Carboxonium ions hydride abstraction

As discussed in Chapter 1, Brouwer and Kiffen reported the observation that HF-BF3 promoted hydride transfer from isoalkanes to acyl cations. These results were later shown by Olah and co-workers to be due to superelectrophilic activation of the acyl cation (24, eq 13).37 Diproto-nated acetone and aldehydes were also shown to abstract hydride from isoalkanes in HF-BF3 solutions.38 Carboxonium ions (25) are generally... 

Cycloheptatriene (C7H8) is detected readily by GLC, but as before the fate of the cyclic carboxonium ion remains enigmatic. Nevertheless, polymerization of THF proceeds smoothly and reproducibly especially at temperatures above 50 °C. Other workers (36) have used triphenyl-methyl salts to polymerize trioxane, and the general conclusion remains that hydride abstraction is a primary initiation process, although in all cases there is no clear evidence for the fate of carboxonium ion formed. 

The carboxonium ions may participate in chain transfer through hydride abstraction reaction ... 

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