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

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Question 61

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In the addition of HBr to conjugated dienes, is the product which results from 1,2-addition or that which results from 1,4-addition typically the product of kinetic control?

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The product of kinet...

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Question 62

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In the planar conformation of 1,3-butadiene, the electron density in the π-system is ________ over the entire molecule.

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Question 63

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

Which diene reacts more rapidly in Diels-Alder reactions, cyclopentadiene or 1,3-butadiene? Briefly explain your choice.

Draw (Z)-1,3-hexadiene in its s-trans conformation.

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.

When (S) -3-bromopent-1-ene is heated in water, which of the following compounds is not produced?

When 1 mole of anhydrous HCl is reacted with excess 1,3-pentadiene, both the 1,2 and the 1,4-addition products are formed. Which of the following structures shown below is the least likely to be one of these products? (Note: When a chiral carbon is formed in this reaction a racemic mixture results, only one of the two possible enantiomers is shown.)

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 40°C.

Provide the major organic product of the following reaction.

Which of the following alkyl halides yields the most stable carbocation intermediate during solvolysis in hot ethanol?

What characterizes a pericyclic reaction?

Draw the LUMO of pentadienyl cation.

Indicate whether the following cyclization, conducted under thermal conditions, is symmetry allowed. Justify your answer by showing whether the overlapping orbitals in the transition state generate a symmetry-allowed or symmetry-forbidden scenario. Treat ethylene as the nucleophile.

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

What name is given to the type of "control" which arises in a reaction which does not achieve equilibrium and in which the product distribution is determined by the relative activation energies of the pathways which produced them?

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

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

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