safety-in-academic-chemistry-laboratories-students

Peroxides have a specific half life or rate of

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Unformatted text preview: handled in laboratories are more sensitive to shock than primary explosives such as TNT. Peroxides have a specific half-life, or rate of decomposition, under any given set of conditions. A low rate of decomposition may autoaccelerate into a violent explosion, especially in bulk quantities of peroxides. They are sensitive to heat, friction, impact, light, and strong oxidizing and reducing agents. Never open a container if you suspect that the contents are contaminated with a peroxide—the contents may explode. All organic peroxides are extremely flammable, and fires involving bulk quantities of peroxides should be approached with extreme caution. A peroxide present as a contaminating reagent in a solvent can change the course of a planned reaction. The following types of compounds form peroxides: ● Aldehydes. ● Ethers, especially cyclic ethers, and ethers derived from primary and secondary alcohols. It is especially important to label the containers of ethyl or isopropyl ether with the date they are received, so that the user can destroy the contents of the container within three months after receipt. Never distill an ether unless it is known for certain to be free of peroxides, and even then do not distill to dryness. ● Compounds containing benzylic hydrogen atoms. Such compounds are especially susceptible to peroxide formation if the hydrogens are on tertiary carbon atoms [e.g., cumene (isopropyl benzene)]. ● Compounds containing the allylic (CH2 = CHCH2 –) structure, including most alkenes. ● Ketones, especially cyclic ketones. ● Vinyl and vinylidene compounds (e.g., vinyl acetate and vinylidene chloride). 24 students short index 1/15/03 12:45 PM Page 25 Examples of chemicals that can form dangerous concentrations of peroxides when exposed to air: ● Cyclohexene ● Cyclooctene ● Decalin (decahydronaphthalene) ● p-Dioxane ● Ethyl ether ● Isopropyl ether ●T etrahydrofuran (THF) ● Tetralin (tetrahydronaphthalene) Be sure that your instructor knows in advance if you plan to work with any of these compounds. 25 students short index 1/15/03 12:45 PM Page 26 3. Recommended Laboratory Techniques...
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This document was uploaded on 02/27/2014 for the course PHYS 1B at UCSD.

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