Answer
For the skeletal structure of quetiapine (see picture for solution), you just need to drop the H-atoms and hide the C-atoms. Keep in mind, to draw the other atoms, namely nitrogen, oxygen as well as sulfur. Otherwise you won't know, that atoms other than hydrogen belong to this structure.
Molecular formula: $C_{21}H_{25}N_{3}O_{3}S$
Work Step by Step
Regarding rings and carbon chains, carbons and hydrogen atoms aren't explicitly shown. Instead, a carbon chain consists of a zig zag line while for a ring, the carbons are hidden and hydrogens attached to them are dropped. Other atoms are included into the skeletal structure.
- the molecular formula contains the actual number of atoms in a molecule.
- So, in order to get the molecular formula for quetiapine, you simply count the number of occurrences of each type of atom and write it as a subscript next to that atom. If an atom just appears once in this substance then you just mention this atom in the molecular formula, i.e. just note down the symbol of this atom.
