Peroxide Forming Chemicals

Materials that are susceptible to peroxide formation (i.e., autooxidation) are ones that typically react with air, moisture or impurities and produce a change in their chemical composition in normal storage. The peroxides that form are less volatile than the solvent itself and thus tend to concentrate. This is particularly dangerous if peroxides are present during a distillation, where the applied heat to the concentrated solution may trigger a violent explosion. Equally dangerous is to allow a container of this material to evaporate to dryness, leaving the crystals of peroxide at the bottom of the container.

Chemicals that are sensitive to peroxide formation can be broken into three categories (Jackson, J. Chem. Ed., 1970) as shown in the following table.

A.  	Peroxide hazard after prolonged storage.  Form potentially explosive peroxides 
	without concentrating.  
	All have been responsible for fatalities.  
	Test for peroxide formation or discard after 3 months.

	isopropyl ether 		divinyl acetylene
	potassium metal			potassium amide
	sodium amide			vinylidene chloride
	

B. 	Chemicals which become a peroxide hazard if concentrated, such as through 
	distillation or evaporation.  
	Test for peroxide formation or discard after 1 year.

	dioxane				diethyl ether
	tetrahydrofuran			acetal
	cumene				cyclohexane
	cyclopentene			diacetylene
	dicyclopentadiene		ethylene glycol dimethyl ether
	furan				methyl acetylene
	methyl cyclopentane		methyl-isobutyl ketone
	tetrahydronaphthalene		vinyl ethers
	

C. 	Chemicals which are a hazard due to peroxide initiation of polymerization.  
	The peroxide forming potential increases for liquids of this group.  
	Test for peroxide formation or discard after 1 year.

	butadiene			chlorobutadiene
	chlorotrifluoroethylene		styrene
	tetrafluoroethylene		vinyl acetate
	vinyl acetylene			vinyl chloride
	vinyl pyridine			acrylonitrile

The materials in group A are particularly hazardous and are capable of forming peroxides that may explode even without undergoing distillation or evaporation. One of the more dangerous is isopropyl ether, which decomposes rapidly on storage so that crystals of peroxides accumulate in the threads under the cap. This condition is extremely dangerous and the container should not be opened - friction may initiate detonation. Materials discovered in this condition may need to be removed by a bomb squad from the local fire department. These chemicals should never be stored for longer than 3 months; after this time they should be discarded without opening or should be tested for peroxide formation. Any container that has been stored for greater than 6 months should be approached with extreme caution.

The chemicals in groups B and C should be discarded or tested for peroxide formation after 12 months.

If the age of any of these compounds is unknown, or is suspected to be greater than these recommended time frames, the container should not be opened.

Detection of Peroxide Formation in Laboratory Chemicals

A simple qualitative test can be performed on peroxide forming compounds to test for peroxide content. This test is based on the oxidation of iodide ion to iodine and is accomplished by adding 1 mL of the substance to be tested to a freshly prepared solution of 100 mg of sodium or potassium iodide in 1 mL of glacial acetic acid. A yellow color indicates a low concentration of peroxide in the sample; a brown color indicates a high concentration. This test is sensitive to the formation of hydroperoxides (ROOH), which is the principal hazard associated with peroxide-forming solvents, but does not detect difficult to reduce peroxides such as dialkyl peroxides (ROOR). This type of peroxide can be detected by a reagent consisting of 3 g of sodium iodide dissolved in 50 mL of glacial acetic acid and adding 2 mL of 37% hydrochloric acid.

More recently, test strips have been developed that will test for the presence of peroxides in a much more straightforward fashion.

Precautions for Handling Peroxide Forming Materials

• Minimize the quantity of peroxides kept in the lab.
• Carefully review all cautionary material supplied by the manufacturer prior to use.
• Segregate these compounds from others that could create a serious hazard to life or property should an accident occur.
• Never return unused quantities back to the container (contamination!).
• Cleanup all spills immediately.
• Dilution of the organic peroxide with the appropriate inert solvent (aliphatic hydrocarbons, as an example) helps to reduce the sensitivity of the peroxide to shock and heat.
• Avoid evaporation or distillation!
• Avoid contact with any metal source, such as spatulas, because metals can promote explosive decomposition. Use wood or ceramic instead.
• Ignition sources in the area of peroxide use must be prohibited.
• All sources of friction and grinding must be avoided. This includes the use of glass containers with screw on caps (crystals may form in the threads) or glass stoppers (glass against glass friction).
• Store peroxides at the lowest possible temperature consistent with their solubility or freezing point. Do not freeze or cause the peroxide to precipitate out, however, since this is the most dangerous state!

  

  
  
  

  Created and maintained by Nancy Magnussen
  last revised 1 Dec 1997
  nancy@isc.tamu.edu

  
  
  

  Copyright © 1996 by College of Science, Texas A&M University