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A Chemist's Guide to Valence Bond Theory

Sason S. Shaik, Philippe C. Hiberty

Chapter 4

Mapping Molecular Orbital-Configuration Interaction to Valence Bond Wave Functions - all with Video Answers

Educators


Chapter Questions

02:25

Problem 1

Generate the 12 monoionic VB structures of the $\pi$-electronic system of butadiene.

Shazia Naz
Shazia Naz
Numerade Educator
04:50

Problem 2

Find the $6 \mathrm{VB}$ structures of the $\pi$-electronic system of ozone and write their wave functions. The overlaps between AO-based determinants can be neglected.

Vishal Sharma
Vishal Sharma
Numerade Educator
04:19

Problem 3

(a) Express the Hartree-Fock wave function of ozone in terms of the VB structures of the preceding exercise, given the list of the $\pi$ MOs below:
(TABLE CAN'T COPY)
(b) The $2 \times 2 \mathrm{CI}$ wave function of ozone reads
$$
\Psi_{2 \times 2}=0.908\left|\pi_1 \bar{\pi}_1 \pi_2 \bar{\pi}_2\right|-0.418\left|\pi_1 \bar{\pi}_1 \pi_3 \bar{\pi}_3\right|
$$
Express this wave function in terms of VB structures, and show that CI has the effect of increasing the weight of the diradical structure, and lowering those of the ionic structures, especially the 1,3-dipolar ones.
(c) Given the overlaps between the $\pi$ AOs of ozone below, calculate the weight of the diradical structure in the $2 \times 2 \mathrm{CI}$ wave function $\Psi_{2 \times 2}$, by means of the Chirgwin-Coulson formula (Eq. 3.55), taking all overlaps into account. We recall that, according to Equation 3.55, the weight of a VB structure can be calculated as the sum of the weights of its constituting AO-based determinants.
(TABLE CAN'T COPY)

David Collins
David Collins
Numerade Educator