Question 1

Which statement best explains why the addition of HBr to an alkene in the presence of peroxides leads to anti-Markovnikov product formation?

Accepted Answer

Peroxides generate free radicals, which initiate a radical chain mechanism that adds Br to the less substituted carbon.

Question 2

What is the major organic product when 1-methylcyclohexene reacts with HBr in the presence of ROOR (peroxide) and heat?

Accepted Answer

1-bromo-1-methylcyclohexane

Question 3

Which of the following best describes the stereochemistry of catalytic hydrogenation of alkenes?

Accepted Answer

Syn addition of hydrogen atoms across the double bond

Question 4

A solution of Br$$_2 in $$CCl$$_4 is $$added to an unknown compound. The red-brown color disappears rapidly. What does this indicate?

Accepted Answer

The compound contains a carbon-carbon double bond.

Question 5

Which reagent(s) would you use to convert 1-butene to 2-butanol with Markovnikov orientation and minimal carbocation rearrangement?

Accepted Answer

Hg(OAc)$$_2$$, H$$_2O$$; then NaBH$$_4$$

Question 6

Which of the following mechanisms involves a three-membered ring intermediate called a halonium ion?

Accepted Answer

Addition of halogens (e.g., Br$$_2) to $$alkenes

Question 7

What is the expected major product when cis-2-butene reacts with Br$$_2 in $$CCl$$_4 at $$room temperature?

Accepted Answer

A meso-2,3-dibromobutane

Question 8

Which statement correctly describes the orientation of addition in the hydration of alkenes using dilute H$$_2SO$_4$$?

Accepted Answer

The proton adds to the less substituted carbon, forming the more stable carbocation.

Question 9

Which of the following is true about the hydroboration-oxidation of alkenes?

Accepted Answer

It produces anti-Markovnikov alcohols via syn addition.

Question 10

A student treats cyclopentene with meta-chloroperoxybenzoic acid (MCPBA). What is the major product?

Accepted Answer

An equimolar mixture of enantiomeric epoxides

Question 11

Which of the following best explains why carbocation rearrangements can occur during the acid-catalyzed hydration of alkenes?

Accepted Answer

The reaction forms a carbocation intermediate, which can rearrange to a more stable carbocation via methyl or hydride shift.

Question 12

Which of the following reagents would convert an alkene to a syn-1,2-diol?

Accepted Answer

OsO$$_4$$ followed by H$$_2O$_2$$

Question 13

What is the function of the peroxide (ROOR) in the free-radical addition of HBr to alkenes?

Accepted Answer

It acts as a radical chain initiator.

Question 14

Which of the following best describes the product of ozonolysis of 1-methylcyclohexene followed by reduction with Zn?

Accepted Answer

An aldehyde and a ketone

Question 15

Which of the following statements about the addition of halogens to alkenes is correct?

Accepted Answer

The addition is anti and forms a vicinal dihalide.

Question 16

Which of the following is a key difference between oxymercuration-demercuration and acid-catalyzed hydration of alkenes?

Accepted Answer

Oxymercuration-demercuration does not allow carbocation rearrangement, while acid-catalyzed hydration does.

Question 17

Which of the following best describes the product formed when an alkene reacts with Br$$_2 in $$water?

Accepted Answer

A bromohydrin, with Br and OH on adjacent carbons

Question 18

Which of the following reagents would you use to convert an alkene to an ether via Markovnikov addition?

Accepted Answer

Hg(OAc)$$_2$$, ROH; then NaBH$$_4$$

Question 19

Which of the following is true about the stereochemistry of carbene addition to alkenes?

Accepted Answer

The cyclopropane product retains the cis or trans stereochemistry of the original alkene.

Question 20

Which of the following best describes the product of the reaction of an alkene with OsO$$_4$$ followed by H$$_2O$_2$$?

Accepted Answer

A syn-1,2-diol

Chapter 8: Reactions of Alkenes – Mechanisms, Stereochemistry, and Applications

Guida di studio - Domande di pratica