Number of benzene derivatives of $C_7H_7Cl$ is :

Which of the following compounds is planar in shape?

Benzene is treated with oleum to produce compound $(X)$,which when further heated with molten sodium hydroxide followed by acidification produces compound $(Y)$. The compound $(Y)$ is treated with zinc metal to produce compound $(Z)$. Identify the structure of compound $(Z)$ from the following options.

The electrophile $NO_2^+$ reacts with which of the following compounds? In which case will $NO_2^+$ attack at the meta position?
$(I)$ $C_6H_5-CCl_3$
$(II)$ $C_6H_5-NO_2$
$(III)$ $C_6H_5-CHO$
$(IV)$ $C_6H_5-O^-$

Which of the following is not a $m-$directing group?

In the nitration of benzene,concentrated $HNO_3$ acts as a: