Competetive reactions

A polymerization process can be considered as a reaction system with consecutive and competetive reactions (see section 3.4). The "selectivity" problem is quite complica. But one can see at a first glance, that by influencing the relative rates of initiation or propagation (consecutive reactions), and of termination or chain transfer (competetive reactions), not only the average degree of polymerization will be influenced, but also its distribution. This results in a certain molecular mass distribution in the end product. 

For an effective control of the degree of polymerization, the terminating agent should react relatively slowly. Occasionsdly, termination occurs through a competetive reaction of one of the end groups which renders it inactive, e.g., a decomposition or a disproportionation (e.g., of polyester end groups). 

In contrast to most reported electrophilic reactions of CF2=CFCF3, addition of CF3OCl to this olefin is not regiospecific, and it results in formation of two isomers [9], which maybe an indication that a competetive radical pathway also operates in this reaction ... 

Reactions of organic anions. Part L VIII. The problem of competetive nucleophilic substitution of ortho- and para-halogens in 2,4-dihalonitrobenzenes by some carbanions. M. Makosza, J. M. Jagusztyn-Grochowska and M. Jawdosiuk, Rocz. Chem. 50y 1841 (1976)... 

Figure 4.14 Competetive tritiolysis reactions in the Pd-catalyzed tritiations of olefinic...

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