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

Dicylopentadiene results when cyclopentadiene reacts with itself in a Diels-Alder reaction. Provide the structure of dicyclopentadiene. Pay particular attention to stereochemical detail.

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

How many nodes, other than the node coincident with the molecular plane, are present in the LUMO of 1,3,5-hexatriene?

Assuming kinetic conditions, draw the major product of the reaction below. Include correct stereochemistry.

What characterizes a pericyclic reaction?

Which of the following compounds is the most reactive dienophile in a Diels-Alder reaction with 1,3-butadiene?

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

What is the major organic product which results when cycloheptene is irradiated in the presence of N-bromosuccinimide?

For what does the acronym HOMO stand?

Using resonance structures, explain the regiochemistry observed in this reaction:

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

When 3-bromo-1-methylcyclohexene is heated in a good ionizing solvent, reactions occur through a carbocation intermediate. Draw all reasonable resonance contributors of this cation and indicate which is the major contributor.

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

Draw the major organic product that results from the intramolecular Diels-Alder reaction.

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

Which sequence correctly ranks the following conjugated systems in order of increasing UV λ_max absorption values?

Draw the most stable conformation of (2Z,4E)-2,4-hexadiene.

What descriptive term is applied to the type of diene represented by 1,5-octadiene?

How many nodes, other than the node coincident with the molecular plane, are present in the HOMO of 1,3,5-hexatriene?

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.