Radical start agent

The compound which the radical start agent (radical かいしざい, radical initiator) is the reaction condition that is mild to push forward a radical reaction, and produces a radical. The radical start agent has small weak combination of the binding energy generally. I am used as a polymerization initiator in the radical polymerization reaction that is high polymer exclusive law of the synthesis industrially. I can classify it in some types as follows.

Table of contents

Dihalogen

The dihalogen molecules are divided into two halogen atom radicals by halogen - halogen-binding homolysis. From chlorine molecules (Cl₂), for example, radical two chlorine by the irradiation of ultraviolet rays (Cl•) occurs. This is used by halogenation of alkane.

Azo compound

Azo compound (R-N=N-R) disintegrates to two carbon radicals and nitrogen molecules by heat or light. For example, azo screw isobutyronitrile (AIBN) breaks down (lower expression), ABCN into a cyanocyclohexyl radical to a cyanoisopropyl radical and lets you start a radical reaction.

 

Organic peroxide

The organic peroxide (peroxide) has -O-O- combination, and there disintegrates to an oxygen radical by heat. オキシルラジカル RO• It is は instability, and it is said that I cause the further resolution and turn into a more stable carbon radical. For example, tert-ブチルオキシルラジカル (t-BuO which the-tert-butyl peroxide (t-BuOOBu-t) and tert-butyl hydroperoxide (t-BuOOH) pyrolize it, and occurs•As for), radical methyl successively (CH₃•I disintegrate to) and acetone. Peroxidative benzoyl(BPO, PhC(=O)OOC(=O)Ph) ベンゾイルオキシルラジカル (PhC(=O)O•Disintegrate to), but is isolated with carbon dioxide successively; and a phenyl radical (Ph•I turn into). Provided methyl ethyl ketone peroxide is used as a start agent by methyl ethyl ketone.

Other

As the reagent that a radical is produced at low temperature, the combination of oxidizer and reducing agent including hydrogen peroxide and iron (II) salt, persulfate and the acid sodium sulfite is used. I call this a redox start agent.

Triethyl borane (Et₃B) and diethyl zinc (Et₂Zn) act at low temperature as a radical start agent, too.

Handling

Because the radical starts agent such as an azo compound or the organic peroxide is unstable, I am kept by a cool and dark space and a refrigerator. I am careful about the fear of the explosion and am handled.

Footnote

• Smith, M. B.; March, J. March's Advanced Organic Chemistry 6th ed. Wiley, 2007. Chapter 14.
• Nakajo good tree "high polymer chemistry" Maruzen, 1996. ISBN 4-621-04189-4

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