Electrophilic attack General Subject

The mechanism for the polymerization probably fits the general pattern of electrophilic attack by the initiator on the carbonyl oxygen atom for the initiation step, with propagation taking place by attack of the electron deficient C-4 of the last unit of the growing chain on the carbonyl group of a monomer molecule. Certain modifications of this general mechanism are apparently observed with specific catalysts, and the subject appears to need further study. 

In this chapter, we have seen that an acetylide ion can function as a nucleophile and attack an alkyl halide in an n2 process. More generally speaking, the acetylide ion can attack other electrophiles as well. For example, we will see in Chapter 14 that epoxides function as electrophiles and are subject to attack by a nucleophile. Consider the following reaction between an acetylide ion (the nucleophile) and an epoxide (the electrophile) ... 

Nafion , a perfluoroalkyl polymer resin containing sulfonic acid groups, has been compared with trifluoromethanesulfonic acid for its regioselectivity in the labeling of model quinolines, pyridines, anilines, toluene and chlorobenzene the reaction mixtures contained substrate, resin and a small volume of tritiated water. Reactions were conducted at 90-180 °C for up to several days and gave product specific activities only a fraction of those of the tritiated water batches. Generally, both catalysts label positions subject to electrophilic attack, but Nafion behaved as a weaker acid than its homogeneous counterpart. 

There have been only a few reports of direct hydroxylation362 by an electrophilic process (see, however, 2-26 and 4-5).363 In general, poor results are obtained, partly because the introduction of an OH group activates the ring to further attack. Quinone formation is common. However, alkyl-substituted benzenes such as mesitylene or durene can be hy-droxylated in good yield with trifluoroperacetic acid and boron trifluoride.364 In the case of mesitylene, the product is not subject to further attack ... 

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