1,1 -Azobis-1-cyclohexanenitrile

This reagent is useful for initiating radical reactions. Since it is a radical initiator, only small amounts are needed. For reactions at higher temperature, ACN (1,1 -azobis-1 -cyclohexanenitrile [2094-98-6]) has been suggested (see Example 2).1... 

The first step in our procedure for initiating the free-radical chain reaction is the homolysis of l,r-azobis[cyclohexanenitrile] (1), abbreviated as ABCN, to form nitrogen and the free radical 2 (Eq. 9.5). The rate of this reaction is sufficiently fast at 80-100 °C to generate enough chlorine atoms to initiate the chain process. The radical 2 then attacks sulfuryl chloride to generate chlorine atoms and SO2 according to Equations 9.6 and 9.7. The series of reactions depicted in Equations 9.S-9.7 comprise the initiation steps of the reaction. 

The traditional method of oxidizing hydrazine derivatives makes use of halogens or hypohalites as oxidizing agents. The techniques range from the preparation of l,l -azobis(l-cyclohexanenitrile) by the addition of bromine to an alcoholic hydrochloric acid solution of the corresponding hydrazine [89], through the use of bromine water [90, 91] to oxidations with sodium hypo-bromite [64] or sodium hypochlorite [92]. 

For certain types of radical reaction, AIBN may not always give optimal results. Keck and Burnett found in their synthesis of PGp2a that the introduction of the lower side chain, involving radical addition onto a B-stannyl enone, was inefficient when AIBN was used as initiator at 65 °C. By conducting the reaction in refluxing toluene (110°C), and replacing AIBN with the related IJ -Azobis-l-cyclohexanenitrile (ACN), a markedly better yield of the desired adduct was obtained (eq 10). ... 

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