Question 1

Which statement best explains why addition reactions to alkenes are thermodynamically favored, despite not being favored by entropy?

Accepted Answer

Addition reactions increase the number of sigma bonds, which are more stable than pi bonds.

Question 2

In the reaction $$\mathrm{H_2C=CH_2$ + HBr \rightarrow H_3C-CH_2Br}$$, what is the enthalpy change ($$\Delta H) $$and what does it indicate about the reaction?

Accepted Answer

$$\Delta H = -19$$ kcal/mol; the reaction is exothermic and thermodynamically favored.

Question 3

Which of the following statements is a kinetic statement?

Accepted Answer

Compound A is more reactive than compound C.

Question 4

Markovnikov's rule states that in the addition of HX to an alkene, the hydrogen atom attaches to the carbon with:

Accepted Answer

The greatest number of hydrogen atoms already present.

Question 5

Which factor most stabilizes a carbocation intermediate during electrophilic addition to an aromatic ring?

Accepted Answer

Resonance with neighboring pi bonds.

Question 6

The Finkelstein reaction is used to convert alkyl chlorides to alkyl iodides. What drives the equilibrium toward the iodide product?

Accepted Answer

Limited solubility of NaCl in acetone.

Question 7

Why does acid-catalyzed hydration of alkenes often produce a racemic mixture of alcohols?

Accepted Answer

The reaction proceeds through a planar carbocation intermediate, allowing attack from either side.

Question 8

Which reagent combination prevents carbocation rearrangement during alkene hydration?

Accepted Answer

a) $$\mathrm{Hg(OAc)_2}$$, b) $$\mathrm{$$NaBH_4$$}$$

Question 9

Which statement about Lewis acids is correct?

Accepted Answer

A Lewis acid binds to a lone pair of electrons.

Question 10

What is the main advantage of oxymercuration-demercuration over acid-catalyzed hydration of alkenes?

Accepted Answer

No carbocation rearrangement occurs, leading to predictable Markovnikov addition.

Question 11

Which boron reagent is commonly used for hydroboration of alkenes?

Accepted Answer

$$\mathrm{BH_3$} ($$borane)

Question 12

Hydroboration-oxidation of alkenes produces which type of alcohol?

Accepted Answer

Anti-Markovnikov alcohol with syn addition.

Question 13

During hydroboration-oxidation, what is the stereochemical outcome of the addition?

Accepted Answer

Syn addition: both boron and hydrogen add to the same face of the alkene.

Question 14

Which reagent is used for syn-dihydroxylation of alkenes to form glycols?

Accepted Answer

$$\mathrm{$$OsO_4$$} ($$osmium tetroxide)

Question 15

What is the role of sodium borohydride ($$\mathrm{$$NaBH_4$$}) in $$oxymercuration-demercuration?

Accepted Answer

It reduces and removes mercury from the organic product.

Question 16

Which intermediate is formed during the bromination of alkenes?

Accepted Answer

Bromonium ion

Question 17

What is the stereochemical outcome of bromination of alkenes?

Accepted Answer

Anti addition: bromine atoms add to opposite faces of the double bond.

Question 18

Which reagent is commonly used for anti-dihydroxylation of alkenes?

Accepted Answer

$$\mathrm{MCPBA}$$ followed by acid or base-catalyzed hydrolysis

Question 19

Ozonolysis of alkenes produces which types of products?

Accepted Answer

Aldehydes and ketones

Advanced Reactions of Alkenes: Mechanisms, Regiochemistry, and Stereochemistry

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