Peroxides and peroxide-forming compounds

Peroxides and peroxide-forming compounds

By Donald E. Clark

Inorganic and organic peroxides,because of their exceptional reac-tivity and oxidative potential are

widely used in research laboratories.This review is intended to serve as aguide to the hazards and safety issuesassociated with the laboratory use,handling, and storage of inorganic andorganic peroxy-compounds and per-oxide-forming compounds.

The relatively weak oxygen-oxygenlinkage (bond-dissociation energy of20 to 50 kcal mole�1) is the character-istic structure of organic and inor-ganic peroxide molecules, and is thebasis for their reactivity and tendencyfor spontaneous decomposition. Theunusual weakness of the -O-O- bondis probably a consequence of the mo-lecular and electronic structure of per-oxide molecules and of the relativelyhigh electronegative character of theoxygen atoms. As a class, peroxidesare exceptionally prone to violent de-composition that can be initiated byheat, mechanical shock, or friction,especially in the presence of certaincatalysts and promoters.

The hazards of inorganic and or-ganic peroxides and peroxide-formingchemicals have been long recognizedso that most relevant information isnow found in text books on organicchemistry and laboratory safety. Acomprehensive three-volume serieson the chemistry of organic peroxidesincludes a chapter on safety issues as-sociated with these materials.1,2,3,4

Bretherick5 included a discussion oforganic peroxide5 in a chapter onhighly reactive and unstable com-pounds and used “oxygen balance” topredict the stability of individual com-pounds and to assess the hazard po-tential of an oxidative reaction. Jack-son et al.6 addressed the use ofperoxidizable chemicals in the re-search laboratory and published rec-ommendations for maximum storagetime for common peroxide-forminglaboratory solvents. Several solvents,(e.g., diethyl ether) commonly used inthe laboratory can form explosive re-action products through a relativelyslow oxidation process in the pres-ence of atmospheric oxygen. The riskof explosion can be greatly reduced byfollowing storage and handling prac-tices that are compatible with theproperties of these materials.1,6 Morerecently, Kelly7 reviewed the chemis-try and safe handling of peroxide-forming chemicals and included pro-cedures on detection and removal ofperoxides from laboratory solvents.Safety awareness, prudent handlingand proper storage are essential whenworking with these compounds.1,2

INORGANIC PEROXIDES ANDPEROXYACIDS

The O-O bond of hydrogen peroxideis covalent. In solution, persalts of al-kali metals (M2O2) are ionized to themonopositive alkali metal ion (M�),and the dinegative peroxide ion(O2

�2). Metallic peroxides are consid-ered to be salts of hydrogen peroxideand react with water to produceH2O2.1

Hydrogen peroxide alone is not ex-plosive and has a long shelf life if it ishandled properly and is not contami-

nated. However, concentrated hydro-gen peroxide (�30%), in contact withordinary combustible materials (e.g.,fabric, oil, wood, or some resins)poses significant fire or explosion haz-ards. Peroxides of alkali metals are notparticularly shock sensitive, but candecompose slowly in the presence ofmoisture and may react violently witha variety of substances, including wa-ter. Thus, the standard iodide test forperoxides must not be used with thesewater-reactive compounds.1

Inorganic peroxides are used as ox-idizing agents for digestion of organicsamples and in the synthesis of or-ganic peroxides. They react violentlywith reducing agents and with severalclasses of organic compounds to gen-erate organic peroxide and hydroper-oxide products.4 Dry Caro’s reagent(monopersulfuric acid — K2O2 � con.H2SO4) reacts readily with carbonylcompounds (in the synthesis of or-ganic peroxides) and can react explo-sively with aldehydes and alco-hols.3,4,5 Similar characteristics areassociated with other inorganic perox-ides and persalts. Peroxides may formon the surface of finely divided alkalimetals and their amides and readilyform superoxides, and ozonides suchas KO3.8

Inorganic per-compounds (e.g., so-dium peroxide, sodium perborate, andsodium persulfate) may react with in-organic cobalt and copper com-pounds, iron or iron compounds,metal oxide salts, and acids or basesresulting in rapid, uncontrolled de-composition reactions. Persulfates(e.g., peroxy sulfate) are highly reac-tive and may ignite when in contactwith metals.2,4,8

Perhalogen compounds (e.g., peroxychloride) are extremely shock sensitive

Donald E. Clark, Ph.D., FAIC, RBPis the Chemical and Biological SafetyOfficer at Texas at A&M University,College Station, TX, USA.

FEATURE

12 © Division of Chemical Health and Safety of the American Chemical Society 1074-9098/01/$20.00Published by Elsevier Science Inc. PII S1074-9098(01)00247-7

and should be avoided unless abso-lutely necessary. They can react withacids (especially organic acids) to pro-duce near-anhydrous perchloric acid.Perhalogen compounds of alkali metaland alkali earth elements are explosive,but are less sensitive than heavy metalperchlorates and organic perchlorates.Ammonium periodate is especially sen-sitive to friction. Perchlorates (e.g. mag-nesium perchlorate [Mg(ClO4)2] mar-keted as “Anhydrone”) should not beused as a drying agent if in contact withorganic compounds or with a strong de-hydrating acid (such as in a drying trainthat includes a sulfuric acid bubblecounter) is possible.9,10 Perchloratehazards are multiplied by increasedtemperature, dryness and/or perchlor-ate content. Abuse of any one or moreof these parameters accounts for nearlyall perchlorate related incidents.

Perhalogen acids (e.g., hot perchlo-ric acid) are widely used as potent ox-idizing agents. Cold 70% perchloricacid is a strong acid but is not a strongoxidizing agent. The oxidizing powerof perchloric acid increases with tem-perature and hot, concentrated solu-tions can be very dangerous. The max-imum concentration of perchloricacid commercially available is anaqueous solution of 70% HClO4.However, perchloric acid solutionscan become highly concentrated fromevaporation (e.g., spill or heated di-gestion procedure) and anhydrousperchloric acid is capable of sponta-neous explosion. Highly concentratedperchloric should be disposed ofwithin 10 days or if any discolorationdevelops. Anhydrous perchloric is ex-plosive in contact with wood, paper,carbon, and organic solvents. Diges-tion of organic material in boiling per-chloric acid must be conducted is achemical fume hood that is specifi-cally designed for that purpose. Per-chloric acid fume hoods include a spe-cial wash-down feature to preventbuildup of dangerous organic or me-tallic (copper and copper alloys) per-chlorates.9 Aqueous perchloric acidsolutions are not combustible.

Organic alcohols, aldehydes, ke-tones, ethers, and dialkyl sulfoxidescan react violently with concentratedperchloric acid, especially at elevatedtemperatures. Furr9 included a review

of the properties, hazards and use ofperchlorates, including perchloricacid in the CRC Handbook of Labo-ratory Safety. He stated that, “Themost detailed available account of thechemistry of perchloric acid and a ref-erence highly recommended to every-one who will be working with per-chlorates is given by J. S. Schumacherin the American Chemical SocietyMonograph Series 146, Perchlorates,Their Properties, Manufacture, andUses.” Procedures for dismantling anexhaust ventilation system suspectedof perchlorate contamination are in-cluded in the CRC Handbook.9 Pub-lication of an updated version ofSchilt’s Perchloric Acid and Per-chlorates is pending.11

Dilute hydrogen peroxide solutions(i.e., 3%) are contact irritants andhigher concentrations can cause se-vere chemical burns. Peroxide chemi-cal burns should be washed gently butthoroughly and may require medicalattention.5,10 The acute toxicity of per-chloric acid is moderate [oral LD50

(rat) 1100 mg/kg; oral LD50 (dog) 400mg/kg]. It is a potent irritant at lowconcentrations and is very corrosiveand can cause severe burns to skin,eyes and mucous membranes at higherconcentrations (especially when hot).Perchloric acid has not been found tobe carcinogenic or to cause reproduc-tive, or developmental toxicity inhumans.12

ORGANIC PEROXIDES AND OTHERPER-COMPOUNDSOrganic peroxides are characterizedby the bivalent -O-O- structure andare considered to be structural deriv-atives of hydrogen peroxide with oneor both of the hydrogen atoms re-placed by an organic moiety. Becauseof the weak peroxide bond, organicperoxides are predisposed to sponta-neous decomposition. They are excep-tionally labile to catalysts and promot-ers that accelerate decomposition.1

As a class, organic peroxides areamong the most hazardous substanceshandled in the lab. Most are highlyflammable and extremely sensitive toshock, heat, spark, friction, impact,and ultraviolet light. They readily re-act with strong oxidizing and reducing

agents. Each peroxide compound ischaracterized by a specific, condition-dependent rate of decomposition. Achange in critical parameters (e.g., in-creased temperature) can promoterapid increase in the decompositionrate, culminating in a violent explo-sion.1 The potential energy of organicperoxides is low compared to conven-tional explosives, but high enough tobe very hazardous.

The acute toxicity of organic perox-ides is relatively low (i.e., peraceticacid: oral LD50, rat; 1540 mg/kg; der-mal LD50, rabbit 1410 mg/kg). How-ever, most are highly irritating to skin,eyes, and mucous membranes andperacetic acid may be a weak carcin-ogen in mice. There are no data tosuggest that exposure to peracetic acidproduces carcinogenic, reproductiveor developmental toxicity in humans.Other organic peracids (e.g., perben-zoic acid and m-chloroperbenzoicacid) are less toxic, less volatile andless hazardous to handle than perace-tic acid.12 Exposure to peroxides andassociated materials, including vaporsand aerosols, should be minimized.Aliphatic peroxyacids have a sharp,unpleasant odor, the intensity ofwhich decreases with increasing mo-lecular weight.1,4 Liquid peroxidesmay penetrate rubber gloves upon ex-tended exposure.5

ORGANIC PEROXIDES: SYNTHESISAND USE

The synthesis of organic peroxides fre-quently begins with hydrogen perox-ide. Hydroperoxides can be preparedby reaction of alkyl halides, esters ofsulfuric or sulfonic acids, or alcoholswith hydrogen peroxide in alkaline so-lution. Peroxy groups may be intro-duced into susceptible organic mole-cules by treatment with a hydro-peroxide in the presence of a catalystsuch as cuprous chloride. Hydroper-oxides and acylperoxides are preparedfrom amyl halides or anhydrides, andfrom amides of the imidazolide type.Diacyl peroxides are synthesized bytreatment of carboxylic acids with hy-drogen peroxide in the presence of di-cyclohexylcarboiimide. Mixed alkyl-acylperoxides (peresters) can be made

13Chemical Health & Safety, September/October 2001

from acyl halides and hydroper-oxides.13

Organic peroxides are widely usedas a source of free radicals to initiate anumber of addition and polymeriza-tion reactions.1,13 The chain reactioncan be initiated by ultraviolet light, bythe presence of a radical source,and/or by the peroxide itself. Alkyl- oraryl hydroperoxides (R-O-O-H) anddialkyl peroxides (R-O-O-R1) are themost common types of organic perox-ides used in organic synthesis. Otherclasses of organic peroxides includeacylperoxides, polyperoxides, per-oxyesters, alkylidene peroxides, per-carboxylic acids, and cyclic peroxides.These compounds, because of their in-herent instability and propensity fordecomposition that increases withconcentration, are generally not soldin high purity. Reactivity and instabil-ity decrease with increasing molecularweight. Some of the most commonlow molecular weight peroxides in-clude tert-butyl peroxide, tert-butylhydroperoxide, peracetic acid, ben-zoyl peroxide, and isopropylbenzene(cumene) hydroperoxide).

Reagent purity can be extremely im-portant in reactions that intentionallyor unknowingly involve peroxides.The catalytic potential of organic per-oxides and the free radicals they gen-erate can change the course of aplanned reaction. For example, theaddition of hydrogen halides to simpleolefins, in the absence of peroxides,proceeds via an electrophilic mecha-nism, and the orientation is in accordwith the Markovnikov Rule.13 Whenperoxides are present, the reactionproceeds via a free-radical mecha-nism. The reorientation of the reac-tion is called the anti-Markovnikovaddition (Figure 1).13 The premise offree-radical mechanism is supportedby the fact that very low levels of per-oxide can alter the orientation of thereaction, and conversely, can be pre-vented by very small amounts of per-oxide-inhibitor.13 This can be criticalin a reaction mixture if autoxidation ofthe solvent has produced smallamounts of peroxide derivatives. Or-ganic peroxides are very sensitive tocontamination (especially heavy-metal compounds, metal oxide salts,alkaline materials including amines,

strong acids, and many varieties ofdust and dirt). The presence of thesematerials can initiate rapid, uncon-trolled decomposition of peroxidesand possible fire or explosion. Theconsequences of accidental contami-nation from returning withdrawn ma-terial to the storage container can bedisastrous. Once withdrawn, the per-oxide must never be returned to itsstorage container.1

Within a structural series of the per-oxy compounds, sensitivity and insta-bility increase as active oxygen con-tent and oxygen balance increase.Oxygen balance is the difference be-tween the oxygen content of a mole-cule or mixture, and that required forcomplete oxidation of oxidizable ele-ments (i.e., CO2, H2O, etc). If the ox-ygen is deficient, oxygen balance isnegative, and positive if in excess. Ox-ygen balance is expressed as a weightpercentage with the appropriate sign.5

The stability of a compound becomesincreasingly doubtful as the oxygencontent approaches that necessary tooxidize the other elements to theirlowest valance state. Peroxide sensi-tivity may also be related to its heat ofdecomposition, activation energy, andreaction kinetics.1,4,5

In a laboratory reaction system, it isimportant to maintain the oxygen bal-ance as low (negative) as possible inorder to control the rate of energy re-lease. This is aided by slow addition ofoxidant to the reaction mixture and bycontrolling reaction conditions. Ap-propriate mixing and temperaturecontrols are essential to prevent local-ization of the oxidant and develop-ment of “heat pockets,” conditionsthat can lead to an uncontrollablereaction.

Violent exothermic reactions mayresult when peracids contact ethers,metal chloride solutions, olefins, somealcohols and ketones, and carboxylicanhydrides, with peracids to produceshock-sensitive peroxide derivatives.“Run-away” peroxide decompositionmay result from contact betweenperacids and some metal ions (e.g.,iron, copper, cobalt, chromium, andmanganese).1,4,5 Hence, safety in deal-ing with organic peroxides dependson knowledgeable and prudent han-dling and storage.

The rate of peroxide-involved reac-tions increases exponentially with in-crease in temperature. Once initiated,the reaction temperature will continueto rise until thermal balance is estab-lished or until the material heats todecomposition. Destructive resultsoccur when the reaction releases en-ergy in a quantity or a rate too great tobe dissipated by the immediate envi-ronment of the reacting system.1,5,14

Any impediment to ready dissipationof heat flow will lead to dramaticallyincreased internal temperature.

In certain conditions, a chemical re-action can approach adiabatic condi-tions when a strong exothermic reac-tion is driven by an unusually wellinsulated heating system (e.g., flaskcompletely surrounded by a thick heat-ing mantle with a top jacket) or withunusually high heat capacity (e.g., deep-well oil bath). Under adiabatic condi-tions, spontaneously unstable materialswill self-heat to destruction. Thus, ap-propriate temperature control and heatdissipation is essential for avoiding theout-of-control acceleration of the exo-thermic reactions (normal, polymeriza-tion, or decomposition). The reactionrate and heat and/or gas released that

Figure 1. Effect of the presence of peroxide on chemical reaction products.

14 Chemical Health & Safety, September/October 2001

may go unnoticed during small-scaleexperiments may lead to an explosivesituation when conducted on a largerscale. It is especially important to in-clude fail-safe devices to protect againstevents such as utility failure into proce-dures that are unfamiliar or unat-tended.5

Because even gram-scale explosionscan be very serious, reactant quanti-ties should be limited to a practicalminimum. Stringent precautions anddown scaling (concentration, quan-tity, volume) are especially criticalwhen working with a new or unfamil-iar organic peroxides or procedure.Once ignited, the burning of peroxidescannot be controlled. The area shouldbe evacuated if any appreciable quan-tity of peroxide ignites.1,5

Reactant concentration is especiallycritical in reactions involving highlyreactive chemicals, including perox-ides. Peroxides should be addedslowly and cautiously to the reactionmedium. The addition should be com-pleted prior to heating and with goodagitation. Agitation should be friction-free and should never be provided bygases unless inert and free of oxygenor other reactive components (even intrace quantities).

The concentration of each reactanthas direct influence on reaction rateand therefore, the rate of heat release.Peroxide concentration should rarelybe as high as 1%, in a polymerization orother free-radical reaction. Unless thereare compelling reasons to do otherwise,peroxide concentration should not ex-ceed 10%, especially with vigorous re-actants. Very hazardous situations canresult from the intentional or accidentalincrease in reactant or catalyst concen-tration to an otherwise safe procedure.It is essential to conduct all such oper-ations in a properly functioning labora-tory chemical hood. All sources of acci-dental ignition must be excluded fromareas where peroxides are used.5,6

Preparation of concentrated stocksolutions of organic peroxide mono-mers may be extremely hazardous. Aviolent reaction can result from inad-vertent mixing of promoters (frequent-ly used with peroxides in polymeriza-tion systems) with full-strengthperoxide. The addition of peroxide to

the hot monomer is also extremelydangerous.1

Preplanning and attention to detailare essential when handling highly re-active materials. Manipulation ofequipment during the reaction shouldbe minimized. Appropriate protectivedevices (e.g., fume hood, barricadeshield) should be in place. Equipmentto provide full protection to eyes, face,hands, and body should be worn.Other potentially exposed personsshould be notified whenever a hazard-ous procedure is initiated.14 Specificsafety guidelines for laboratory use oforganic peroxides can be found in ref-erences 1 and 5.

STORAGE OF ORGANIC PEROXIDESAND PER-COMPOUNDSPublished data on the decompositionkinetics of organic peroxides at stor-age temperatures are sparse. However,the tendency of organic peroxides toundergo spontaneous decompositionand gassing is well recognized.1,9

Peroxides should be purchased inminimum practical quantities andstorage time in inventory should beminimized. The quantity within thework area should be limited to a one-day supply. Peroxides should bestored in isolation and separated fromthe work area and from other organicchemicals and combustible materials.Specific information on appropriatematerial and design criteria for perox-ide storage is available.14 The condi-tion of the containers should be con-firmed at regular intervals.

Containers must be vented and keptupright to avoid escape of liquidthrough the vent. In most cases, per-oxides should be stored in plastic con-tainers to maintain structural integrityand to minimize the potential for det-onation from shock or friction. In ad-dition, plastic containers are mechan-ically weak and don’t provide highconfinement thus reducing the extentof pressure buildup before the con-tainer ruptures. Peroxides must neverbe housed in a container with screwcap or ground glass closure becausedetonation can be initiated by frictiongenerated by opening a lid in contactwith the dry peroxide.1

Organic peroxides are especially un-

stable when dry, and should be storedonly under wet (water or non-reactivehydrocarbon) conditions. Most organicperoxides (especially lower MW com-pounds) are extremely unstable at ornear room temperature and must beprepared, shipped and stored under re-frigeration. Conversely, some crystallineperoxides can be stored for years atroom temperature with little evidenceof decomposition. There are also situa-tions in which cooling may cause in-creased impact sensitivity. This can oc-cur when the cooling of a liquidcomposition causes separation of liquidphases or precipitation of peroxide crys-tals. In either case, one of the separatedphases is very likely to be more impact-sensitive than the original solution. Forexample at 0° C, crystals of acetyl per-oxide (extremely impact-sensitive) canprecipitate from a 25% solution in di-methyl phthalate. Users of new or in-completely studied peroxy compounds(especially liquids and solutions)should be alert to the possibility of en-hanced hazards on cooling. Any evi-dence of layer separation or crystal for-mation is a very strong indicator ofincreased impact sensitivity.1

The consequences of storage at ele-vated temperature are highly scale-de-pendent. Container size is the primarydeterminant of the rate of decomposi-tion without self-acceleration. Unlessthe self-decomposition rate is knownto be low, the storage vessel of exper-imental peroxide compositions shouldbe as small as practical.1

The self-accelerating decompositiontest (SADT) addresses the scale-de-pendence phenomenon. The SADT(also called the “Temperature of NoReturn” or “Ignition Temperature”) isthe temperature at which a heat-sen-sitive compound can auto-ignite withrapid and violent decomposition. TheSADT is used internationally to esti-mate safe storage and transportationconditions for unstable chemicals.The SADT can be a very useful char-acteristic of peroxides and is often in-cluded in the MSDS.1,4,15

Liquid compositions tend to bemore susceptible to contaminationthan solids. However, the presence ofsmall quantities of liquid catalysts orpromoters can lead to intense localtemperature rise in solid peroxides.


Limited diffusion and lack of convec-tion may lead to an intense hot spotthat can initiate a violent, self-propa-gating reaction. Although dilution ofperoxide solutions decreases the po-tential for violent decomposition, therate of auto-decomposition often in-creases.1 Decomposition of stored re-agents can lead to loss of activity, aswell as self-heating and runaway reac-tions. Contaminated, partially decom-posed, outdated, or surplus organicperoxides should be disposed or de-stroyed under stringently controlledconditions.16

Stabilizers are usually not necessarywith solid or aqueous solutions of or-ganic peroxides. However, there are afew instances in which the rate of de-composition can be reduced by inclu-sion of materials that complex or ad-sorb heavy-metal ions in thecomposition. For example, additives(e.g. dipicolinic acid and sodium py-rophosphate) that function as “anti-catalysts” can greatly reduce the de-composition rate of aqueous peroxyacid solutions. This is analogous tothe stabilization of hydrogen peroxidesolutions. Materials that trap free rad-ical can reduce the reaction rate of adecomposition reaction that proceedsthrough a chain reaction mechanism.This may be of limited practical use ifthe chain scavenger also depletes thefree radicals necessary for thereaction.1

PEROXIDATION OF ORGANICSOLVENTS

Certain organic solvents slowly un-dergo autoxidation under very mildconditions (�100° C in the presenceof a free radical initiator), to form un-stable and dangerous products. Al-though ethers are generally recog-nized as peroxide formers, otherorganic structures are also capable ofspontaneous autoxidation to generatehighly unstable hydroperoxides, andmonomer- and polymeric peroxides.7

The reaction is catalyzed by light orsome impurity and occurs when com-pounds are allowed access to atmo-spheric oxygen. Under certain circum-stances oxygen attacks the C-H bondof certain hydrocarbons to form hy-

droperoxides (compounds containingthe -OOH group).

The hydroperoxides can react fur-ther to produce alcohols, ketones,peroxides, and more complex prod-ucts. These reactions are relatively un-predictable, so that the reaction haslimited use in synthetic chemistry. Aswith other free radical reactions ofC-H bonds, some are attacked morereadily than others.13 The Chemistryof the Ether Linkage17 provides de-tails of these reactions and includes an“Appendix on Safety Measures.”

Molecular structure is the primaryfactor in determining the rate of au-toxidation and shelf life within aclass of chemicals.5,6 Peroxide-form-ing compounds invariably containan autooxidizable hydrogen atomthat is activated by adjacent struc-tural components.

Activated hydrogen atoms are oftenon a:

● methylene group adjacent to an ethe-real oxygen atom (-O-CH2 -, e.g. di-ethyl ether, THF, dioxane, diglyme);

● methylene group adjacent to a vinylgroup or benzene ring (C�C-CH2 - orPh-CH2 -, e.g. allyl or benzyl com-pounds);

● CH group adjacent to two etherealoxygen atoms (-O-CH-O-, e.g. acetalsor methylenedioxy compounds);

● CH group adjacent to two methyl-ene groups (-CH2-CH-CH2 -, e.g.isopropyl compounds and decahy-dro- naphthalenes);

● CH group between a benzene ringand a methylene group (-CH2-CH-Ph, e.g. cumene and tetrahydro-naphthalenes);

● a vinyl group (-C�CH2, e.g. vinylcompounds, dienes, styrenes orother monomers).5

Not all compounds containing thesegroups form peroxides. However, thepresence of any of these groups in acompound provide (especially lowmolecular weight) a warning that haz-ardous concentrations of unstableperoxides might be present.4,5 Chem-ical structures that include more thanone of these groups are at particularrisk of peroxidation. For example, vi-nyl groups are increasingly susceptibleto peroxidation when they are further

activated by the addition of an at-tached halogen atom, a phenyl or car-bonyl moiety, or another unsaturatedstructure.17

Within a class of peroxide-formingchemicals, the peroxidation potentialis usually inversely related to the mo-lecular weight of the compound.5,17

One source18 states that compoundswith ten or more carbon atoms at aperoxidizable site are considered low-risk systems, but does not providesupporting data. Kelly7 listed over 125compounds with structural potentialfor undergoing peroxidation.

Autoxidation can be initiated by ul-traviolet light (photoperoxidation), bythe presence of a free radical source,by the peroxide itself, or by impuritiessuch as acetaldehyde. The reactioncannot proceed in the absence ofoxygen or oxidizers. Exposure of sus-ceptible compounds to oxygen alwaysenhances peroxide formation, whereasthe effects of heat, light and contami-nants are variable and unpredictable.Ultraviolet light, including sunlight,promotes both autoxidation and deple-tion of (antioxidant) inhibitors.1,17 Sec-ondary alcohols (e.g., isopropanol,2-butanol) are susceptible to slow per-oxidation and the presence of a ketone(higher than acetone) greatly increasesthe rate and extent of photo-peroxidation. It is likely that similar in-teractions may occur with othercompounds.5,17

The autoxidation reaction proceedsby a free-radical chain mechanismthat usually begins with the abstrac-tion of an active hydrogen from R-Hby the peroxy radical to produce analkyl radical (R*). Oxygen adds to theR* radical to generate the peroxideradical R-O-O*. In almost all cases,the abstraction involves a univalentatom (e.g. hydrogen or halogen). Theabstraction step determines what thechain reaction product will be.13 Forthe substrate R-H, the chain reactioncan be initiated by ultraviolet light, bythe presence of a radical source,and/or by the peroxide itself. Likeother free-radical reactions, the autox-idation process is self-propagating.Organic free radicals are often formedin solution upon heating (in somecases, merely dissolving) a compoundhaving weak covalent bonds.14 Thus,


a single initiating event may lead toself-sustaining reaction with the rateof the peroxide formation increasingwith time.1,13,17

The relatively slow induction periodis often followed by a more rapid ac-cumulation of the corresponding hy-droperoxide. In some cases, hydroper-oxide concentration may reach5–15% and may either stabilize or de-crease as the hydroperoxide decom-poses to form byproducts (e.g. alco-hols and water) that interfere with thefree radical chain reaction and/or per-oxidation. The byproduct content maycontinue to increase while the perox-ide content remains stabile. This sce-nario does not apply when the peroxycompounds crystallize and precipitatefrom the solution. In those cases, theprecipitate remains undiluted by sol-vent or byproducts, and constitutes aserious hazard.8

The degree of peroxide accumula-tion is determined by the equilibriumestablished between peroxide forma-tion and degradation, further reaction,and concentration of the peroxide.The equilibrium varies with com-pound and conditions. The structure-dependent stability of the peroxideproducts varies greatly. For example,�-phenylpropionyl peroxide is so un-stable that it cannot be isolated underambient conditions, whereas t-butylhydroperoxide is stable for weekswhen stored at ambient temperatureand in the dark.4

The hydroperoxide is likely to behighly reactive and usually undergoesfurther addition, rearrangement ordisproportionation leading to dialkyl,polymeric, cyclic, and other unstablehigher peroxide products. These prod-ucts become increasingly dangerouswith heating and/or concentration byevaporation.5,7,17 This is an importantsafety consideration because detec-tion and removal of the intermediatesare more difficult than for simple hy-droperoxides. Rigid adherence to stor-age and handling techniques that arematched to the properties of the ma-terials is critical.7,17

Most alkyl monohydroperoxidesare liquids. The lower members aresoluble in water and are explosive.4

Autoxidation of isopropyl ether formsa variety of higher M.W. peroxides,

including cyclic peroxides of acetone,which may be especially explosivewhen dry. Oxidation of p-dioxaneproduces very dangerous levels (morethan 30% of total peroxide) of diper-oxide products.17

Peroxidation is generally peculiar tothe liquid state. Minimal hazard isusually associated with potential per-oxide formers in the solid or vaporphase. However, the peroxidation re-action can proceed on the surface offinely divided solids.9 Compressedgases (e.g., butadiene, tetrafluoroeth-ylene, vinylacetylene, and vinyl chlo-ride) are relatively resistant to autoxi-dation. However, the difficulty ofcompletely eliminating residual oxy-gen from the receiving vessel increasesthe hazard when the material is trans-ferred to a secondary container. Addi-tion of an appropriate inhibitor to thereceiving container prior to transfercan reduce the risk. Processes involv-ing these gases should be thoroughlyevaluated to determine the likelihoodof forming a liquid phase.7,8

USE AND STORAGE OF PEROXIDE-FORMING SOLVENTSJackson et al.6 categorized laboratorychemicals known to form peroxidesinto Groups A, B, and C (Table 1), onthe basis of their susceptibility to per-oxide formation. (Some monomersidentified by Jackson are no longeravailable in laboratory quantities.)Shelf life (before significant peroxida-tion occurs), and the resulting prod-ucts vary widely between compoundsand storage conditions. The recom-mended maximum shelf life for eachgroup is based upon time after open-ing the container, and is conditionedon the premise that the compoundsare stored in opaque containers underan inert (oxygen-free) atmosphere.Containers of susceptible solvents arenormally supplied with an antioxidantor free-radical scavenger. These inhib-itors can slow, but not prevent peroxi-dation. Therefore, when using theseperoxide-forming reagents, it is criticalto include procedures to guard againstunanticipated results.6,17

Group A includes the chemicalsmost likely to form dangerous levels ofautoxidation products. These chemi-

cals can form explosive peroxide lev-els even in an unopened container,without concentration, and some willseparate from solution. Even low ini-tial concentrations of autoxidationproducts in a solution can be concen-trated to dangerous levels by solventevaporation and may explode uponshaking.5,6 Isopropyl ether is particu-larly dangerous: the presence of twotertiary carbon atoms in the moleculeenhance the tendency to oxidize tothe corresponding hydroperoxide.The hydroperoxide then polymerizesto form a product that precipitatesfrom the ether solution as an explosivecrystalline solid.1,6 The temperatureand concentration at which explosionof peroxides of isopropyl ether be-comes probable has never been au-thoritatively stated.1

Group B includes widely used lab-oratory solvents (e.g., diethyl ether,THF, cyclohexene, the glycol ethers,and isopropanol) that can form explo-sive levels of peroxides. The autoxida-tion products are less volatile than theparent compound, and therefore be-come extremely hazardous whenevaporation concentrates the unstableautoxidation products to increasinglydangerous levels. Most of the solventsin Group B are also volatile so thatrepeated opening of a container mayallow enough evaporation (and expo-sure to atmospheric oxygen) to con-centrate peroxides to a dangerouslevel. It is prudent to test potentialperoxide-formers immediately prior todistillation or evaporation. It can beextremely dangerous to distill or sig-nificantly concentrate any uninhibitedsolvent in Groups A or B unlessknown to be free of peroxidationproducts.1,5,8

Group C includes examples of vinylmonomers that are usually not partic-ularly hazardous. However, they canform peroxides that can initiate explo-sive polymerization (Trommsdorf ef-fect) of the bulk monomer. It is impor-tant to add a suitable polymerizationinhibitor prior to distilling or other-wise concentrating any of thesecompounds.5,9

Although the autoxidation reactionis a relatively slow process (months toyears in some cases), extended storageprovides time for accumulation of un-


stable products. Storage of peroxidiz-able chemicals in open, partiallyempty, or transparent containersgreatly increases the risk of peroxideformation. Peroxidation is acceleratedby heat, light, oxygen or air, and ele-vated temperature. Fluctuations oftemperature and barometric pressurefacilitate infiltration of atmosphericoxygen into the containers. Initial per-oxide buildup is usually slow becausethe exchange of air (containing only20% oxygen) is gradual. A breach ofthe container seal may allow sufficientoxygen to eliminate the inhibitor theninitiate and enhance the autoxidationprocess. Air should always be flushedout of the free space with an inert gas(usually nitrogen) before sealing. Thisis especially critical for the chemicalsin Groups A and B, particularly if theinhibitor has been removed (e.g. dis-tillation) or depleted.1,5

Refrigeration can retard peroxida-

tion of volatile organic peroxidizablecompounds. However, peroxide accu-mulation may actually be enhanced byrefrigeration if the rate of peroxidedegradation is slowed more than therate of peroxide formation. If the sol-vent is held near it’s freezing point,peroxidation products may precipitatefrom solution and become very shocksensitive and dangerous. Some peroxi-dizable organometallic compounds(e.g., Grignard reagents) should not berefrigerated, and there is little or noevidence that refrigeration slows oxi-dation of diethyl ether. The vaporiza-tion of ether may lead to the formationof an explosive atmosphere, even atfreezer temperature.1,5,14 In any case,only completely spark-proof refrigera-tors should be used to store ethers orother volatile peroxide formers.

Laboratory procedures (e.g. evapo-ration, distillation, or spills) that in-crease peroxide concentration or al-

low extensive exposure to air oroxygen are particularly dangerous. Atleast 10% of the bottom residualsshould be retained during distillationor evaporative concentration of anypotential peroxide-former. The hazardcan be reduced by addition of a non-volatile organic liquid (e.g. mineraloil) to the distillation flask. The min-eral oil will remain in the distillationvessel and dilute the remaining perox-ides. It is essential to always include amagnetic stirrer, boiling chips or aninert gas bleed to prevent the localizedconcentration of heat and pressure.Air or other oxygen-containing mix-tures should never be used for mixingduring distillation of potential perox-ide formers.1,6

Peroxide impurities in higher boil-ing point chemicals (e.g. long-chainalkyl ethers and the glycol ethers) usu-ally undergo thermal decompositionat distillation temperatures. However,

Table 1. Potential Peroxide-Forming Chemicals6

GROUP A: Chemicals that form explosive levels of peroxides without concentration. Severe peroxide hazard afterprolonged storage, especially after exposure to air. All have been responsible for fatalities. Test for peroxide formationbefore using or discard after 3 months.

Butadienea Isopropyl ether Sodium amideChloroprenea Potassium amide Tetrafluoroethylenea

Divinyl acetylene Potassium metal Vinylidene chloride

GROUP B: Peroxide hazards on concentration. Test for peroxide formation before distillation or evaporation. Test forperoxide formation or discard after 1 year.

AcetalAcetaldehydeBenzyl alcohol2-Butanol DioxanesChlorofluoroethyleneCumene (isopropylbenzene)Cyclohexene2-Cyclohexen-1-olCyclopenteneDecahydronaphthalene (decalin)Diacetylene (butadiyne)

DicyclopentadieneDiethylene glycol dimethyl-ether (diglyme)Diethyl etherEthylene glycol ether acetates (cellosolves)Furan4-Heptanol2-HexanolMethyl acetylene3-Methyl-1-butanolMethyl-isobutyl ketone4-Methyl-2-pentanol

2-Pentanol4-Penten-1-ol1-Phenylethanol2-PhenylethanolTetrahydrofuranTetrahydronaphthaleneVinyl ethersOther secondary alcohols

GROUP C: Chemicals, which are hazardous due to, peroxide initiation of autopolymerization. The peroxide-formingpotential increases for liquids of this group, especially for butadiene, chloroprene and tetrafluoroethylene, such thatthese materials should be considered as a peroxide hazard. Test for peroxide formation or discard liquids after 6months; discard gases after 1 year.

Butadienea

ChlorobutadieneChloroprenea

Vinyl acetate

ChlorotrifluoroethyleneStyreneTetrafluoroethyleneVinyldiene chloride

Vinyl acetyleneVinyl chlorideVinyl pyridine

a When stored as a liquid monomer. b Can form explosive levels of peroxides when stored as liquid. Peroxide accumulation may causeautopolymerization when stored as gas.


this may not be true in reduced-pres-sure procedures and dangerous perox-ide levels may develop.9

Low levels of free-radical scaven-gers (e.g. 100ppm hydroquinone or di-phenylanine; 2,6-di-tert-butyl-p-meth-ylphenol (BHT); polyhydrophenols,aminophenols and arylamines) aregenerally added to inhibit the chainreaction of the peroxide forming sol-vent. Peroxidation of diethyl ether isinhibited by the addition of iron wireto steel containers. However, iron orother metals will not inhibit peroxida-tion of isopropyl ether and are proba-bly ineffective for other chemicals aswell. In fact, iron may catalyze peroxi-dation in some solvents. One reportindicated that diethyl ether containing10ppm pyrogallol was stabilized forover 2 years. Water can be used todissolve oxidation products but willnot prevent their formation in ethers.Other inhibitors of peroxide forma-tion include Dowex-1 (ethyl ether);hydroquinone (tetrahydrofuran); 100ppm 1-naphthol (isopropyl ether);and stannous chloride or ferrous sul-fate for dioxane. Substituted stil-benequinones have been proposed forstabilization of oxidative deteriorationof ethers and other compounds.1,17

Phenolic compounds are often addedto commercial vinyl monomers. How-ever, phenolic inhibitors are ineffec-tive if some oxygen is not present.Thus, solvents inhibited by thesechemicals should not be stored underinert gas.1,6,14

Antioxidant inhibitors are usuallydepleted as peroxidation products areformed. The inhibitor will eventuallybe depleted to a point that will allowperoxide-formation to proceed asthough uninhibited. When this oc-curs, peroxides may accumulate in amaterial that has been stabilized for along time. The levels of both peroxidesand inhibitor should be monitored, es-pecially if potential peroxide-formersare retained for extended time. Inhib-itor levels must be maintained or thematerial must be treated as though un-inhibited. It is always prudent to usestabilized reagents unless the antioxi-dant interferes with its use. Becausedistillation will separate a stabilizedsolvent from the stabilizer, the distil-late must be stored with care and

closely monitored for peroxide forma-tion. Uninhibited peroxide formersshould not be held over 24 hours.1,7,16

Peroxide-forming compounds shouldbe purchased in limited quantities, usedin order of receipt and never stockpiled.It is prudent to date all chemicals bothwhen they are received and when theyare opened. Peroxide-forming com-pounds should be clearly identified byadditional labeling, and stored in tightlysealed containers (Not with glass stop-pers or screw caps), preferably in thecontainer furnished by the supplier andaway from light and heat. Periodic test-ing to detect peroxides should be per-formed and documented on each con-tainer (especially for compounds inGroups A and B).6,16,17

DETECTION OF PEROXIDESVisual inspection of an organic sol-vent in a glass container can detect thepresence of very high levels of perox-ides. This can be accomplished by us-ing back light or side light with a non-hazardous light source (e.g. aflashlight). Visible indicators of perox-ide presence include:

● Clear liquid containing suspendedwisp-like structures,

● Precipitated crystal formation ap-pearing as chips, ice-like structures,solid mass,

● Appearance of cloudiness,● Gross contamination.

The observation of any of these indi-cators warrants extreme caution. Anycontainer of peroxidizable chemicalsthat is old, deteriorated or of un-known age or history must not bemoved or disturbed (including addi-tional testing). A container must notbe moved or disturbed if there is anyquestion regarding the presence ofperoxides Only individuals with skilland experience in handling extremelyhazardous materials should performhandling and disposal.1,17

A variety of quantitative, semi-quantitative, and qualitative methodsto detect peroxides in organic andaqueous solutions have been devel-oped.19 Kelly7 included detailed pro-cedures for the four most commonlyused semi-quantitative procedures.

These include the iodine detectionmethod (two qualitative variations),the qualitative ferrous thiocyanatemethod, and the use of semiquantita-tive redox dip strips. Alkali metals andtheir amides may form peroxides ontheir surface. DO NOT apply the stan-dard peroxide tests to such materialsbecause they react strongly with waterand oxygen.1

HAZARDOUS LEVELS OF ORGANICPEROXIDESKelly7 reviewed the literature to deter-mine the minimum hazardous con-centration of peroxides in solutionwith organic solvents. Peroxide con-centration of 100 ppm has beenwidely used as a control point, butlacks scientific validation and is prob-ably based on the practical detectionlimit of the potassium iodide method.Kelly reported great disparity (range50–10,000 ppm as hydrogen peroxide)between various references. There waslittle agreement between authors andnone provided supporting data. Thehighest level (10,000-ppm) was foundin a National Safety Council publica-tion. However, the NSC publicationincluded neither supporting refer-ences for the latter statement nor forthe recommendation for administra-tive control value of 100 ppm.7,18

The Material Safety Data Sheet fordiethyl ether cautions against concen-trating ether containing peroxide lev-els above 100-ppm.16 Presumably, theconcentration of unstable oxidationproducts increases to a point at whichthe solution spontaneously explodes.Kelly suggested that it is likely that thecontrol concentration of 100 ppmmay, in some cases, be overly conser-vative by at least an order of magni-tude. This may especially apply to theGroup B chemicals listed in Table 1,unless the unstable materials are con-centrated as result of solvent evap-oration.7

Kelly7 stated that “theoretically, ex-plosion should be impossible for mostsolutions containing �1% peroxides.”However, establishment of a safe con-centration may be complicated by cir-cumstances that allow the unstablematerial to be concentrated throughsome mechanism such as evaporation.


A dilute solution of most peroxidiz-able chemicals, or a solutions in a sol-vent with low volatility (B.P. � 300° Cor V.P. �0.1 mm Hg at 20° C) are notlikely to concentrate and do not usu-ally pose a peroxide hazard.1,7

CLEANUP AND DISPOSAL OFPEROXIDES AND PEROXIDE-FORMING CHEMICALS

Handling, storage, and disposal proce-dures are dictated by the physical andchemical characteristics of the particu-lar material. Vessels containing hazard-ous or suspicious materials should notbe handled directly. Remote handling(e.g., tongs), personal protective equip-ment (e.g., gloves, face and eye protec-tion, etc) and explosion-proof barri-cades (including the fume hood sash)should be used to minimize close con-tact with reactants, reaction mixture orproducts. It is useful to be mindful ofthe inverse square law when designinglaboratory work with hazardous mate-rials. The blast effect from small chargesattenuates very rapidly in the open. Thesafest practical peroxide compositionshould be selected for each use.1

● Never attempt to force open arusted or stuck cap on a container ofa peroxide-forming chemical.

● Never attempt to clean by scrapingor rubbing glassware or other con-tainers that may contain peroxidesor peroxide-forming materials.

Liquid peroxides do not readily ignite,but once ignited the burn rate in-creases as the fire progresses. Sponta-neous combustion can occur uponcontact of the peroxide with combus-tible materials. Solid organic perox-ides ignite more readily and burn withincreasing rate as the fire progresses.Contact with finely divided combusti-ble material may produce an explosivemixture. Because of the extreme sen-sitivity of solid per-compounds toshock and friction, they might ignitefrom friction or upon contact with theoils on shoe soles. Therefore, workersmust not be allowed to walk through aspill. Emergency responders and firefighters should be aware of the specialcare required when organic peroxidesare involved. Spills on clothing consti-

tute a significant fire risk as well assevere dermal irritation or burn. Con-taminated clothing should be changedimmediately and thoroughly laun-dered (solvent or alkaline water wash-ing) before storage or return to use.20

Pure peroxides must be dilutedprior to disposal and should never bedisposed of directly. In some casessmall quantities (�25 g) of peroxidescan be diluted with water to a concen-tration of 2% or less, then transferredto a plastic container containing anaqueous solution of a reducing agentsuch as ferrous sulfate or sodiumbisulfite. The material can then behandled like any other hazardouschemical waste. However, it must notbe co-mingled with other chemicalwaste. Larger quantities of organicperoxide may require special handlingby well-trained personnel. Empty con-tainers of peroxides or peroxide-form-ers can be discarded in regular trashafter triple rinsing with water and de-facing or removal of the label.20

Spilled peroxides should be absorbedon vermiculate as soon as possible. Ifappropriate facilities are available, thevermiculate-peroxide mixture can be in-cinerated directly or may be slurried bystirring with a suitable solvent. Theslurry can be treated with an acidic fer-rous sulfate solution (60 g ferrous sul-fate � 6 mL con sulfuric acid � 110 mLwater). Never flush organic peroxidesdown the drain.20

Special transportation proceduresare necessary because of the flamma-bility and explosiveness of organicperoxides. Most organic peroxides canbe shipped at ambient temperature,but some require refrigeration. (See“Storage of Organic Peroxides andPer-Compounds”). Failure of the re-frigeration system can result in de-composition and fire.

CONCLUSIONSPeroxides and peroxide-forming or-ganic solvents are commonly found inchemistry laboratories and lab person-nel may not be aware of their presenceor of the associated hazards. Ethers areof greatest concern due to their omni-presence in laboratories and the easewith which they form peroxides. In-structors, stockroom attendants and re-

searchers alike must consider the haz-ards associated with other potentialperoxide-forming organic compounds.The instability of peroxides slowlyformed in organic compounds in thepresence of oxygen is preventable bystorage and handling techniques thatare accurately matched to the propertiesof the material concerned.

The need to use peroxides and per-oxide-forming organic compoundsshould be carefully evaluated andtheir use should be avoided or mini-mized whenever possible. If use is un-avoidable, appropriate testing and de-contamination of questionablereagents is essential. The safe use ofthese materials require a chemicalfume hood and personal protectiveequipment such as properly selectedgloves, clothing, eyewear, and faceshields. Procedures that include heat-ing, distillation, or evaporation ofthese substances warrant extra pre-cautions. These procedures must al-ways be conducted within a chemicalfume with the hood sash positioned aslow as possible. The need for explo-sion shielding should be seriouslyconsidered.

Chemical reactions involving per-oxides can be conducted safely by ex-perienced personnel following goodlaboratory techniques and prudentpractices. Initial or unfamiliar reac-tions should be limited to minimalquantities (� 1 g). Review of the prop-erties of analogous materials can pro-vide valuable guidance in determininghazard of new or unfamiliar reagentsor procedures. Although the pattern isnot necessarily predictable, reactivityalways increases with increased ac-tive-oxygen content of a molecule.Virtually all organic peroxides becomeless prone to violent reaction if di-luted. The reaction mixture can be de-activated by addition of a large excessof aqueous sodium hydroxide. Mix-tures of concentrated hydrogen perox-ide and organic substances can reactto produce powerful and sensitive ex-plosives. This is extremely importantin organic syntheses involving hydro-gen peroxide.

The hazards and consequences offires and explosions during the labora-tory use of organic peroxides are widelyrecognized. There is no way to assure,


with any degree of certainty that acci-dental explosions will not occur whenworking with such reactive and poten-tially dangerous materials. Spontaneousor induced decomposition may culmi-nate in a variety of ways, ranging frommoderate gassing to spontaneous igni-tion or explosion. The failure to recog-nize the effect of physical and chemicalfactors associated with reaction kineticsis often the root-cause of unexpectedviolent chemical reactions. Reactantconcentration and temperature controlare critical the for control of reactionrate.1

References1. Shanley, E. S. Organic Peroxides: Eval-

uation and Management of Hazards,Chapter V in “Organic Peroxides,”Volume III, Daniel Swern, Ed., WileyInterscience Publishers, New York,1972.

2. Curci, R. and Edwards, J. O., PeroxideReaction Mechanisms – Polar, ChapterIV in Volume I, Daniel Swern, Ed.,Wiley Interscience Publishers, NewYork, 1970.

3. Schultz, M. and Kirschke, K., CyclicPeroxides, Chapter II in “Organic Per-oxides,” Volume III, Daniel Swern,Ed., Wiley Interscience Publishers,New York, 1972.

4. Mageli, O. L. and Sheppard, C. S., Or-ganic Peroxides and Peroxy Com-pounds - General Description, Chapter1 in “Organic Peroxides,” Volume I,Daniel Swern, Ed., Wiley IntersciencePublishers, New York, 1970.

5. Bretherick, L., in Improving Safety inthe Chemical Laboratory: A PracticalGuide, J. A. Young, Editor, John Wiley& Sons, New York, 1987.

6. Jackson, H. L., McCormack, W. B.,Rondestvedt, C. S., Smeltz, K. C., andViele, I. E., Control of PeroxidizableCompounds, J. Chem. Educ., 1970,46(3), A175 .

7. Kelly, R. J., Review of Safety Guide-lines for Peroxidizable Organic Com-pounds, Chemical Health & Safety,1996, 3(5) 28–36.

8. American Chemical Society Commit-tee on Chemical Safety, Safety in Aca-demic Chemistry Laboratories, 6thEdition, American Chemical Society,Washington, D. C., 1995.

9. CRC Handbook of Laboratory Safety,5th Edition, A. K. Furr, Editor, CRCPress, Boca Raton, 2000.

10. Mahn, W. J., Academic LaboratoryChemical Hazards Guidebook, Nos-trand Reinhold, New York, 1990.

11. Long, J. R., Chem. & Eng. News, 2000,78(19) 8.

12. Registry of Toxic Effects of Chemical

Substances (RTECS), http://hazard.com/msds/tox.html

13. March, J., Advanced Organic Chemistry:Reactions, Mechanisms, and Structure,5th ed., John Wiley, New York, 1992.

14. Pepitone, D. A., Ed., Safe Storage ofLaboratory Chemicals, John Wiley &Sons, New York, 1984.

15. Ashland Chemical Company, http://www.ashchem.com/ehs/prostewop_i.html

16. National Research Council, PrudentPractices in the Laboratory: Handlingand Disposal of Chemicals; NationalAcademy Press, Washington, 1995.

17. Steere, N. V, Appendix on Safety Mea-sures, Chapter 16 in The Chemistry ofthe Ether Linkage, Saul Patai, Editor,Wiley Interscience Publishers, NewYork, 1967.

18. National Safety Council, Recognitionand Handling of Peroxidizable Com-pounds, 1987, Data Sheet I-655-Rev.87; Chicago.

19. Mair, R. D. and Hall, R. T., Determina-tion of Organic Peroxides by Physical,Chemical and Colorimetric Methods,Chapter VI in “Organic Peroxides,” Vol-ume II, Daniel Swern, Ed., Wiley Inter-science Publishers, New York, 1972.

20. Hall, Stephen K., Chemical Safety inthe Laboratory, Lewis Publishers,Boca Raton, FL, 1994.


Appendix I. Safety Guidelines for Handling Organic Peroxides(17,22)

● Purchase and use only the minimum quantity required.● Wear nitrile gloves, eye protection and body protection such as a lab coat or

apron.● Conduct procedures inside a chemical fume hood or behind a protective

shield.● Do not return unused peroxides to the container.● Clean up liquid spills immediately. Dispose promptly as hazardous waste.

See Armour23 for recommended procedures for specific compounds.● Avoid using solutions of peroxides in volatile solvents. Solvent evaporation

should be controlled to avoid dangerous concentration of the peroxide.● Do not allow peroxides to contact iron or compounds of iron, cobalt, or

copper, metal oxide salts, acids or bases, or acetone.● Use plastic (not metal) spatulas to handle peroxides.● Do not allow open flames, or other sources of heat, sparks, friction, grinding

or forms of impact near peroxides.● Do not use glass containers with screw-cap lids or glass stoppers. Use

polyethylene containers with polyethylene screw caps or stoppers.● Protect from heat and light.● Store peroxides at the lowest possible temperature consistent with their

solubility and freezing point.● Long term storage (e.g., greater than one year) should be avoided.● Refrigerated storage of peroxides or other flammable chemicals must be

ONLY in “Lab-Safe” or explosion-proof units

Appendix II. Safety Checklist forChemical Reactions Involving Perox-ides

❑ temperature control and heatdissipation mechanism areappropriate for liquid and vaporphases;

❑ correct proportion andconcentration of catalyst andreactants are used;

❑ purity of components (absence ofcatalytic impurities) is assured;

❑ the reaction solvent is appropriatefor the reaction conditions;

❑ the viscosity of the reactionmedium is appropriate;

❑ the rate of reactant combination isappropriate for the conditions

❑ an appropriate induction period isincluded;

❑ the procedure includesappropriate stirring or agitation(mechanism, degree)

❑ the reaction atmosphere iscontrolled;

❑ appropriate pressure release andcontrols are incorporated into thesystem;

❑ conditions that might causeignition, decomposition, (e.g.actinic radiation) of unstablematerials are avoided;

❑ shielding and personal protectiondevices are in place.


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Peroxides and peroxide-forming compounds