Morris Kharasch – discoverer of peroxide effect - WorldOfChemicals

Morris Kharasch – discoverer of peroxide effect

Category : Personalities
Published by : Data Research Analyst, Worldofchemicals.com

Biography & Contributions

Morris Kharasch [Morris Selig Kharasch] was organic chemist born on August 24, 1895 - October 9, 1957. Kharasch is remembering for his discoveries of free radicals addition reaction and polymerization process.

He synthesized an important anti-microbial alkyl mercuric sulfur compound, thimerosal. Kharasch applied his knowledge of radical reactions to aid in the polymerization of synthetic styrene. He proposed that the anti-Markovnikov addition of HBr to allyl bromide to yield 1,3-dibromopropane was due to the presence of peroxides. He termed this the "peroxide effect", which he proposed proceeds through a free radical chain reaction addition.

Kharasch hypothesized that the rapid anti-Markovnikov addition of HBr to allyl bromide was the result of trace amounts of peroxide in the reaction mixture that could have resulted from the interaction of molecular oxygen in its diradical triplet state and allyl bromide to form allyl bromide peroxide.

Kharasch also supported the idea of a peroxide-induced chain reaction by showing that the addition of antioxidants to the reaction mixture caused the reaction to proceed in aerobic conditions much as it would have if it were in vacuo, producing the slowly forming 1,2-dibromopropane. The function of an antioxidant is to act as a radical scavenger, either accepting or donating an electron to a radical species. Thus the radical becomes effectively neutralized, while the antioxidant itself becomes a radical. Kharasch’s research works helped to discovering mass production of synthetic rubber and plastics.

Thiomersal Properties

Thiomersal is an organomercury compound. It has been used as a preservative in vaccines, immunoglobulin preparations, skin test antigens, antivenins, ophthalmic and nasal products, and tattoo inks. Thiomersal’s main use is as an antiseptic and antifungal agent.

Styrene

Styrene occurs naturally in small quantities in some plants and foods and is also found in coal tar. It is a derivative of benzene is a colorless oily liquid that evaporates easily and has a sweet smell, although high concentrations confer a less pleasant odor. Styrene is named for styrax balsam, the resin of Liquidambar trees of the Hamamelidaceae plant family. Styrene is commonly produced by the catalytic dehydrogenation of ethylbenzene.

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