on this site, we are unable to include diagrams, so I can only describe the structure.
Heptane is a linear chain of 7 Carbon atoms.
The designation "4-ethyl" means the ethyl subchain is attached to the 4th carbon atom.
The designation "2-mercapto" means that the SH (sulfur and hydrogen) are attached to the 2nd carbon.
Draw a chain of 7 carbon atoms, and attach the subchains in accord with their numbers.
