CAS number: 1643-20-5
An amine oxide, also known as an amine N-oxide and N-oxide, is a chemical compound that contains the functional group R3N+−O−, an N−O coordinate covalent bond with three additional hydrogen and/or hydrocarbon side chains attached to N.
Sometimes Amine Oxide is written as R3N→O or, wrongly, as R3N=O.
In the strict sense, the term amine oxide applies only to oxides of tertiary amines.
Sometimes Amine Oxide is also used for the analogous derivatives of primary and secondary amines.
Examples of amine oxides include pyridine N-oxide, a water-soluble crystalline solid with melting point 62–67 °C, and N-methylmorpholine N-oxide, which is an oxidant.
Amine Oxides are an Amphoteric class of surfactants that are excellent detergents, foam boosters and foam stabilizers.
Amine Oxides are used in detergent formulations to provide grease emulsification and soil suspension.
As an amphoteric, Amine Oxides act as nonionic surfactant in neutral and alkaline pH formulations.
Uses of Amine Oxides
As we mentioned at the start of this lesson, the cleaning and cosmetic industries rely heavily on amine oxides.
Within these industries, amine oxides often play a role as a surfactant.
A surfactant serves to lower the surface tension of a liquid or liquids.
Amine Oxide is this property that the cleaning and cosmetic industries rely on for creating detergents.
In order to have a good detergent, two important qualities must be met:
1. The molecule needs to have a charged, or polar, 'head group'.
2. The molecule needs to have at least one long chain of non-polar carbon and hydrogen atoms.
Applications of Amine Oxide:
Amine oxides are surfactants commonly used in consumer products such as shampoos, conditioners, detergents, and hard surface cleaners.
Alkyl dimethyl amine oxide (chain lengths C10–C16) is the most commercially used amine oxide.
They are considered a high production volume class of compounds in more than one member country of the Organisation for Economic Co-operation and Development (OECD); with annual production over 26,000, 16,000 and 6,800 tonnes (28,700, 17,600 and 7,500 short tons) in the US, Europe, and Japan, respectively.
In North America, more than 95% of amine oxides are used in home cleaning products.
They serve as stabilizers, thickeners, emollients, emulsifiers, and conditioners with active concentrations in the range of 0.1–10%.
The remainder (< 5%) is used in personal care, institutional, commercial products and for unique patented uses such as photography.
Properties of Amine Oxide:
Amine oxides are used as protecting group for amines and as chemical intermediates.
Long-chain alkyl amine oxides are used as amphoteric surfactants and foam stabilizers.
Amine oxides are highly polar molecules and have a polarity close to that of quaternary ammonium salts.
Small amine oxides are very hydrophilic and have an excellent water solubility and a very poor solubility in most organic solvents.
Amine oxides are weak bases with a pKb of around 4.5 that form R3N+−OH, cationic hydroxylamines, upon protonation at a pH below their pKb.
Amine oxides, known as N-oxides of tertiary amines, are classified as aromatic or aliphatic, depending on whether the nitrogen is part of an aromatic ring system or not.
This structural difference accounts for the difference in chemical and physical properties between the two types.
The higher aliphatic amine oxides are commercially important because of their surfactant properties and are used extensively in detergents.
Amine oxides that have surface-acting properties can be further categorized as nonionic surfactants; however, because under acidic conditions they show cationic properties, they have also been called cationic surfactants.
Most amine oxides undergo thermal decomposition between 90 and 200°C.
Aromatic amine oxides, have some pharmaceutical importance, do not demonstrate surface-acting properties and are more resistant than aliphatic amine oxides to reduction.
Linear alpha-olefins are the source of the largest volume of aliphatic amine oxides.
Fatty alcohols and fatty acids are also used to produce amine oxides.
Amine oxides used in industry are prepared by oxidation of tertiary amines with hydrogen peroxide solution.
Amine oxides are used in the detergent, organic synthesis, textile, and pharmaceutical industries.
Aliphatic amine oxides range from practically nontoxic to slightly toxic.
Among the aromatics, 4-nitroquinoline N-oxide is a powerful carcinogen, producing malignant tumors on the skin of mice.
2-Methyl, 2-ethyl, and 6-chloro derivatives of 4-nitroquinoline oxide are also carcinogens.
Amine Oxide Abstract:
Amine oxides are amine-based surfactants, represent one of the smaller classes of surfactants as compared to alcohol ethoxylates and sulfonated and sulfated anionic surfactants.
However, the uniqueness of the hydrophile in such surfactants provides specific properties that are difficult, if not impossible, to replicate by the use of classic nonionic and anionic surfactants.
The aim of the present paper is to survey the most important developments and understandings of the chemistry of amine oxide production, Amine Oxide’s physico-chemical studies, applications and environmental properties.
Key words: amine oxide, amine-based surfactant, hydrophile, physico-chemical, environmental
Amine Oxide Synthesis:
Almost all amine oxides are prepared by the oxidation of either tertiary aliphatic amines or aromatic N-heterocycles.
Hydrogen peroxide is the most common reagent both industrially and in academia, however peracids are also important.
More specialised oxidising agents can see niche use, for instance Caro's acid or mCPBA.
Spontaneous or catalysed reactions using molecular oxygen are rare.
Certain other reactions will also produce amine oxides, such as the retro-Cope elimination, however they are rarely employed.
An amine oxide is a chemical compound that contains the functional group R3N+−O−, an N−O with three additional hydrogen and/or hydrocarbon side chains attached to N.
An amine oxides acts as a non-ionic surfactant in neutral and alkaline pH and cationic in acidic conditions, and is compatible with most other surfactants.
Why use Amine Oxide?
Amine Oxide can be applied to cleaning products, they perform as excellent detergents, as well as providing excellent foam boosting and foam stabilising properties.
Amine Oxides are often used to provide viscosity and strong cleaning powers (grease emulsification and soil suspension) and are extensively used with both sodium hypochlorite and hydrogen peroxide to produce bleach based products.
Amine Oxide is stable foam which can used in the formulation of high alkalinity cleaning compounds.
Amine Oxide is used in industrial cleaning, once the product is sprayed on to contaminated equipment the amine oxide allows for excellent adhesion to the surface, providing an extended dwell time as required.
Amine Oxides can also be applied in personal care products, (shampoos, bath care and showers gels), as the product provides excellent thickening, emollient and emulsifying properties.
Amine Oxide applications:
-Hair conditioners & shampoos
-All purpose cleaning agents
-Liquid Bleach products
-Foam stabilisers in rubber and polymer industries
-High or low foaming capabilities
Why Amine Oxide?
Amine Oxide is tightly honed manufacturing process involving ozonation, reverse osmosis and UV filtration ensures that Amine Oxides are microbiologically pure, free from bacteria and other contaminants.
Amine oxides exhibit synergistic effects when combined with anionic and other non-ionic surfactants.
For example, when Amine Oxide is used in combination with anionic sodium lauryl ether sulphate (SLES) it increases Amine Oxide’s detergency effect.
Amine Oxide has a low residual hydrogen peroxide, less than 800ppm, whilst the industry norm is 1500ppm.
The finished product has a crystal clear ‘water white’ appearance, ensuring no need for additional colorant in the finished formulation.
Structure of Amine Oxides
Now that we can recognize the general formula for an amine oxide, let's take Amine Oxide a step further and look at them from a structural standpoint.
As we already mentioned, any amine oxide has three 'R' groups and an oxygen bonded to a central nitrogen atom.
Notice the formal positive charge on the nitrogen atom and the formal negative charge on the oxygen atom.
Although we use the same R designation for each side chain, they don't all necessarily have to be the same group.
All of the R groups could be identical, two could be the same and one different, or all three could be different.
The nature of the side chains can vary across a wide variety of amine oxides.
Amine Oxide is this feature that chemists leverage to help tune the properties of an amine oxide to the exact specifications they need for a specific application.
Amine Oxide Usage
Amine Oxide is useful as a foam booster and detergent in the following formulations or applications:
-Dish washing detergents
-All-purpose cleaning agents
-Liquid bleach products (as the surfactant)
-Foam stabilizer for rubber and polymer industries
Amine Oxide Key Points
Readily biodegradable means that Amine Oxide will have a low environmental impact.
Amine Oxide is generally produces a rich stable foam.
Good compatibility profile means that Amine Oxide can be used in a wide variety of products
In the reaction of pyridine and α-picoline N-oxide with p-nitrobenzenesulfinyl chloride, the N–O bond of the intermediate salt appears to cleave homolytically, as in the case of N-oxide with p-nitrobenzenesulfenyl chloride, and the p-nitrosulfonyl radical which arises from the homolytic cleavage of the N–O bond is considered to be so stable that only the secondary reaction products from the sulfonyl radical, and no heteroring-substituted products, are obtained.
Amine Oxide is the same in the case of unsubstituted benzenesulfinyl chloride.
Compounds with the general structure R3NO, where the R groups may be alike or different, are named by adding the class name "oxide" as a separate word after the name of the amine R3N.
Cyclic analogues are named in the same way, the position of the oxygen atom being indicated, where needed, by the locant of the ring atom (arabic numbers are preferred over capital italic element symbols as locants).
Where needed, the group may be designated by a prefix derived from "azinoyl-".
Amine Oxide can be used for numerous applications such as an emulsifier, emulsion stabilizer, and anti-static agent.
In shampoo formulations, Amine Oxide is used as a foam booster and thickener, and can be used in conjunction with or instead of alkanolamides.
In neutral or alkaline solutions, Amine Oxide exhibits a nonionic character and is therefore compatible with anionics.
In acid solutions, Amine Oxide exhibits mild quaternary properties which enable Amine Oxide to impart substantivity on skin and hair.
Amine Oxide is recommended for use in body washes, hand soaps and shampoos.
Amine Oxide Metabolites
Amine oxides are common metabolites of medication and psychoactive drugs.
Examples include nicotine, Zolmitriptan, and morphine.
Amine oxides of anti-cancer drugs have been developed as prodrugs that are metabolized in the oxygen-deficient cancer tissue to the active drug.
Amines are organic compounds which contain and are often actually based on one or more atoms of nitrogen.
Structurally amines resemble ammonia in that the nitrogen can bond up to three hydrogens, but amines also have additional properties based on their carbon connectivity.
In an amine, one or more of the hydrogen atoms from ammonia are replaced by organic substituents like alkyl (alkane chain) and aryl (aromatic ring) groups.
Another type of organic molecule contains nitrogen without being, strictly speaking, an amine: carboxylic acid derivatives containing a trivalent (three-bond) ammonia in ground state are actually amides instead of amines.
Amides and amines have different structures and properties, so the distinction is actually very important.
Organic-nitrogen compounds containing metals are also called amides, so if you see a molecule that has a nitrogen and either a carbonyl group or a metal next to that nitrogen, then you know that molecule should be an amide instead of an amine.
Amines can be either primary, secondary or tertiary, depending on the number of carbon-containing groups that are attached to them.
If there is only one carbon-containing group (such as in the molecule CH3NH2) then that amine is considered primary.
Two carbon-containing groups makes an amine secondary, and three groups makes Amine Oxide tertiary.
Utilizing the lone electron pair of nitrogen, Amine Oxide is sometimes energetically favored to use the nitrogen as a nucleophile and thus bind a fourth carbon-containing group to the amine.
In this case, Amine Oxide could be called a quaternary ammonium ion.
An organic compound with multiple amine groups is called a diamine, triamine, tetraamine and so forth, based on the number of amine groups (also called amino groups) attached to the molecule.
The chemical formula for methylene diamine (also called diaminomethane), for example, would be as follows: H2N-CH2-NH2
Aromatic amines have the nitrogen atom directly connected to an aromatic ring structure.
Due to its electron withdrawing properties, the aromatic ring greatly decreases the basicity of the amine – and this effect can be either strengthened or offset depending on what substituents are on the ring and on the nitrogen.
The presence of the lone electron pair from the nitrogen has the opposite effect on the aromatic ring itself; because the nitrogen atom can “loan” electron density to the ring, the ring itself becomes much more reactive to other types of chemistry.
For primary amines, where the amine is not the principal characteristic group, the prefix “amino-” is used.
For example: 4-aminobenzoic acid where the carboxylic acid is the principal characteristic.
Otherwise, the suffix “-amine” is used with with either the parent hybride or the R group substituent name.
Example: ethanamine or ethylamine.
Alternatively, the suffix “-azane” can be appended to the R group substituent name: Example: propylazane.
For secondary, tertiary, and quarternary amines, the naming convention is a bit different, but the suffixes are the same.
For symmetrical amines, the “di” or “tri” prefix is used depending on whether there are 2 or 3 substituents.
For example, dipropylamine is a secondary amine, and triphenylamine is a tertiary amine.
For asymmetric amines, the parent chain gets the “-amine” suffix.
This name is then prefixed with “N-” (indicating the nitrogen bond) and the substituent group name, for each substituent, using alphabetic order for tertiary amides.
For example, N-ethyl-N-methyl-propylamine, not N-methyl-N-ethyl-propylamine.
Amine Oxide Physical properties
Amine Oxide as one might readily guess, the inclusion of a heteroatom such as nitrogen in otherwise exclusively carbon and hydrogen molecules has quite an effect on the properties of amines as compared to alkanes.
Amine Oxide General properties
Hydrogen bonding significantly influences the properties of primary and secondary amines as well as the protonated derivatives of all amines.
Thus the boiling point of amines is higher than those for the corresponding phosphines (compounds containing phosphorus), but generally lower than the corresponding alcohols.
Alcohols, or alkanols, resemble amines but feature an -OH group in place of NR2.
Since oxygen is more electronegative than nitrogen, RO-H is typically more acidic than the related R2N-H compound.
Methyl, dimethyl, trimethyl, and ethyl amines are gases under standard conditions.
Most common alkyl amines are liquids, and high molecular weight amines are, quite naturally, solids at standard temperatures.
Additionally, gaseous amines possess a characteristic ammonia smell, while liquid amines have a distinctive “fishy” smell.
Most aliphatic amines display some solubility in water, reflecting their ability to form hydrogen bonds.
Solubility decreases relatively proportionally with the increase in the number of carbon atoms in the molecule – especially when the carbon atom number is greater than six.
Aliphatic amines also display significant solubility in organic solvents, especially in polar organic solvents.
Primary amines react readily with ketone compounds (such as acetone), however, and most amines are incompatible with chloroform and also with carbon tetrachloride as solvent solutions.
Aromatic amines have their lone pair electrons conjugated (“shared”) into the benzene ring, so their tendency to engage in hydrogen bonding is somewhat diminished.
The boiling points of these molecules are therefore usually somewhat higher than other, smaller amines due to their typically larger size.
They also often have relatively diminished solubility in water, although they retain their solubility in other organic solvents.
Aromatically conjugated amines are often quite toxic and have the potential to be easily absorbed through the skin, so should always be treated as “hazardous”.
capric dimethyl amine oxide
1-decanamine, N,N-dimethyl-, N-oxide
decyl dimethyl amine oxide
N,N-dimethyl decyl amine N-oxide
Amine oxide, ethyl(dimethyl)- [ACD/Index Name]
Ethanamine, N,N-dimethyl-, N-oxide
Ethyl(dimethyl)amine oxide [ACD/IUPAC Name]
Ethyl(dimethyl)aminoxid [German] [ACD/IUPAC Name]
Oxyde d'éthyl(diméthyl)amine [French] [ACD/IUPAC Name]