Exam 15: Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy

Including all possible stereoisomeric forms, how many distinct allylic bromides could be produced when 2-methylpent-1-ene is treated with NBS under irradiation by a sunlamp?

Which of the following terms best describes a Diels-Alder reaction?

Draw the HOMO of 1,3-butadiene.

Which has a l_max in its UV spectrum at a longer wavelength, 2,4-hexadiene, 1,4-hexadiene, or 1,5-hexadiene?

Predict the major product of the following reaction:

Provide the structure of the major organic product in the following reaction.

Draw the structure of the major product which results when the diene shown is treated with HBr at -80°C.

Provide the structure of the major organic product in the following reaction.

Provide the structure of the major organic product in the following reaction.

Provide the structure of the major organic product in the following reaction.

When 1-methylcyclohex-2-en-1-ol is treated with HBr, two constitutionally isomeric bromides are produced. Provide a detailed, stepwise mechanism which explains this observation.

Which of the following compounds is the most stable?

Give a representation of the highest occupied π MO of 1,3-butadiene in its ground state.

The following [3+2] cycloaddition was reported in Organic Letters, 2011, 402. Predict whether the reaction would be thermally or photochemically promoted. Justify your answer by showing overlap of the correct molecular orbitals. Assume the alkene is the electrophile.

What diene and dienophile are used in the Diels-Alder route to the compound shown?

When the relative energies of the s-cis and s-trans conformers of 1,3-butadiene are compared, one finds that:

The Diels-Alder reaction is a concerted reaction; this means :

In the UV-visible spectrum of (E)-1,3,5-hexatriene, the lowest energy absorption corresponds to a:

Provide the structure of the major organic product in the following reaction.

Show how the carbon p orbitals overlap to form the LUMO of the allyl anion.