$$\mathrm{3\text{-}Bromo\text{-}1\text{-}butene}$$

$$\mathrm{3\text{-}Bromocyclohexene}$$

$$\mathrm{1\text{-}Bromo\text{-}2\text{-}butene}$$

Question 1

Which of the following best explains why allylic carbocations are more stable than typical alkyl carbocations?

Accepted Answer

They are stabilized by resonance delocalization of the positive charge over multiple carbons.

Question 2

Which reagent is commonly used for selective allylic bromination of cyclohexene?

Accepted Answer

N-Bromosuccinimide (NBS)

Question 3

In the SN1 reaction of 3-chloro-3-methyl-1-butene with water, which factor most increases the rate compared to a non-allylic alkyl chloride?

Accepted Answer

Resonance stabilization of the allylic carbocation intermediate

Question 4

Which statement about conjugated dienes is correct?

Accepted Answer

Conjugated dienes have overlapping p orbitals that allow delocalization of electrons across all carbons involved.

Question 5

Which product is favored under kinetic control in the addition of HBr to 1,3-butadiene at -80°C?

Accepted Answer

$$\mathrm{3	ext{-}Bromo	ext{-}1	ext{-}butene}$$

Question 6

What is the major product when cyclohexene reacts with NBS in CCl$$_4$$?

Accepted Answer

$$\mathrm{3	ext{-}Bromocyclohexene}$$

Question 7

Which of the following best describes the molecular orbital interaction responsible for the Diels-Alder reaction?

Accepted Answer

The HOMO of the diene interacts with the LUMO of the dienophile.

Question 8

Which of the following is true about the stereospecificity of the Diels-Alder reaction?

Accepted Answer

The stereochemistry of the diene and dienophile is preserved in the product.

Question 9

Why are cumulated dienes (allenes) less stabilized by conjugation than conjugated dienes?

Accepted Answer

Their p orbitals are orthogonal and do not overlap for delocalization.

Question 10

Which rearrangement involves a [3,3]-sigmatropic shift and is important in biosynthetic pathways?

Accepted Answer

Cope rearrangement

Question 11

In the halogenation of propene with Cl$$_2$$ under UV light, what is the first propagation step?

Accepted Answer

A chlorine atom abstracts an allylic hydrogen to form an allylic radical.

Question 12

Which of the following is a correct IUPAC and common name for $$\mathrm{H_2C=$$CHCH_2$$}$$?

Accepted Answer

Allyl

Question 13

Which factor does NOT contribute to the stability of allylic carbocations?

Accepted Answer

Aromaticity

Question 14

Which product is favored under thermodynamic control in the addition of HBr to 1,3-butadiene at room temperature?

Accepted Answer

$$\mathrm{1	ext{-}Bromo	ext{-}2	ext{-}butene}$$

Question 15

Which of the following is a key requirement for a dienophile to react efficiently in a Diels-Alder reaction?

Accepted Answer

It should contain at least one electron-withdrawing group.

Question 16

Which of the following best describes the difference between 1,2- and 1,4-addition in reactions of conjugated dienes?

Accepted Answer

1,2-addition occurs at the adjacent carbons of the diene, while 1,4-addition occurs at the terminal carbons.

Question 17

Which statement about the endo vs exo orientation in the Diels-Alder reaction is correct?

Accepted Answer

The endo product is usually favored due to secondary orbital interactions.

Question 18

Which of the following is true about the Claisen rearrangement?

Accepted Answer

It is a [3,3]-sigmatropic rearrangement involving allyl vinyl ethers.

Question 19

Which of the following is NOT a property of conjugated dienes compared to isolated dienes?

Accepted Answer

Conjugated dienes have no delocalization of electrons.

Conjugation in Alkadienes and Allylic Systems: Structure, Reactivity, and Mechanisms

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