Group 3: Pyrrole derivatives
Student Names:
The chemical formula of pyrrole is C4H5N. It is a cyclic conjugated molecule composed of 4
carbon atoms (sp2 hybridized) and one nitrogen atom.
N
H
Build the molecule with ZOA and clean the structure (see the word document and the power
point presentation on Zoa). Check that you have the correct number of hydrogen atoms.
Compute a MOPAC calculation (single point) for that structure (XXXX). Visualize the
molecular orbitals with ZOA and read their energies.
1) Report on an energy axis (in eV) all -occupied and -unoccupied electronic levels.
2) For each level, draw the shape of the molecular orbital. Indicate if some molecular
orbitals are degenerate.
3) How many -electrons has the molecule? Find the HOMO and LUMO level of the
molecule.
4) Replace one hydrogen atom (attached to the carbon indicated with an arrow) with one
iodine atom I. How does the HOMO and LUMO change in shape and energy.
5) Replace one hydrogen atom (attached to the carbon indicated with an arrow) with an
arrow with one methoxy group “–O-CH3”. How does the HOMO and LUMO change
in shape and energy.
6) Replace one hydrogen atom (attached to the carbon indicated with an arrow) with one
fluorine atom F. How does the HOMO and LUMO change in shape and energy.
7) Replace one hydrogen atom (attached to the carbon indicated with an arrow) with one
nitrile group “-CN”. How does the HOMO and LUMO change in shape and energy.
8) What is the relation between the energy change in the HOMO and LUMO by
replacing H by F or I, and the electronegativity of the H, F and I atoms?
9) According to that observation determine if the methoxy group has an electron donor
character or an electron acceptor character. What about the nitrile group, does it has an
electron donor or acceptor character?