Initiation, of radical reactions

C, decomposes slowly into cyanopropyl radicals and is useful for initiation of radical reactions. 

Initiation of radical reactions with uv radiation is widely used in industrial processes (85). In contrast to high energy radiation processes where the energy of the radiation alone is sufficient to initiate reactions, initiation by uv irradiation usually requires the presence of a photoinitiator, ie, a chemical compound or compounds that generate initiating radicals when subjected to uv radiation. There are two types of photoinitiator systems those that produce initiator radicals by intermolecular hydrogen abstraction and those that produce initiator radicals by photocleavage (86—91). 

The use of metal-complex initiating systems proved to be especially promising in carrying out the reactions with acrylic monomers which can be easily polymerized, when the common initiators of radical reactions are excepted. The use of Fe(CO)s -I- DMFA system allows us to perform homolytical addition of bromoform to acrylic monomers selectively at C-Br bond with no essential polymerization (ref. 10). 

Dibenzoyl peroxide is an important compound because it can act as another initiator of radical reactions we ll see why later. It undergoes homolysis simply on heating. 

Puriflcation is effected by recrystallization from methanol and drying in vacuum over phosphorus pentoxide. Under mild conditions (4(F) the reagent decomposes into cyanopropyl radicals and hence is useful for initiation of radical reactions. ... 

Photochemically or thermally induced elimination of nitrogen from aliphatic azo compounds (see also Section 6.4.1) is accompanied by the formation of alkyl radicals [Dc t (azoethane) = 209kJmol 1].874 For example, photodecomposition of 2,2 -azobisi-sobutyronitrile (A1BN), a well-known thermally activatable initiator of radical reactions, produces cyanodimethylmethyl radicals (Scheme 6.166). Similar reactions have... 

Beilstein Handbook Reference) Borane, triethyl- Boron ethyl Boron triethyl BRN 1731462 EINECS 202-620-9 HSDB 897 Triethylborane Triethylborine Triethylboron. Used as an initiator of radical reactions. Liquid mp = -93° bp = 95° d = 0.700 ... 

The behavior of 1 -adamantyl radical in chlorine atom abstraction has been investigated recently [18f]. Initiators of radical reactions and some metal complexes induce dark chlorination of saturated hydrocarbons with Cl2or CCU[19]. 

Aliphatic azo compounds are also important, most notably as initiators of radical reactions, including radical polymerizations. The most common reagent used for this purpose is azobisisobutyronitrile (AIBN), which decomposes on gentle heating to N2 and a pair of 2-cyanoprop-2-yl radicals ... 

The easy oxidation of thiols on exposure to air is well known as is the sensitivity of this reaction to catalysts like metal ions, u.v. light and other initiators of radical reactions. It is also known that autooxidation of thiols is accelerated by bases. 

The most important application of organostannanes is the initiation of radical reactions with -Bu3Sn-H, such as the replacement of halide (X) by H shown below ... 

ON THE MECHANISM OE INITIATION OF RADICAL REACTIONS BY NITROGEN DIOXIDE DIMERS... 

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