Question 1

Which of the following statements best describes the bonds broken and formed during a typical electrophilic addition reaction of an alkene, as shown in the first image?

Accepted Answer

A $$\pi$$ bond in the alkene and a $$\sigma$$ bond in the electrophile are broken; two new $$\sigma$$ bonds are formed in the product.

Question 2

Based on the enthalpy of hydrogenation data in the second image, which alkene is expected to be the most stable?

Accepted Answer

The tetrasubstituted alkene

Question 3

Which of the following best explains why more substituted alkenes are less reactive toward hydrogenation?

Accepted Answer

They are more stable due to hyperconjugation and alkyl group electron donation.

Question 4

In the hydrohalogenation mechanism (see image 3), what is the key intermediate formed after the alkene reacts with HCl?

Accepted Answer

A carbocation

Question 5

During acid-catalyzed hydration of an alkene, which product is favored according to Markovnikov's rule?

Accepted Answer

The alcohol forms on the more substituted carbon of the double bond.

Question 6

In oxymercuration-demercuration (see image 4), what is the role of the mercurinium ion intermediate?

Accepted Answer

It prevents carbocation rearrangement by stabilizing the positive charge.

Question 7

Which of the following statements about halohydrin formation (see image 5) is correct?

Accepted Answer

Water acts as the nucleophile, attacking the more substituted carbon of the bromonium ion.

Question 8

Which compound in image 6 is an internal alkyne?

Accepted Answer

$$\mathrm{CH_3C \equiv CCH_2CH_3}$$

Question 9

In the multistep synthesis shown in image 7, what is the effect of the order of steps on the stereochemistry of the final product?

Accepted Answer

Changing the order of steps can lead to different stereoisomers of the product.

Question 10

During acid-catalyzed tautomerization of an enol (see image 8), what is the final product when hydrating a terminal alkyne?

Accepted Answer

A ketone

Question 11

Which step in a radical halogenation mechanism (see image 9) is responsible for generating the first radical species?

Accepted Answer

Initiation

Question 12

Which mechanistic pattern (see image 10) is unique to radical reactions and not seen in polar mechanisms?

Accepted Answer

Homolytic cleavage

Question 13

In radical halogenation (see image 11), why is bromination more selective than chlorination?

Accepted Answer

Bromine radicals are less reactive and more selective for tertiary hydrogens.

Question 14

According to the roadmap (see image 12), which sequence would convert an alkene to a primary ether in two steps?

Accepted Answer

Alkene $$\rightarrow$$ alcohol $$\rightarrow$$ ether

Question 15

Which of the following is true regarding the stereochemistry of halogen addition to alkenes (as seen in image 4)?

Accepted Answer

Halogen addition proceeds via anti addition, leading to trans products.

Question 16

Which reagent would you use to selectively hydrogenate an alkyne to a cis-alkene?

Accepted Answer

Lindlar's catalyst

Question 17

Which of the following best describes the regioselectivity of hydroboration-oxidation of an alkene?

Accepted Answer

Anti-Markovnikov addition of water

Question 18

Which intermediate is NOT formed during the acid-catalyzed hydration of an alkene?

Accepted Answer

A halonium ion

Question 19

Which of the following is a correct statement about the product of ozonolysis of an internal alkyne?

Accepted Answer

It produces two carboxylic acids.

Addition, Mechanisms, and Reactivity of Alkenes and Alkynes: A Comprehensive Study Guide

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