Carbocations, continued rearrangement

Formed carbocations can undergo p scission [Eq. (2.8)] to yield propylene (or the corresponding alkene, but not ethylene) and a new primary cation. The primary ion rapidly rearranges to a secondary ion involving a hydride shift [Eq. (2.9)], which, in turn, can continue the process. Isomeric cations may also be formed through intermediate alkenes [Eq. (2.10)] ... 

Carboanionic Intermediates.—Whereas characterization of the carbocations active in cationic polymerization has been difficult, identification and quantification of the carboanionic centres in anionic propagations have been somewhat easier, largely as a result of a considerably reduced tendency to rearrange and isomerize. Nevertheless, detailed investigations continue in particular areas. Thus Bywater and Worsfold ° have used n.m.r. spectroscopy to probe the structure of various model compounds which closely resemble those presumed to be responsible for anionic propagations. Whereas in tetrahydrofuran solvent 2,5-diphenyl-2,5-dipotassiohexane and 2-lithio-4,4-dimethyl-2-phenyl-pentane display coupling constants consistent with the carbon atoms... 

---