Question 1

What descriptive term is applied to the type of diene shown in the structure above?

Accepted Answer

An isolated diene

Question 2

Which of the following compounds has the smallest heat of hydrogenation, indicating the greatest stability?

Accepted Answer

(E)-2-methyl-2,4-hexadiene

Question 3

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

Accepted Answer

1,2-pentadiene \u003c 1,4-pentadiene \u003c cis-1,3-pentadiene \u003c trans-1,3-pentadiene

Question 4

Among a series of isomeric trienes, the more negative the $$\Delta H^\circ of $$the hydrogenation reaction of a given triene, the ________ stable it is relative to the others in the isomeric series.

Accepted Answer

less

Question 5

Which of the following compounds is the most stable?

Accepted Answer

(E)-2-methyl-1,3-pentadiene

Question 6

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

Accepted Answer

the s-trans conformer is lower in energy than the s-cis

Question 7

What is the resonance energy of a system?

Accepted Answer

The energy difference between the actual molecule and the most stable hypothetical non-resonance structure

Question 8

Which substrate would react most rapidly in an $$\mathrm{S_N2}$$ reaction?

Accepted Answer

$$\mathrm{CH_3CH_2CH=CHCH_2Br}$$

Question 9

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

Accepted Answer

pent-4-en-1-ol

Question 10

In the diene shown in the image, what is the relationship between the two double bonds?

Accepted Answer

They are isolated

Question 11

Which of the following best explains why the double bond labeled 'A' in a diene reacts preferentially with HBr to give the major product?

Accepted Answer

The resonance structures formed upon addition of HBr to double bond A lead to a more stable carbocation intermediate.

Organic Chemistry: Dienes, Resonance, and Reaction Mechanisms Study Guide

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