When 1,3,5-cycloheptatriene is treated with the powerful hydride (h-) acceptor triphenylmethyl fluoroborate, a light yellow water-sensitive salt a, c7h7bf4, is formed. draw the structure of a?

Triphenylmethyl fluoroborate is a powerful hydride accept because it has a trisubstituted tertiary carbocation. This carbocation is quite stable on its own, however, it is a great electron acceptor which will stabilize the molecule completely. Meanwhile, 1,3,5-cycloheptatriene is a triene with a seven membered ring. While this molecule can be stable on its own, it has a tendency to want to become aromatic, as aromatic compounds are very stable due to the resonance and conjugation within a ring. By abstracting a hydride from this cycloheptatriene, we form a carbocation called the tropylium ion. It turns out that this carbocation has 6 pi electrons and is cyclic, which makes this structure an aromatic ring. The mechanism of the reaction is shown in the attached image and the carbocation is shown as a single resonance structure and as the overall aromatic structure. The fluoroborate anion becomes the counterion for the new aromatic cation.