Question 1

Which statement best describes the role of the π bond in the reactivity of alkenes?

Accepted Answer

The π bond increases the electron density above and below the plane of the molecule, making alkenes susceptible to electrophilic attack.

Question 2

In the electrophilic addition of HBr to 2-methyl-2-butene, which carbon does the Br atom attach to according to Markovnikov's rule?

Accepted Answer

The carbon with the fewest hydrogen atoms attached.

Question 3

Which of the following best explains why tertiary carbocations are more stable than secondary or primary carbocations?

Accepted Answer

Alkyl groups donate electron density through hyperconjugation and inductive effects, dispersing the positive charge.

Question 4

Consider the reaction: $$CH_3CH=CH_2$ + HBr \rightarrow$$ major product. What is the major product?

Accepted Answer

$$CH_3CHBrCH_3$$

Question 5

Which step in the electrophilic addition of HBr to an alkene is rate-determining?

Accepted Answer

Formation of the carbocation intermediate.

Question 6

A 1,2-hydride shift occurs during the addition of HBr to certain alkenes. What is the purpose of this shift?

Accepted Answer

To convert a less stable carbocation into a more stable one.

Question 7

Which of the following reactions will NOT result in a carbocation rearrangement?

Accepted Answer

Hydroboration-oxidation of an alkene.

Question 8

What is the major product when cyclohexene reacts with $$Br_2 in$$ $$CH_2Cl_2$$?

Accepted Answer

trans-1,2-dibromocyclohexane

Question 9

Which reagent is used to convert an alkene into a vicinal diol via syn addition?

Accepted Answer

$$OsO_4$$ followed by $$KHSO_3$$

Question 10

Which of the following best describes the product of hydroboration-oxidation of 1-butene?

Accepted Answer

1-butanol, with OH added to the less substituted carbon

Question 11

Which statement about Markovnikov’s rule is correct?

Accepted Answer

The hydrogen atom adds to the sp$$^2$$ carbon with the most hydrogens already attached.

Question 12

Which of the following is the correct order of carbocation stability?

Accepted Answer

tertiary \u003e secondary \u003e primary \u003e methyl

Question 13

What is the product of the reaction: $$CH_3CH_2C\equiv CH + NH_2$^- \rightarrow$$ ?

Accepted Answer

$$CH_3CH_2C\equiv C^- ($$acetylide ion)

Question 14

Which catalyst is used for the syn hydrogenation of alkynes to cis-alkenes?

Accepted Answer

Lindlar catalyst

Question 15

What is the major product when 2-methyl-2-butene reacts with $$HBr$$ and a 1,2-hydride shift occurs?

Accepted Answer

2-bromo-2-methylbutane

Question 16

Which of the following is a real-world application of alkene ozonolysis?

Accepted Answer

Cleavage of double bonds in fatty acids to determine their structure.

Question 17

Which product is formed when 1-butene reacts with $$Br_2 in$$ $$H_2O$$?

Accepted Answer

2-bromo-1-butanol

Question 18

Why does water not react with alkenes in the absence of acid?

Accepted Answer

Water is not acidic enough to act as an electrophile and initiate the reaction.

Question 19

Which of the following best describes the regioselectivity of electrophilic addition to alkenes?

Accepted Answer

The electrophile adds to the sp$$^2$$ carbon bonded to the most hydrogens.

Electrophilic Addition Reactions of Alkenes and Alkynes: Mechanisms, Regioselectivity, and Carbocation Rearrangements

Study Guide - Practice Questions