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

Provide a picture of the LUMO of 1,3,5-hexatriene.

Provide the major organic product of the following reaction.

In the diene shown below, there are two possible double bonds that could react when 1 eq. of HBr is added. However, the double bond labeled "A" reacts preferentially to give the major product. Using resonance structures, justify this observation.

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

What diene and dienophile would react to give the product below?

Explain why S_N2 reactions on allyl bromide proceed faster than corresponding reactions on ethyl bromide.

Draw the LUMO of pentadienyl anion.

Give a representation of the antibonding π molecular orbital of the allyl cation.

What is the hybridization of the central carbon of allene (1,2-propadiene)?

Give a representation of the bonding π molecular orbital of the allyl anion.

Provide the two major organic products of the following reaction.

Among a series of isomeric trienes, the more negative the ΔH° of the hydrogenation reaction of a given triene, the ________ stable it is relative to the others in the isomeric series.

Name the two major products which are formed when undergoes solvolysis in hot methanol.

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

Rank the following dienes in order of increasing stability: trans-1,3-pentadiene, cis-1,3-pentadiene, 1,4-pentadiene, and 1,2-pentadiene.

Predict the major product of the following reaction:

The following Diels-Alder reaction was featured in Tet. Lett. 2011, 960. Predict the structure of the starting materials.

Given that 1,3-butadiene has a uv absorption of 217nm, predict the approximate absorption for the conjugated system in vitamin D₃.

Provide the structure of the major product which results from 1,2-addition of HBr to the diene shown below.

What diene and dienophile would react to give the product below?