Organic Peroxides and Peroxide Formers

Chemicals containing the bivalent –O-O- structure, which is a structural derivative of hydrogen peroxide (H2O2) where one or both hydrogen atoms are replaced by an organic radical, are organic peroxides. These compounds are reactive and unstable because of shock, pressure, or temperature.

Peroxides can be highly reactive, powerful oxidizers, and highly flammable. The oxygen-oxygen bond is a weak bond and can be cleaved from the energy generated from mechanical shock, heat, light, or chemical contact.

Free radicals are formed from the broken oxygen – oxygen bond. The free radicals are highly reactive and a large amount of energy is released during the decomposition of the chemical.

The are generally three classes of chemicals that can form peroxides. The degree of explosion hazard depends on the the chemical, condition in which it is stored and the conditions in which it is used.

Class A

Peroxidizable compounds which form explosive compounds without being

concentrated.

Organic Inorganic
Divinyl ether Potassium metal
Divinyl actylene Potassium Amide
Isopropyl ether Sodium amide (sodamide)
Vinylidene  

 

Class B

Chemicals that present a peroxide hazard when they are concentrated via
distillation or evaporation. Specific distillation and evaporation procedures
must be performed.
Acetal Dioxane (p-dioxane)
Cumene Ethylene glycol dimethyl ether (glyme)
Cyclohexene Furan
Cyclooctene Methyl acetylene
Cyclopentene Methyl cyclopentane
Diacetylene Methyl-i-butyl ketone
Dicyclopentadiene Tetrahydrofuran
Diethylene glycol dimethyle ether Tetrahydronaphthalene
Diethyl ether Vinyl ethers

 

Class C

Unsaturated materials that may polymerize violently and hazardously due to
peroxide initiation.
Acrylic acid Tetrafluoroethylene
Acrylonitrile Vinyl acetate
Butadiene Vinyl acetylene
Chlorobutadiene (Chloroprene) Vinyl chloride
Chlorotrifluoroethylene Vinyl pyridine
Methyl methacrylate Vinylidene chloride
Styrene  

Testing for the Presence of Peroxides

Class A, B, and C must be tested for the presence of peroxides every three months. The chemical must be either re-dated as safe if no peroxides are present or disposed of through the University's Hazardous Waste Program.

Aqueous Peroxide Test Method
1. Add 1 to 3 mL of liquid to be tested in an equal volume of acetic acid.
2. Add a few drops of 5% aqueous potassium iodide solution
3. Stir. Do not let the mixture touch your skin.
         
  The appearance of a yellow to brown color indicates the presence of peroxides.
         
  A yellow color indicates a low concentration of peroxides (less than 100 ppm). A brown color indicates a high concentration of peroxides (greater than 100 ppm).
         
    Chemicals containing concentrations below 100 ppm, may be treated with remove the peroxide contamination and stored for future use. Refer to the peroxide treatment section for details.
    Chemicals containing more than 100 ppm of peroxides must be disposed of immediately through the University's Hazardous Waste Program. Contact 372-2171 for more information.
         
         
Peroxide Test Strips
1. Use a peroxide test strip to test for the presence of peroxides.
         
    Chemicals containing concentrations below 100 ppm, may be treated with remove the peroxide contamination and stored for future use. Refer to the peroxide treatment section for details.
    Chemicals containing more than 100 ppm of peroxides must be disposed of immediately through the University's Hazardous Waste Program. Contact 372-2171 for more information.


Removal of Peroxides

This procedure must only be used for chemical solutions that contain less then 100 ppm of peroxides. Solutions greater then 100 ppm must be disposed of through the University's Hazardous Waste Program.

Activated Alumina Column Removal
1. Prepare a column of activated alumina.
2.

Poor the peroxide containing solution through the column.
- Do not allow the column to dry out while in use.

3. Re-test for the presence of peroxides. If peroxides are still present, pass it through the column until you can not detect them.
4. When the alumna column is no longer effective at removing the peroxides, wash the column with 5% aqueous aqueous ferrous sulfate and discard the solution as hazardous waste.

Distillation and Evaporation Procedures

This procedure must be used for Class A, B, and C materials.

1. Test for the presence of peroxides.
- If greater then 100 ppm, then discard as hazardous waste.
- If less then 100ppm, treat until you cannot detect the presence of peroxides
2. Before distilling any Class C material, a suitable polymerization inhibitor must be added.
3. An explosion shield must be used and placed between the evaporation or distillation process and the operator.
4. Safety goggles must be worn by the operator.
5. Evaporate or distill and leave at least 10% of the solution in the container. Most accidents occur when material is almost or a nearly dry residue.
       
    Use a boiling aid or magnetic stirrer before you use a nitrogen bleed to maintain ebullition.
    In operations using higher boiling peroxidizable compounds under reduced pressure, and explosive mixture can result because the boiling temperature may be lower then the peroxide decomposition temperature. Contact Environmental Health and Safety (372-2171) when performing an operation of this type.


References

Atkins, P.W.: The Elements of Physical Chemistry. Oxford University Press, 1993.

Fox, M.A., Whitesell, J.K: Organic Chemistry. Boston: Jones and Bartlett Publishers, 1994.

Jackson, H.L., McCormack, W.B., Rondestved, C.S., Smeltz, K.C., Viele I.E.: Control of Peroxidizable Compounds. Journal of Chemical Education 47(3) A175-A188, 1970.

National Research Council: Prudent Practices in the Laboratory: Handling and Disposal of Chemicals. Washington D.C.: National Academy Press, 1995.

Williamson, K.L.: Macroscale and Microscale Organic Experiments, 2nd ed. Lexington MA: D. C. Heath and Company, 1994.