For the given reaction,the total number of possible products formed by the tertiary carbocation of $A$ is $.........$.

Classify the following species into carbocation,free radical,and carbanion:
$CH_3^{\bullet}, CH_3^{+}, \bar{C}H_3, (CH_3)_3C^{\bullet}, (CH_3)_3C^{+}, (CH_3)_2CH^{+}, (CH_3)_3\bar{C}:, (CH_3)_3\ddot{C}H, C_6H_5CH_2^{\bullet}, CH_3\ddot{C}H_2, C_6H_5CH_2^{+}, CH_2=CHCH_2^{\bullet}, CH_2=CHCH_2^{+}$

In the above reaction,the left-hand side and right-hand side rings are named as '$A$' and '$B$' respectively. They undergo ring expansion. The correct statement for this process is:

Which of the following is the most stable carbocation?

Rank the transition states that occur during the following reaction steps in order of increasing stability (least $\to$ most stable):
$1.$ $CH_3-O^+H_2 \to CH_3^+ + H_2O$
$2.$ $(CH_3)_3C-O^+H_2 \to (CH_3)_3C^+ + H_2O$
$3.$ $(CH_3)_2CH-O^+H_2 \to (CH_3)_2CH^+ + H_2O$

The central carbon atom of a free radical contains