Question 1

Which of the following best explains why the hydroxy group in a phenol is more acidic than the hydroxy group in a secondary alcohol?

Accepted Answer

The phenol hydroxy group is more acidic because the negative charge on the conjugate base is delocalized by resonance into the aromatic ring.

Question 2

Consider the following reaction: $$\mathrm{Br_2$}$$ addition to cyclopentene in water. Which statement best describes the stereochemistry of the product?

Accepted Answer

The reaction produces a racemic mixture of trans-1,2-bromohydrin due to anti addition.

Question 3

Which of the following correctly describes the hybridization and geometry of a nitrile carbon?

Accepted Answer

sp hybridized, linear geometry

Question 4

In the hydroboration-oxidation of an alkene, which of the following statements is true regarding regioselectivity and stereochemistry?

Accepted Answer

Hydroboration is syn addition and anti-Markovnikov, while oxidation retains configuration (stereospecific).

Question 5

Which of the following best explains why a tertiary amine is a stronger base than a nitrile?

Accepted Answer

The nitrogen in a tertiary amine is sp$$^3$$ hybridized, making its lone pair more available for protonation than the sp hybridized nitrogen in a nitrile.

Question 6

Which of the following statements about the acid-catalyzed hydration of an alkyne is correct?

Accepted Answer

The reaction proceeds via Markovnikov addition, forming a ketone through enol-keto tautomerization.

Question 7

In the reaction of cyclopentene with $$\mathrm{Br_2$} in $$water, what is the major product?

Accepted Answer

trans-2-bromocyclopentanol

Question 8

Which of the following best describes the mechanism of the reaction between a terminal alkyne and $$\mathrm{$$NaNH_2$$}$$ followed by $$\mathrm{CH_3I}$$?

Accepted Answer

Deprotonation of the terminal alkyne forms an acetylide ion, which then undergoes $$\mathrm{S_N2}$$ alkylation with $$\mathrm{CH_3I}.$$

Question 9

Which of the following is a correct statement about the stereochemistry of the product formed in the reaction of an epoxide with $$\mathrm{NaOH} in $$water?

Accepted Answer

The product is a trans-1,2-diol due to anti addition (backside attack).

Question 10

Which of the following statements about the hydration of alkynes using $$\mathrm{BH_3$}$$ followed by $$\mathrm{H_2O_2}$$ and $$\mathrm{NaOH} is $$correct?

Accepted Answer

The reaction gives anti-Markovnikov addition, resulting in an aldehyde as the major product.

Question 11

Which of the following best explains why the positive charge in a nitrile is less stabilized than in a tertiary amine?

Accepted Answer

The sp hybridized nitrogen in a nitrile holds the positive charge closer to the nucleus, making it less stabilized.

Question 12

Which of the following is the correct product for the reaction of 1-butyne with $$\mathrm{H_2O}$$, $$\mathrm{H_2SO_4}$$, and $$\mathrm{$$HgSO_4$$}$$?

Accepted Answer

2-butanone

Question 13

Which of the following statements about the formation of a bromonium ion intermediate in alkene reactions is correct?

Accepted Answer

The bromonium ion intermediate leads to anti addition of nucleophiles across the double bond.

Question 14

Which of the following best describes the product of the reaction of phenylacetylene with $$\mathrm{$$NaNH_2$$}$$ followed by ethylene oxide and water?

Accepted Answer

A phenyl-substituted alcohol with a two-carbon chain extension

Question 15

Which of the following is a correct statement about the selectivity of hydroboration-oxidation versus acid-catalyzed hydration of alkenes?

Accepted Answer

Hydroboration-oxidation gives anti-Markovnikov alcohols, while acid-catalyzed hydration gives Markovnikov alcohols.

Question 16

Which of the following is the best explanation for why the nucleophile in an $$\mathrm{S_N2}$$ reaction must be added after the acid workup in the synthesis of a terminal alkyne?

Accepted Answer

If the nucleophile and acid are added together, the nucleophile will be protonated and rendered inactive.

Question 17

Which of the following statements about the formation of diols from epoxides is correct?

Accepted Answer

Opening an epoxide with base gives a trans-diol due to backside attack.

Question 18

Which of the following is the correct product for the reaction of 1-phenyl-1-propyne with $$\mathrm{H_2O}$$, $$\mathrm{H_2SO_4}$$, and $$\mathrm{$$HgSO_4$$}$$?

Accepted Answer

1-phenyl-2-propanone

Organic Chemistry: Reaction Mechanisms, Stereochemistry, and Synthesis Practice (Exam 4 Key)

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