In the first step of the mechanism of alkene hydrobromination, which of the following orbitals is the LUMO?

Which of the following molecules would you expect to absorb in the visible region of the electromagnetic spectrum?

(e)

Would you expect the following molecules to absorb in the UV–visible region of the electromagnetic spectrum?

(a)

(b)

(c)

(d)

(e)

Consider the Molecular Orbitals (MO’s) of the allyl anion. Which are the HOMO and LUMO?

Identify the HOMO and LUMO of the allylic cation and the allylic anion shown in Figure 21.22.

<IMAGE>

Draw the molecular orbital picture for (a) ethene. Label the HOMO and LUMO of each.

Predict the λ_max of the following compound:

Match four of the following UV absorption maxima (λ_max) with the corresponding compounds: (1) 232 nm; (2) 256 nm; (3) 273 nm; (4) 292 nm; (5) 313 nm; (6) 353 nm.