The $IUPAC$ name of the compound $CH_3-CH_2-CH(CH_3)-CH_2-COCl$ is:

The structural formula of $2$-methyl-$2$-butene is

The $IUPAC$ name of the structure is:

Fill in the blanks:
$(1)$ The $IUPAC$ names of $CH_3COOCH_3$ and $CH_3CH_2COOCH_3$ are ....... and ....... respectively.
$(2)$ ....... isomers of dibromobenzene exist.
$(3)$ ........ is the $IUPAC$ name and ........... is the common name of $C_6H_5OCH_3$ respectively.
$(4)$ The structure of $1-$chloro$-2,4-$dinitrobenzene is shown below.

The $IUPAC$ name of the given compound is:

What is the $IUPAC$ name of the given compound?