerated by increased temperature, in turn releasing energy that further increases temperature. Thermal runaway occurs in situations where an increase in temperature changes the conditions in a way t ...
. :ROH + n C2H4O → R(OC2H4)nOH The starting materials are usually
primary alcohols A primary alcohol is an alcohol in which the hydroxy group In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistr ...
as they tend to react 10–30× faster than do secondary alcohols. Typically 5-10 units of ethylene oxide are added to each alcohol, however ethoxylated alcohols can be more prone to ethoxylation than the starting alcohol, making the reaction difficult to control and leading to the formation of a product with varying
repeat unit In polymer chemistry, a repeat unit or repeating unit (or mer) is a part of a polymer whose repetition would produce the complete polymer chain (except for the end-groups) by linking the repeat units together successively along the chain, like the ...
length (the value of n in the equation above). Better control can be afforded by the use of more sophisticated catalysts, which can be used to generate
narrow-range ethoxylate Narrow-range ethoxylates (NREs) in chemistry are fatty alcohol polyglycol ethers with a narrow homolog distribution and are known nonionic surfactants. They can be produced industrially, for example, by the addition of ethylene oxide onto fatty ...
s. Ethoxylated alcohols are considered to be a high production volume (HPV) chemical by the US EPA.


Ethoxylation/propoxylation

Ethoxylation is sometimes combined with propoxylation, the analogous reaction using
propylene oxide Propylene oxide is an acutely toxic and carcinogenic organic compound with the molecular formula CH3CHCH2O. This colourless volatile liquid with an odour similar to ether, is produced on a large scale industrially. Its major application is its us ...
as the monomer. Both reactions are normally performed in the same reactor and may be run simultaneously to give a random polymer, or in alternation to obtain
block copolymer In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained from the copolymerization of two monomer species are some ...
s such as
poloxamer Poloxamers are nonionic triblock copolymers composed of a central hydrophobic chain of polyoxypropylene (poly(propylene oxide)) flanked by two hydrophilic chains of polyoxyethylene (poly(ethylene oxide)). The word was coined by BASF inventor, Ir ...
s. Propylene oxide is more hydrophobic than ethylene oxide and its inclusion at low levels can significantly affect the properties of the surfactant. In particular ethoxylated fatty alcohols which have been 'capped' with ~1 propylene oxide unit are extensively marketed as
defoamer A defoamer or an anti-foaming agent is a chemical additive that reduces and hinders the formation of foam in industrial process liquids. The terms anti-foam agent and defoamer are often used interchangeably. Strictly speaking, defoamers eliminate ...
s.


Ethoxysulfates

Ethoxylated fatty alcohols are often converted to the corresponding
organosulfate Organosulfates are a class of organic compounds sharing a common functional group with the structure R-O-SO3−. The SO4 core is a sulfate group and the R group is any organic residue. All organosulfates are formally esters derived from alcohols ...
s, which can be easily deprotonated to give
anionic surfactant Surfactants are chemical compounds that decrease the surface tension between two liquids, between a gas and a liquid, or interfacial tension between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming ...
s such as
sodium laureth sulfate 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 (soaps, shampoos, toothpaste, etc.) an ...
. Being salts, ethoxysulfates exhibit good water solubility (high HLB value). The conversion is achieved by treating ethoxylated alcohols with sulfur trioxide. Laboratory scale synthesis may be performed using
chlorosulfuric acid Chlorosulfuric acid (IUPAC name: sulfurochloridic acid) is the inorganic compound with the formula HSO3Cl. It is also known as chlorosulfonic acid, being the sulfonic acid of chlorine. It is a distillable, colorless liquid which is hygroscopic and ...
: :R(OC2H4)nOH + SO3 → R(OC2H4)nOSO3H :R(OC2H4)nOH + HSO3Cl → R(OC2H4)nOSO3H + HCl The resulting
sulfate ester Organosulfates are a class of organic compounds sharing a common functional group with the structure R-O-SO3−. The SO4 core is a sulfate group and the R group is any organic residue. All organosulfates are formally esters derived from alcohols ...
s are neutralized to give the salt: :R(OC2H4)nOSO3H + NaOH → R(OC2H4)nOSO3Na + H2O Small volumes are neutralized with alkanolamines such as triethanolamine (TEA). This 36 page report is an HERA document on this ingredient in European household cleaning products. In 2008, 381,000 metric tons of alcohol ethoxysulfates were consumed in North America.


Other materials

Although alcohols are by far the major substrate for ethoxylation, many nucleophiles are reactive toward ethylene oxide. Primary
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 substituen ...
s will react to give di-chain materials such as
polyethoxylated tallow amine Polyethoxylated tallow amine (also polyoxyethylene tallowamine, POE-tallowamine) refers to a range of non-ionic surfactants derived from animal fats (tallow). They are a class of polyethoxylated amines (POEAs). The abbreviation 'POEA' is often er ...
. The reaction of
ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...
produces important bulk chemicals such as
ethanolamine Ethanolamine (2-aminoethanol, monoethanolamine, ETA, or MEA) is an organic chemical compound with the formula or . The molecule is bifunctional, containing both a primary amine and a primary alcohol. Ethanolamine is a colorless, viscous liquid wit ...
,
diethanolamine Diethanolamine, often abbreviated as DEA or DEOA, is an organic compound with the formula HN(CH2CH2OH)2. Pure diethanolamine is a white solid at room temperature, but its tendencies to absorb water and to supercool meaning that it is often encou ...
, and triethanolamine.


Applications of ethoxylated products

Alcohol ethoxylates (AE) and alcohol ethoxysulfates (AES) are
surfactants Surfactants are chemical compounds that decrease the surface tension between two liquids, between a gas and a liquid, or interfacial tension between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsion#Emulsifiers , ...
found in products such as laundry detergents, surface cleaners, cosmetics, agricultural products, textiles, and paint.


Alcohol ethoxylates

As alcohol ethoxylate based surfactants are non-ionic they typically require longer ethoxylate chains than their sulfonated analogues in order to be water-soluble. Examples synthesized on an industrial scale include octyl phenol ethoxylate,
polysorbate 80 Polysorbate 80 is a nonionic surfactant and emulsifier often used in pharmaceuticals, foods, and cosmetics. This synthetic compound is a viscous, water-soluble yellow liquid. Chemistry Polysorbate 80 is derived from polyethoxylated sorbitan and ...
and
poloxamer Poloxamers are nonionic triblock copolymers composed of a central hydrophobic chain of polyoxypropylene (poly(propylene oxide)) flanked by two hydrophilic chains of polyoxyethylene (poly(ethylene oxide)). The word was coined by BASF inventor, Ir ...
s. Ethoxylation is commonly practiced, albeit on a much smaller scale, in the biotechnology and pharmaceutical industries to increase water solubility and, in the case of pharmaceuticals, circulatory half-life of non-polar organic compounds. In this application, ethoxylation is known as "
PEGylation PEGylation (or pegylation) is the process of both covalent and non-covalent attachment or amalgamation of polyethylene glycol (PEG, in pharmacy called macrogol) polymer chains to molecules and macrostructures, such as a drug, therapeutic protein ...
" (polyethylene oxide is synonymous with polyethylene glycol, abbreviated as PEG). Carbon chain length is 8-18 while the ethoxylated chain is usually 3 to 12 ethylene oxides long in home products. See preceding HERA reference for explanation of the publishing organisation. This 244 page book is the latest HERA document on ingredients of European household cleaning products. They feature both lipophilic tails, indicated by the alkyl group abbreviation, R, and relatively polar headgroups, represented by the formula (OC2H4)nOH.


Alcohol ethoxysulfates

AES found in consumer products generally are linear alcohols, which could be mixtures of entirely linear alkyl chains or of both linear and mono-branched alkyl chains. See preceding HERA reference for explanation of the publishing organisation. This 57 page report is the latest HERA document on this ingredient of European household cleaning products. Note, the HERA web site

access date as above, bears the December date; the document bears a date of January 2003.
A high-volume example of these is
sodium laureth sulfate 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 (soaps, shampoos, toothpaste, etc.) an ...
a
foaming agent A foaming agent is a material such as a surfactant or a blowing agent that facilitates the formation of foam. A surfactant, when present in small amounts, reduces surface tension of a liquid (reduces the work needed to create the foam) or increase ...
in
shampoo Shampoo () is a hair care product, typically in the form of a viscous liquid, that is used for cleaning hair. Less commonly, shampoo is available in solid bar format. Shampoo is used by applying it to wet hair, massaging the product into the ...
s and liquid soaps, as well as industrial
detergent 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 ...
s.


Environmental and safety


Alcohol ethoxylates (AEs)


Human health

Alcohol ethoxylates are not observed to be
mutagenic In genetics, a mutagen is a physical or chemical agent that permanently changes genetic material, usually DNA, in an organism and thus increases the frequency of mutations above the natural background level. As many mutations can cause cancer in ...
,
carcinogenic A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substan ...
, or
skin sensitizer Contact dermatitis is a type of acute or chronic inflammation of the skin caused by exposure to chemical or physical agents. Symptoms of contact dermatitis can include itchy or dry skin, a red rash, bumps, blisters, or swelling. These rashes are ...
s, nor cause reproductive or developmental effects. One byproduct of ethoxylation is
1,4-dioxane 1,4-Dioxane () is a heterocyclic organic compound, classified as an ether. It is a colorless liquid with a faint sweet odor similar to that of diethyl ether. The compound is often called simply dioxane because the other dioxane isomers ( 1,2- ...
, a possible human carcinogen. Undiluted AEs can cause dermal or eye irritation. In aqueous solution, the level of irritation is dependent on the concentration. AEs are considered to have low to moderate toxicity for acute oral exposure, low acute dermal toxicity, and have mild irritation potential for skin and eyes at concentrations found in consumer products.


Aquatic and environmental aspects

AEs are usually released down the drain, where they may be adsorbed into solids and biodegrade through anaerobic processes, with ~28–58% degraded in the sewer. The remaining AEs are treated at waste water treatment plants and biodegraded via aerobic processes with less than 0.8% of AEs released in effluent. If released into surface waters, sediment or soil, AEs will degrade through aerobic and anaerobic processes or be taken up by plants and animals. Toxicity to certain invertebrates has a range of
EC50 ] Half maximal effective concentration (EC50) is a measure of the concentration of a drug, antibody or toxicant which induces a Stimulus%E2%80%93response_model, response halfway between the baseline and maximum after a specified exposure time. Mo ...
values for linear AE from 0.1 mg/L to greater than 100 mg/L. For branched alcohol exthoxylates, toxicity ranges from 0.5 mg/L to 50 mg/L. The EC50 toxicity for algae from linear and branched AEs was 0.05 mg/L to 50 mg/L. Acute toxicity to fish ranges from
LC50 In toxicology, the median lethal dose, LD50 (abbreviation for " lethal dose, 50%"), LC50 (lethal concentration, 50%) or LCt50 is a toxic unit that measures the lethal dose of a toxin, radiation, or pathogen. The value of LD50 for a substance is ...
values for linear AE of 0.4 mg/L to 100 mg/L, and branched is 0.25 mg/L to 40 mg/L. For invertebrates, algae and fish the essentially linear and branched AEs are considered to not have greater toxicity than Linear AE.


Alcohol ethoxysulfates (AESs)


Biodegradation

The degradation of AES proceeds by ω- or
β-oxidation In biochemistry and metabolism, beta-oxidation is the catabolic process by which fatty acid molecules are broken down in the cytosol in prokaryotes and in the mitochondria in eukaryotes to generate acetyl-CoA, which enters the citric acid cycle, ...
of the alkyl chain, enzymatic hydrolysis of the sulfate ester, and by cleavage of an ether bond in the AES producing alcohol or alcohol ethoxylate and an ethylene glycol sulfate. Studies of aerobic processes also found AES to be readily biodegradable. The half-life of both AE and AES in surface water is estimated to be less than 12 hours. The removal of AES due to degradation via anaerobic processes is estimated to be between 75 and 87%.


In water

Flow-through laboratory tests in a terminal pool of AES with mollusks found the
NOEC Measures of pollutant concentration are used to determine risk assessment in public health. Industry is continually synthesizing new chemicals, the regulation of which requires evaluation of the potential danger for human health and the environm ...
of a snail, Goniobasis and the Asian clam, Corbicula to be greater than 730 ug/L. Corbicula growth was measured to be affected at a concentration of 75 ug/L. The mayfly, genus ''Tricorythodes'' has a normalized density NOEC value of 190 ug/L.


Human safety

AES has not been found to be genotoxic, mutagenic, or carcinogenic. A 2022 study revealed the expression of genes involved in cell survival, epithelial barrier, cytokine signaling, and metabolism were altered by rinse aid in concentrations used in professional dishwashers. The alcohol ethoxylates present in the rinse aid were identified as the culprit component causing the epithelial inflammation and barrier damage.{{cite journal , url=https://www.jacionline.org/article/S0091-6749(22)01477-4/fulltext , journal=
The Journal of Allergy and Clinical Immunology ''The Journal of Allergy and Clinical Immunology'' is a monthly peer-reviewed medical journal covering research on allergy and immunology. It is one of two official journals of the American Academy of Allergy, Asthma, and Immunology. The journal ...
, doi=10.1016/j.jaci.2022.10.020 , date=2022-12-01 , title=Gut epithelial barrier damage caused by dishwasher detergents and rinse aids , first1=Ismail , last1=Ogulur , first2=Yagiz , last2=Pat , first3=Tamer , last3=Aydin , first4=Duygu , last4=Yazici , first5=Beate , last5=Rückert , first6=Yaqi , last6=Peng , first7=Juno , last7=Kim , first8=Urszula , last8=Radzikowska , first9=Patrick , last9=Westermann


References

Addition reactions