Organic peroxide
Encyclopedia
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
s containing the peroxide
Peroxide
A peroxide is a compound containing an oxygen–oxygen single bond or the peroxide anion .The O−O group is called the peroxide group or peroxo group. In contrast to oxide ions, the oxygen atoms in the peroxide ion have an oxidation state of −1.The simplest stable peroxide is hydrogen peroxide...
functional group
Functional group
In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of...
(ROOR'). If the R' is hydrogen, the compound is called an organic hydroperoxide. Peresters have general structure RC(O)OOR. The O-O bond easily breaks and forms free radicals of the form RO·. Thus, organic peroxides are useful as initiators
Radical initiator
In chemistry, radical initiators are substances that can produce radical species under mild conditions and promote radical reactions . These substances generally possess weak bonds—bonds that have small bond dissociation energies. Radical initiators are utilized in industrial processes such...
for some types of polymerisation, such as the epoxy
Epoxy
Epoxy, also known as polyepoxide, is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives....
resin
Resin
Resin in the most specific use of the term is a hydrocarbon secretion of many plants, particularly coniferous trees. Resins are valued for their chemical properties and associated uses, such as the production of varnishes, adhesives, and food glazing agents; as an important source of raw materials...
s used in glass-reinforced plastic
Glass-reinforced plastic
Fiberglass , is a fiber reinforced polymer made of a plastic matrix reinforced by fine fibers of glass. It is also known as GFK ....
s. MEKP
Methyl ethyl ketone peroxide
Methyl ethyl ketone peroxide is an organic peroxide, a high explosive similar to acetone peroxide. MEKP is a colorless, oily liquid whereas acetone peroxide is a white powder at STP; MEKP is slightly less sensitive to shock and temperature, and more stable in storage.Dilute solutions of 30 to 60%...
and benzoyl peroxide
Benzoyl peroxide
Benzoyl peroxide is an organic compound in the peroxide family. It consists of two benzoyl groups bridged by a peroxide link. Its structural formula is [C6H5C]2O2. It is one of the most important organic peroxides in terms of applications and the scale of its production...
are commonly used for this purpose. However, the same property also means that organic peroxides can either intentionally or unintentionally initiate explosive polymerisation in materials with unsaturated chemical bond
Chemical bond
A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electromagnetic force attraction between opposite charges, either between electrons and nuclei, or as the result of a dipole attraction...
s, and this process has been used in explosives
Explosive material
An explosive material, also called an explosive, is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure...
. Organic peroxides, like their inorganic counterparts, are powerful bleaching agents.
Properties
The O-O bond distance in peroxides is about 1.45 A and the R-O-O angles (R = H, C) are about 110° (water-like). Characteristically, the C-O-O-R (R = H, C) dihedral angles are about 120°. The O-O bond is relatively weak, with a bond dissociation energyBond dissociation energy
In chemistry, bond-dissociation energy or D0, is one measure of the bond strength in a chemical bond. It is defined as the standard enthalpy change when a bond is cleaved by homolysis, with reactants and products of the homolysis reaction at 0 K...
of 45 - 50 kcal/mol, less than half the strengths of C-C, C-H, and C-O bonds.
The oxidizing tendency of peroxides is related to the electronegativity of the substituents. Electrophilic peroxides are stronger O-atom transfer agents. For hydroperoxides, the O-atom donor tendency correlates with the acidity of the O-H bond. Thus, the order of oxidizing power is CF3CO3H > CH3CO3H > H2O2.
In polymer chemistry
Organic peroxides find numerous applications, often involving similar chemistry. Thus, peroxides serve as accelerators, activatorActivator
Activator may mean:* Activator , a DNA-binding protein that regulates one or more genes by increasing the rate of transcription* Activator , a type of effector that increases the rate of enzyme mediated reactions...
s, cross-link
Cross-link
Cross-links are bonds that link one polymer chain to another. They can be covalent bonds or ionic bonds. "Polymer chains" can refer to synthetic polymers or natural polymers . When the term "cross-linking" is used in the synthetic polymer science field, it usually refers to the use of...
ing agents, curing
Curing (chemistry)
Curing is a term in polymer chemistry and process engineering that refers to the toughening or hardening of a polymer material by cross-linking of polymer chains, brought about by chemical additives, ultraviolet radiation, electron beam or heat...
and vulcanization
Vulcanization
Vulcanization or vulcanisation is a chemical process for converting rubber or related polymers into more durable materials via the addition of sulfur or other equivalent "curatives." These additives modify the polymer by forming crosslinks between individual polymer chains. Vulcanized material is...
agents, hardeners, polymerisation initiators
Radical initiator
In chemistry, radical initiators are substances that can produce radical species under mild conditions and promote radical reactions . These substances generally possess weak bonds—bonds that have small bond dissociation energies. Radical initiators are utilized in industrial processes such...
, and promoters. Drying oil
Drying oil
A drying oil is an oil that hardens to a tough, solid film after a period of exposure to air. The oil hardens through a chemical reaction in which the components crosslink by the action of oxygen . Drying oils are a key component of oil paint and some varnishes...
s, as found in many paints and varnishes function via the formation of hydroperoxides.
Methyl ethyl ketone peroxide
Methyl ethyl ketone peroxide
Methyl ethyl ketone peroxide is an organic peroxide, a high explosive similar to acetone peroxide. MEKP is a colorless, oily liquid whereas acetone peroxide is a white powder at STP; MEKP is slightly less sensitive to shock and temperature, and more stable in storage.Dilute solutions of 30 to 60%...
, benzoyl peroxide
Benzoyl peroxide
Benzoyl peroxide is an organic compound in the peroxide family. It consists of two benzoyl groups bridged by a peroxide link. Its structural formula is [C6H5C]2O2. It is one of the most important organic peroxides in terms of applications and the scale of its production...
and to a smaller degree acetone peroxide
Acetone peroxide
Acetone peroxide is an organic peroxide and a primary high explosive. It takes the form of a white crystalline powder with a distinctive bleach-like odor....
are used as initiators for radical polymerization
Radical polymerization
Free radical polymerization is a method of polymerization by which a polymer forms by the successive addition of free radical building blocks. Free radicals can be formed via a number of different mechanisms usually involving separate initiator molecules...
of some resin
Resin
Resin in the most specific use of the term is a hydrocarbon secretion of many plants, particularly coniferous trees. Resins are valued for their chemical properties and associated uses, such as the production of varnishes, adhesives, and food glazing agents; as an important source of raw materials...
s, e.g. polyester
Polyester
Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate...
and silicone
Silicone
Silicones are inert, synthetic compounds with a variety of forms and uses. Typically heat-resistant and rubber-like, they are used in sealants, adhesives, lubricants, medical applications , cookware, and insulation....
, often encountered when making fiberglass
Fiberglass
Glass fiber is a material consisting of numerous extremely fine fibers of glass.Glassmakers throughout history have experimented with glass fibers, but mass manufacture of glass fiber was only made possible with the invention of finer machine tooling...
.
Bleaching and disinfecting agents
Benzoyl peroxideBenzoyl peroxide
Benzoyl peroxide is an organic compound in the peroxide family. It consists of two benzoyl groups bridged by a peroxide link. Its structural formula is [C6H5C]2O2. It is one of the most important organic peroxides in terms of applications and the scale of its production...
and hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
are used as bleaching and "maturing" agents
Flour bleaching agent
Flour bleaching agent is a food additive added to flour in order to make it appear whiter and to oxidize the surfaces of the flour grains and help with developing of gluten.Usual bleaching agents are:...
for treating flour
Flour
Flour is a powder which is made by grinding cereal grains, other seeds or roots . It is the main ingredient of bread, which is a staple food for many cultures, making the availability of adequate supplies of flour a major economic and political issue at various times throughout history...
to make its grain release gluten
Gluten
Gluten is a protein composite found in foods processed from wheat and related grain species, including barley and rye...
easier; the alternative is letting the flour slowly oxidize by air, which is too slow for the industrialized era. Benzoyl peroxide
Benzoyl peroxide
Benzoyl peroxide is an organic compound in the peroxide family. It consists of two benzoyl groups bridged by a peroxide link. Its structural formula is [C6H5C]2O2. It is one of the most important organic peroxides in terms of applications and the scale of its production...
is an effective topical medication for treating most forms of acne
Acne vulgaris
Acne vulgaris is a common human skin disease, characterized by areas of skin with seborrhea , comedones , papules , pustules , Nodules and possibly scarring...
.
In the synthesis of organic compounds
Many organic compounds are prepared using peroxides, most famously epoxides from alkeneAlkene
In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...
s. Tert-butyl hydroperoxide
Tert-Butyl hydroperoxide
tert-Butyl hydroperoxide is an organic peroxide widely used in a variety of oxidation processes, for example Sharpless epoxidation...
(TBHP) is an organic-soluble oxidant employed in a variety of metal-catalyzed oxidations, such as the Halcon process (to give propylene oxide
Propylene oxide
Propylene oxide is an organic compound with the molecular formula CH3CHCH2O. This colourless volatile liquid is produced on a large scale industrially, its major application being its use for the production of polyether polyols for use in making polyurethane plastics...
) and the Sharpless epoxidation
Sharpless epoxidation
The Sharpless Epoxidation reaction is an enantioselective chemical reaction to prepare 2,3-epoxyalcohols from primary and secondary allylic alcohols....
.
Explosives
Acetone peroxideAcetone peroxide
Acetone peroxide is an organic peroxide and a primary high explosive. It takes the form of a white crystalline powder with a distinctive bleach-like odor....
is an ingredient in explosive for paramilitaries
Paramilitary
A paramilitary is a force whose function and organization are similar to those of a professional military, but which is not considered part of a state's formal armed forces....
because of its ease of manufacture, despite its instability. It is notorious for its susceptibility to heat, friction, and shock. Hexamethylene triperoxide diamine
Hexamethylene triperoxide diamine
Hexamethylene triperoxide diamine is ahigh explosive organic compound, first synthesised in 1885 by Legler. The theorised structure lent itself well to acting as an initiating, or primary explosive...
(HMTD) is another widely-known explosive organic peroxide.
By autoxidation
Most peroxides are generated by the addition of O2 to hydrocarbons. Compounds with allylicAllyl
An allyl group is a substituent with the structural formula H2C=CH-CH2R, where R is the connection to the rest of the molecule. It is made up of a methylene , attached to a vinyl group . The name is derived from the Latin word for garlic, Allium sativum. Theodor Wertheim isolated an allyl...
and benzylic
Benzyl
In organic chemistry, benzyl is the term used to describe the substituent or molecular fragment possessing the structure C6H5CH2-. Benzyl features a benzene ring attached to a CH2 group.-Nomenclature:...
C-H bonds are amenable to this method. Cumene hydroperoxide is an intermediate in the cumene process
Cumene process
The Cumene process is an industrial process for developing phenol and acetone from benzene and propylene. The term stems from cumene , the intermediate material during the process. It was invented by Heinrich Hock in 1944 and independently by R. Ūdris and P...
of industrial synthesis of phenol
Phenol
Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...
. Ethers are susceptible to this reaction, a typical example being the formation of diethyl ether peroxide
Diethyl ether peroxide
Diethyl ether peroxides are a class of organic peroxides that slowly form in diethyl ether upon storage under air, light, or in the presence of metal by autoxidation.- Diethyl ether hydroperoxide :...
. The photooxidation of diene
Diene
In organic chemistry a diene or diolefin is a hydrocarbon that contains two carbon double bonds.Conjugated dienes are functional groups, with a general formula of CnH2n-2. Dienes and alkynes are functional isomers...
s affords dialkyl peroxides.
Many organometallic compounds insert O2 into the M-C bond. Organolithium and Grignard reagents react with O2 to give hydroperoxides upon hydrolysis. Oxymercuration of alkene
Alkene
In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...
s followed by reaction with a hydroperoxide proceeds similarly.
From H2O2
Carboxylic acidCarboxylic acid
Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...
s react with hydrogen peroxide to give peroxy acid
Peroxy acid
A peroxy acid is an acid which contains an acidic -OOH group. The two main classes are those derived from conventional mineral acids, especially sulfuric acid, and the organic derivatives of carboxylic acids...
s.
Reactions
Some peroxide reactions are:- Organic reduction to alcoholAlcoholIn chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
s with lithium aluminium hydrideLithium aluminium hydrideLithium aluminium hydride, commonly abbreviated to LAH or known as LithAl, is an inorganic compound with the chemical formula LiAlH4. It was discovered by Finholt, Bond and Schlesinger in 1947. This compound is used as a reducing agent in organic synthesis, especially for the reduction of esters,...
or phosphite esterPhosphite esterA phosphite ester or organophosphite is a type of chemical compound with the general structure P3. Phosphite esters can be considered as esters of phosphorous acid, H3PO3. A simple phosphite ester is trimethylphosphite, P3...
s - Cleavage to ketones and alcohols in the base catalyzed Kornblum–DeLaMare rearrangementKornblum–DeLaMare rearrangementThe Kornblum–DeLaMare rearrangement is a rearrangement reaction in organic chemistry in which a primary or secondary organic peroxide is converted to the corresponding ketone and alcohol under base catalysis...
Safety
As they combine unstably bound oxygen together with hydrogen and carbon in the same molecule, organic peroxides ignite easily and burn rapidly and intensely. The same applies to organic materials contaminated with organic peroxides. Since peroxides can form spontaneously in some materials, some caution must be exercised with such "peroxide forming materials", such as the common ethers diethyl etherDiethyl ether
Diethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...
, tetrahydrofuran
Tetrahydrofuran
Tetrahydrofuran is a colorless, water-miscible organic liquid with low viscosity at standard temperature and pressure. This heterocyclic compound has the chemical formula 4O. As one of the most polar ethers with a wide liquid range, it is a useful solvent. Its main use, however, is as a precursor...
or ethylene glycol dimethyl ether
Dimethoxyethane
Dimethoxyethane, also known as glyme, monoglyme, dimethyl glycol, ethylene glycol dimethyl ether, dimethyl cellosolve, and DME, is a clear, colorless, aprotic, and liquid ether that is used as a solvent. Dimethoxyethane is miscible with water.Dimethoxyethane is often used as a higher boiling...
.
Acetone peroxide
Acetone peroxide
Acetone peroxide is an organic peroxide and a primary high explosive. It takes the form of a white crystalline powder with a distinctive bleach-like odor....
, a powerful explosive, is an unwanted and dangerous byproduct of several chemical reactions, ranging from synthesis of MDMA (where it is a by-product
By-product
A by-product is a secondary product derived from a manufacturing process or chemical reaction. It is not the primary product or service being produced.A by-product can be useful and marketable or it can be considered waste....
of isosafrole
Safrole
Safrole, also known as shikimol, is a phenylpropene. It is a colorless or slightly yellow oily liquid. It is typically extracted from the root-bark or the fruit of sassafras plants in the form of sassafras oil , or synthesized from other related methylenedioxy...
oxidation in acetone) to industrial production of phenol
Phenol
Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...
(where the second product of the cumene process
Cumene process
The Cumene process is an industrial process for developing phenol and acetone from benzene and propylene. The term stems from cumene , the intermediate material during the process. It was invented by Heinrich Hock in 1944 and independently by R. Ūdris and P...
, acetone
Acetone
Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...
, is partially oxidized to peroxide on the second reaction step).
Accidental preparation of organic peroxides can occur by mixing ketone solvents (most commonly acetone) with waste materials containing hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
or other oxidizers and leaving the mixture standing for several hours.
Organic peroxides tend to react, explosively, with metals.
Organic peroxides are sensitive to light and have to be stored in darkness. Some decompose at room temperature and release gaseous products; gas ejectors on the lids of the containers are required. Based on the Self Accelerating Decomposition Temperature
Self Accelerating Decomposition Temperature
The self accelerating decomposition temperature is the lowest temperature at which an organic peroxide in a typical vessel or shipping package will undergo a self-accelerating decomposition. This reaction can be violent, usually rupturing the vessel or container dispersing peroxide, liquid...
, some peroxides have to be stored refrigerated.
Disposal of peroxides
Small amounts of organic peroxides can be disposed of by careful burning of a substance diluted to under 10%, or hydrolysisHydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
. For hydrolysis, using a solution consisting of 80 parts water, 20 parts sodium hydroxide, and 0.3 parts surfactant
Surfactant
Surfactants are compounds that lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid...
to allow easier wetting of the crystals of the peroxide. The recommended amount of the solution is 10 times the weight of the peroxide. The peroxide has to be slowly poured into the solution, with constant stirring to avoid local overheating. The reaction is slightly exothermic
Exothermic
In thermodynamics, the term exothermic describes a process or reaction that releases energy from the system, usually in the form of heat, but also in the form of light , electricity , or sound...
, but additional cooling is not required. The reaction is slow, and requires stirring for some 12 to 24 hours; the peroxide can then be considered decomposed.
External links
- OSH Answers - organic peroxidesCarolina Biological: The Perils of Peroxides
- Peroxide disposal
- Organic Peroxide Producers Safety Division. Oct. 2011. The Society of the Plastics Industry. 24 Oct. 2011.