Preparation from Alkyl Fluorides in Antimony Pentafluoride Solution

Propyl, butyl, and pentyl fluorides with antimony pentafluoride gave the isopropyl, t-butyl and t-amyl cations (as their fluoroantimonate salts) 2,1 and 3. 

The secondary butyl and amyl cations can be observed only at very low temperatures and they rearrange readily to the more stable tertiary ions. 

Generally, the most stable tertiary or secondary carbocations are observed from any of the isomeric alkyl fluorides in superacidic solvent system. 

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