Write the structure of the compound: 1-chloro-4-ethylcyclohexane.
 

What is $\mathrm{A}$in the following reaction?
 

Arrange the following compounds in the increasing order of their boiling points: 

Chloromethane, Chloroform, Iodomethane, Bromomethane

Write a chemical reaction in which an iodide ion displaces the diazonium group from diazonium salt.

In the following pairs of halogen compounds, which compound undergoes ${\mathrm{S}}_{\mathrm{N}}2$ reaction faster?

 and.