Peroxide Forming Chemicals

Several organic solvents over time undergo auto-oxidation to produce unstable peroxides and hydroperoxides. Some peroxide forming solvents contain a peroxide inhibitor to reduce the auto-oxidation process. While solvents containing peroxide forming inhibitor undergo slower oxidation, they will still form peroxides over time. Under normal storage conditions peroxide forming solvents slowly begin to accumulate peroxides in the container. Peroxides are capable of causing serious injury and even fatalities because of their highly unstable nature. They can explode violently when subjected to light, heat, friction or mechanical shock.

Some of the potential peroxide formers organic groups are listed below. However, ethers are the most notorious peroxide former functional group and most commonly used in research and teaching operations. Other peroxidizable organic materials include acetals, allyic alkenes, chloro- and fluoroalkenes, dienes, aldehydes, amides, lactams, ureas, alkylarenes with tertiary α hydrogen, ketones, vinyl monomers, and secondary alcohols.

Peroxide formers are classified into four different categories:

Class A peroxide formers:

Spontaneously decompose and become explosive with exposure to air without concentration. These are the most hazardous and can form explosive peroxide levels even if not opened. Discard after 3 months of receiving these chemicals. 

Butadiene (liquid monomer)

Isopropyl ether

Sodium amide (sodamide)

Chloroprene (liquid monomer)

Potassium amide

Tetrafluoroethylene (liquid monomer)

Divinyl ether

Potassium metal

Vinylidene chloride

Class B peroxide formers:

Chemicals that form explosive levels of peroxides after concentration. Require external energy for spontaneous decomposition. Form explosive peroxides when distilled, evaporated or otherwise concentrated.

Acetal

Diethylene glycol dimethyl ether (diglyme)

4-Methyl-2-pentanol

Acetaldehyde

Diethyl ether (ether)

2-Pentanol

Benzyl alcohol

Dioxanes

4-Penten-1-ol

2-Butanol

Ethylene glycol ether acetates (glyme)

1-Phenylethanol

Cumene

Furan

2-Phenylethanol

Cyclohexanol

4-Heptanol

Tetrahydrofuran (THF)

Cyclohexene

2-Hexanol

Tetrahydronaphthalene (tetralin)

2-Cyclohexen-1-ol

Methylacetylene (gas)

Vinyl ethers

Decahydronaphthalene (decalin)

3-Methyl-1-butanol

Other secondary alcohols

Diacetylene (butadine, gas)

Methyl cyclopentane

 

Dicyclopentadiene

Methyl isobutyl ketone

 

Class C peroxide formers:

Highly reactive and can auto-polymerize as a result of internal peroxide accumulation. The peroxides formed in these reactions are extremely shock- and heat-sensitive. These materials are typically stored with polymerization inhibitors to prevent the polymerization reactions. 

Acrylic acid

Chlorotrifluoroethylene (gas)

Vinylacetylene (gas)

Acrylonitrile

Methyl methacrylate

Vinyladiene chloride

Butadiene (gas)

Styrene

Vinyl chloride (gas)

Chlorobutadiene

Tetrafluoroethylene (gas)

Vinyl pyridine

Chloroprene

Vinyl acetate

 

Class D peroxide formers:

Chemicals that may form peroxides but cannot clearly be placed in Classes A through C.

Acrolein

p-Chlorophenetole

4,5-Hexadien-2-yn-1-ol

Allyl ether

Cyclooctene

n-Hexyl ether

Allyl ethyl ether

Cyclopropyl methyl ether

o.p-Iodophenetole

Allyl phenyl ether

Diallyl ether

Isoamyl benzyl ether

p-(n-Amyloxy)benzoyl chloride

p-Di-n-butoxybenzene

Isoamyl ether

n-Amyl ether

1,2-Dibenzyloxyethane

Isobutyl vinyl ether

Benzyl n-butyl ether

p-Dibenzyloxybenzene

Isophorone

Benzyl ether

1,2-Dichloroethyl ethyl ether

b-Isopropoxypropionitrile

Benzyl ethyl ether

2,4-Dichlorophenetole

Isopropyl-2,4,5-trichlorophenoxy acetate

Benzyl methyl ether

Diethoxymethane

n-Methylphenetole

Benzyl-1-naphthyl ether

2,2-Diethoxypropane

2-Methyltetrahydrofuran

1,2-Bis(2-chloroethoxyl)ethane

Diethyl ethoxymethylenemalonate

3-Methoxy-1-butyl acetate

Bis(2-ethoxyethyl)ether

Diethyl fumarate

2-Methoxyethanol

Bis(2-(methoxyethoxy)ethyl) ether

Diethyl acetal

2-Methoxyethyl acetate

Bis(2-chloroethyl) ether

Diethylketene

3-Methoxybutyl acetate

Bis(2-ethoxyethyl) adipate

Diethoxybenzene (m-,o-,p-)

2-Methoxyethyl vinyl ether

Bis(2-methoxyethyl) carbonate

1,2-Diethoxyethane

Methoxy-1,3,5,7-cyclooctatetraene

Bis(2-methoxyethyl) ether

Dimethoxymethane

b-Methoxypropionitrile

Bis(2-methoxyethyl) phthalate

1,1-Dimethoxyethane

m-Nitrophenetole

Bis(2-methoxymethyl) adipate

Di(1-propynl) ether

1-Octene

Bis(2-n-butoxyethyl) phthalate

Di(2-propynl) ether

Oxybis(2-ethyl acetate)

Bis(2-phenoxyethyl) ether

Di-n-propoxymethane

Oxybis(2-ethyl benzoate)

Bis(4-chlorobutyl) ether

1,2-Epoxy-3-isopropoxypropane

b,b-Oxydipropionitrile

Bis(chloromethyl) ether

1,2-Epoxy-3-phenoxypropane

1-Pentene

2-Bromomethyl ethyl ether

p-Ethoxyacetophenone

Phenoxyacetyl chloride

beta-Bromophenetole

1-(2-Ethoxyethoxy)ethyl acetate

a-Phenoxypropionyl chloride

o-Bromophenetole

2-Ethoxyethyl acetate

Phenyl-o-propyl ether

p-Bromophenetole

(2-Ethoxyethyl)-a-benzoyl benzoate

p-Phenylphenetone

3-Bromopropyl phenyl ether

1-Ethoxynaphthalene

n-Propyl ether

tert-Butyl methyl ether

o,p-Ethoxyphenyl isocyanate

n-Propyl isopropyl ether

n-Butyl phenyl ether

1-Ethoxy-2-propyne

Sodium 8-11-14-eicosatetraenoate

n-Butyl vinyl ether

3-Ethoxypropionitrile

Sodium ethoxyacetylide

Chloroacetaldehyde diethylacetal

2-Ethylacrylaldehyde oxime

Tetrahydropyran

2-Chlorobutadiene

2-Ethylbutanol

Triethylene glycol diacetate

1-(2-Chloroethoxy)-2-phenoxyethane

Ethyl-b-ethoxypropionate

Triethylene glycol dipropionate

Chloroethylene

Ethylene glycol monomethyl ether

1,3,3-Trimethoxypropene

Chloromethyl methyl ether

2-Ethylhexanal

1,1,2,3-Tetrachloro-1,3-butadiene

beta-Chlorophenetole

Ethyl vinyl ether

4-Vinyl cyclohexene

o-Chlorophenol

2,5-Hexadiyn-1-ol

Vinylene carbonate

Minimizing the hazards of peroxide forming chemicals

Researchers using these peroxide formers must learn to safely handle these compounds. Safe handling procedures are guided by having an effective storage control program, periodically testing for peroxides (only if properly trained), enforcing proper disposal procedures, and making effective purchasing decisions.

Disposal

ALL peroxide formers must be disposed through EHS if they’ve been open for greater than 6 months, unopened for more than one year, or are past the manufacturer’s expiration date (Class A peroxide formers should be disposed of earlier). Testing for peroxides in some cases may be useful. Personnel doing the testing should be knowledgeable and experienced in testing for peroxides. The testing method must be described in writing with the associated test results. 

Peroxide Levels Assessment:

  • < 25 ppm Considered safe for general use
  • 25 – 100 ppm Not recommended for distilling or otherwise concentrating
  • 100 ppm Avoid handling and contact EHS immediately to arrange disposal

General Precautions

Minimize the quantity of peroxide formers and peroxides in the lab.

Label each container with date received, date opened, and date tested (if applicable).

Segregate the compounds from incompatible materials. Store away from ignition sources. Protect from heat, flame, friction, shock, and static electricity.

Always perform a peroxide test before doing distillation or purification of peroxide formers.

Use extreme caution before concentrating or purifying peroxide forming chemicals because the majority of peroxide-related explosions occur during this process.

Wear proper PPE including gloves, safety glasses or goggles, face shield, and a flame-retardant lab coat.

Never distill peroxide forming chemicals to be completely dry. Always leave a minimum of 20% of the chemicals in the still.

Tightly seal open containers and store in a cool place away from light, heat and ignition sources.

If solid crystal is observed during visual inspection of the peroxide former containers or around the cap of the container do not move or open the container. Immediately contact EHS for disposal.

Design your experiment to use the least amount of material possible to achieve the desired result.

Do not exceed the scale of the experiment without authorization and approval of the PI.

Do not use metal spatulas to handle solid peroxides. Ceramic, teflon, or wooden spatulas may be used if they do not generate a static charge.