Question 1

Which statement best describes the role of the pi bond in electrophilic addition reactions of alkenes?

Accepted Answer

The pi bond acts as a nucleophile, attacking electrophilic species.

Question 2

According to Markovnikov’s rule, when HBr is added to 2-methylpropene, where does the bromine atom attach?

Accepted Answer

To the carbon with the fewer number of hydrogens.

Question 3

What is the rate-determining step in the electrophilic addition of HX to an alkene?

Accepted Answer

Protonation of the double bond to form a carbocation.

Question 4

Why does the addition of HBr to an alkene in the presence of peroxides result in anti-Markovnikov products?

Accepted Answer

Peroxides produce free radicals, which favor addition to the less substituted carbon.

Question 5

Which reagent is used for oxymercuration-demercuration of alkenes, and what is the stereochemical outcome?

Accepted Answer

Hg(OAc)2 followed by NaBH4; Markovnikov addition without rearrangement.

Question 6

In hydroboration-oxidation of alkenes, what is the orientation and stereochemistry of the product?

Accepted Answer

Anti-Markovnikov orientation, syn addition.

Question 7

Which of the following best explains why only HBr, and not HCl or HI, undergoes anti-Markovnikov addition in the presence of peroxides?

Accepted Answer

The reaction of alkyl radicals with HCl or HI is strongly endothermic.

Question 8

What is the intermediate formed during the addition of Cl2 or Br2 to an alkene?

Accepted Answer

Halonium ion

Question 9

When an alkene reacts with Br2 in water, what is the major product and its stereochemistry?

Accepted Answer

Bromohydrin, anti addition

Question 10

Which catalyst is used in catalytic hydrogenation of alkenes, and what is the stereochemical outcome?

Accepted Answer

Pt, Pd, or Ni; syn addition of hydrogen

Question 11

What is the product when cyclohexene is treated with CH2I2 and Zn(Cu)?

Accepted Answer

Cyclopropane ring fused to cyclohexane

Question 12

Which reagent is most commonly used for epoxidation of alkenes?

Accepted Answer

Meta-chloroperoxybenzoic acid (MCPBA)

Question 13

What is the outcome when an alkene is treated with OsO4 followed by H2O2?

Accepted Answer

Syn-1,2-diol

Question 14

What products are formed when an alkene undergoes ozonolysis followed by reduction with dimethyl sulfide?

Accepted Answer

Aldehydes and ketones

Question 15

Which of the following is a termination step in cationic polymerization of alkenes?

Accepted Answer

Abstraction of a proton to form an alkene

Question 16

What is the key requirement for an alkene to undergo anionic polymerization?

Accepted Answer

Presence of strong electron-withdrawing groups on the double bond

Question 17

Which process involves the exchange of alkylidene groups between alkenes using a metal catalyst?

Accepted Answer

Olefin metathesis

Question 18

A patient receives a polyethylene knee implant. Which polymerization method is most likely used to produce polyethylene?

Accepted Answer

Free-radical polymerization

Question 19

Which of the following best describes the stereochemical outcome of halogen addition to a cis-alkene?

Accepted Answer

The product is a trans dihalide due to anti addition.

ch 8 Reactions of Alkenes: Mechanisms, Stereochemistry, and Applications

Study Guide - Practice Questions