Which of the following is correct?

Options

A. Cyclopentadieneis much more acidic that 1,3-cyclohexadiene.
B. An H of the `CH_(2)` group in cycloheptatriene is much less acidic than a typical allylic H.
C. Tropylium bromide (7-bromocycloheptatriene) completely dissociates in water and gives a precipitate of AgBr instantaneously with `AgNO_(3)`, unlike its open chain analog, 3-bromo-1,4-pentadiene.
D. All of these

Answer

4

Explanation

The removal of the hydrogen atom as `H^(+)` from saturated C of cyclopentadiene, converts it to an `sp^(2)` hybridized C with a pair of `e^(-)`'s in a p atomic orbital that overlaps with the p atomic orbitals on both sides, giving rise to a ringwith six (a Huckel number) delocalized `pie^(-)`'s. This aromaticity stabilizes the cyclopentadienyl anion causing cyclopentadiene to be much more acidic than most Hydrocarbons. On the other hand, the removal of the hydrogen from cyclohexa-1,3-diene, also gives an anion with atoms as `H^(+)` ion six `e^(-)` in the ring but the presence of an `sp^(3)` C prevents contivuous cyclic overlap and the anion is not aromatic The removal of an `H^(+)` from the `CH_(2)` group in cycloheptatriene leads to the cyclohepatrienyl carbanion with `8 pie^(-)`'s which is not a Huckel number. The cycloheptatrienyl carbocation formed by a loss of `H^(-)` is usually stable. It has an empty p atomic orbital being `sp^(2)` hybridized. it is aromatic, having six `pie^(-)`'s delocalized in seven overlapping p orbitals.