Question 1

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

Accepted Answer

Tertiary carbocations are stabilized by hyperconjugation and inductive effects from three alkyl groups.

Question 2

Which of the following molecules will NOT undergo an $$\mathrm{S_N2}$$ reaction, regardless of the nucleophile?

Accepted Answer

A tertiary alkyl halide due to steric hindrance.

Question 3

Which of the following best describes Markovnikov’s rule as it applies to the addition of $$\mathrm{HBr} to $$propene?

Accepted Answer

The bromine atom attaches to the more substituted carbon atom.

Question 4

Which of the following is the correct order of acidity (most to least acidic) for the following compounds: acetic acid, ethanol, water, and methane?

Accepted Answer

$$\mathrm{CH_3COOH \u003e H_2O \u003e CH_3CH_2OH \u003e CH_4$}$$

Question 5

Why can the following molecule not undergo an $$\mathrm{E2}$$ elimination reaction: $$\mathrm{CH_3CH_2Br} in $$the presence of a strong base?

Accepted Answer

The leaving group is not anti-periplanar to a hydrogen.

Question 6

Which of the following best explains why an alkene is a better nucleophile than an alkane?

Accepted Answer

Alkenes have a region of high electron density due to the $$\pi$$ bond.

Question 7

Which of the following best describes the first mechanistic step in the reaction of Freon ($$\mathrm{CCl_2F_2}) $$with UV light that leads to ozone depletion?

Accepted Answer

Homolytic cleavage of a $$\mathrm{C-Cl}$$ bond to generate a chlorine radical.

Question 8

Which of the following energy diagrams best represents a two-step reaction with a carbocation intermediate?

Accepted Answer

A diagram with two transition states and an intermediate valley between them.

Question 9

Which of the following reagents would convert 2-bromopropane to propene via an $$\mathrm{E2}$$ mechanism?

Accepted Answer

$$\mathrm{KOH} in $$ethanol

Question 10

Which of the following statements is TRUE regarding the stereochemistry of anti addition of bromine to cyclohexene?

Accepted Answer

The two bromine atoms add to opposite faces of the double bond, resulting in a trans product.

Question 11

Which of the following best explains why a tertiary alkyl halide reacts faster in an $$\mathrm{S_N1}$$ reaction than a primary alkyl halide?

Accepted Answer

Tertiary carbocations are more stable due to inductive and hyperconjugative effects.

Question 12

Which of the following is the correct sequence of steps for the acid-catalyzed hydration of an alkene?

Accepted Answer

Protonation of the alkene, formation of a carbocation, nucleophilic attack by water, deprotonation.

Question 13

Which of the following best describes the product of the reaction between 1-butene and $$\mathrm{Br_2$} in$$ $$\mathrm{$$CCl_4$$}$$?

Accepted Answer

A vicinal dibromide with anti stereochemistry.

Question 14

Which of the following is the best explanation for why a methyl group increases the stability of a carbocation?

Accepted Answer

It donates electron density through hyperconjugation and inductive effects.

Question 15

Which of the following is the correct order of stability for the following carbocations: methyl, primary, secondary, tertiary?

Accepted Answer

$$\mathrm{tertiary \u003e secondary \u003e primary \u003e methyl}$$

Question 16

Which of the following best explains why a cis-dibromide is not formed in the anti addition of $$\mathrm{Br_2$} to an $$alkene?

Accepted Answer

The reaction proceeds through a bromonium ion intermediate, which forces the bromines to add to opposite faces.

Question 17

Which of the following is the correct product for the reaction of 2-methyl-2-butene with $$\mathrm{HBr}$$?

Accepted Answer

2-bromo-2-methylbutane

Question 18

Which of the following best describes the effect of resonance on the acidity of phenol compared to cyclohexanol?

Accepted Answer

Resonance stabilization of the phenoxide ion increases the acidity of phenol.

Organic Chemistry Exam II Study Guidance

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