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.