Question 1

Which of the following statements best describes Markovnikov's rule as it applies to the addition of HX to an unsymmetrical alkene?

Accepted Answer

The hydrogen (H) adds to the less substituted carbon, and the halide (X) adds to the more substituted carbon of the double bond.

Question 2

During the halogenation of cyclohexene with $$\mathrm{Br_2$}$$, which intermediate is formed and what is the stereochemical outcome?

Accepted Answer

A bromonium ion intermediate is formed, resulting in anti addition and a racemic mixture of enantiomers.

Question 3

Which of the following best explains why hydroboration-oxidation of an alkene results in anti-Markovnikov addition of water?

Accepted Answer

The boron atom adds to the less substituted carbon, and subsequent oxidation replaces boron with OH, resulting in anti-Markovnikov alcohol.

Question 4

A terminal alkyne is treated with $$\mathrm{$$NaNH_2$$}$$ followed by $$\mathrm{CH_3CH_2Br}. $$What is the major product of this reaction sequence?

Accepted Answer

An internal alkyne with an ethyl group added to the terminal carbon.

Question 5

Which of the following bases is strong enough to deprotonate a terminal alkyne (p$$K_a$$ ≈ 25)?

Accepted Answer

$$\mathrm{NaH}$$

Question 6

In the retrosynthetic analysis of 2-pentanone, which of the following is a plausible immediate precursor using an alkylation strategy?

Accepted Answer

An acetylide anion and 1-bromopropane

Question 7

Which of the following correctly describes the stereochemical outcome of the addition of $$\mathrm{Br_2$} to $$trans-2-butene?

Accepted Answer

A meso compound is formed due to anti addition.

Question 8

Which of the following statements about the mechanism of alkene halogenation is correct?

Accepted Answer

The halogen adds via a three-membered cyclic halonium ion intermediate, preventing rearrangements.

Question 9

Which of the following best describes the regiochemistry and stereochemistry of hydroboration-oxidation of 1-methylcyclohexene?

Accepted Answer

Anti-Markovnikov addition, syn addition

Question 10

A student is asked to predict the product of the reaction of 1-butyne with excess $$\mathrm{HBr}. $$Which of the following is correct?

Accepted Answer

2,2-dibromobutane is formed via Markovnikov addition.

Question 11

Which of the following is NOT a possible product when 2-butyne is treated with excess $$\mathrm{Br_2$}$$?

Accepted Answer

2,3,3,4-tetrabromobutane

Question 12

Which of the following statements about retrosynthetic analysis is correct?

Accepted Answer

It involves working backward from the target molecule to simpler precursors.

Question 13

Which of the following best explains why halogenation of alkenes is stereospecific?

Accepted Answer

The reaction proceeds through a cyclic halonium ion, leading to anti addition.

Question 14

Which of the following is the correct order of increasing acidity (lower to higher p$$K_a) $$for the following: water, ammonia, terminal alkyne?

Accepted Answer

Ammonia \u003c water \u003c terminal alkyne

Question 15

Which of the following statements about the addition of $$\mathrm{H_2O} to an $$alkyne in the presence of $$\mathrm{$$HgSO_4$$}$$ and $$\mathrm{H_2SO_4} is $$correct?

Accepted Answer

The reaction gives a ketone via Markovnikov addition.

Question 16

Which of the following is the correct product when 1-hexyne is treated with $$\mathrm{BH_3$}$$ followed by $$\mathrm{H_2O_2}$$ and $$\mathrm{NaOH}$$?

Accepted Answer

Hexanal

Question 17

Which of the following best describes the selectivity of hydroboration-oxidation of terminal alkynes?

Accepted Answer

Anti-Markovnikov addition, forming an aldehyde

Question 18

A student is asked to synthesize 2-pentanone from a terminal alkyne. Which of the following sequences is most appropriate?

Accepted Answer

Alkylation with $$\mathrm{EtBr}$$, followed by hydration with $$\mathrm{$$HgSO_4$$}$$/$$\mathrm{H_2SO_4}$$

Question 19

Which of the following statements about syn and anti addition is correct?

Accepted Answer

Syn addition occurs when two groups add to the same face of a double bond.

Key Concepts for Organic Chemistry I: Addition Reactions, Selectivity, and Retrosynthetic Analysis

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