Question 1

Which of the following statements best explains why a strong leaving group is necessary for a reaction with a leaving group pKa of $$-15 to $$proceed efficiently?

Accepted Answer

A strong leaving group stabilizes the negative charge after departure, lowering the activation energy.

Question 2

Given the following compounds, rank them from most to least reactive in an SN1 reaction: $$\mathrm{(CH_3$)_3CBr}$$, $$\mathrm{CH_3CH_2Br}$$, $$\mathrm{C_6H_5CH_2Br}$$, $$\mathrm{CH_3Br}.$$

Accepted Answer

$$\mathrm{C_6H_5CH_2Br} \u003e \mathrm{(CH_3$)_3CBr} \u003e \mathrm{CH_3CH_2Br} \u003e \mathrm{CH_3Br}$$

Question 3

Which of the following best describes why neither product D nor E from question 2 rotates plane-polarized light?

Accepted Answer

D is a racemic mixture; E is achiral.

Question 4

Which of the following is the correct order of acidity for the following compounds: $$\mathrm{CH_3COOH}$$, $$\mathrm{CH_3OH}$$, $$\mathrm{H_2O}$$, $$\mathrm{C_6H_5OH}$$?

Accepted Answer

$$\mathrm{CH_3COOH} \u003e \mathrm{C_6H_5OH} \u003e \mathrm{H_2O} \u003e \mathrm{CH_3OH}$$

Question 5

A reaction produces two stereoisomers as products. What is the relationship between these products if they are non-superimposable mirror images?

Accepted Answer

They are enantiomers.

Question 6

Which of the following best explains the driving force for the reaction of an epoxide with a nucleophile under acidic conditions?

Accepted Answer

Relief of ring strain and formation of a stable alcohol.

Question 7

Which of the following functional groups is more reactive toward nucleophilic addition: aldehyde or ketone? Why?

Accepted Answer

Aldehyde, because it is less sterically hindered and more electrophilic.

Question 8

Which of the following is the correct order of basicity for the following compounds: $$\mathrm{NH_3$}$$, $$\mathrm{CH_3NH_2}$$, $$\mathrm{C_6H_5NH_2}$$, $$\mathrm{(CH_3$)_2NH}$$?

Accepted Answer

$$\mathrm{(CH_3$)_2NH} \u003e \mathrm{CH_3NH_2} \u003e \mathrm{NH_3$} \u003e \mathrm{C_6H_5NH_2}$$

Question 9

Which of the following best describes the maximum number of new chiral centers that can result when HCl is added to a diene with the formula $$\mathrm{C$$_{10}$$H_{18}}$$?

Accepted Answer

2

Question 10

Which of the following compounds reacts most readily with HCl: 1,3-cyclohexadiene, 1,4-cyclohexadiene, or cyclodecene? Why?

Accepted Answer

1,3-cyclohexadiene, because it forms a resonance-stabilized allylic carbocation.

Question 11

Which of the following best describes the relationship between the products formed from the reaction of cis-2-butene with Br$$_2 in $$CCl$$_4$$?

Accepted Answer

Enantiomers

Question 12

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

Accepted Answer

Protonation of the alkene to form a carbocation, followed by nucleophilic attack by water, then deprotonation.

Question 13

Which of the following best explains why a tertiary alkyl halide reacts faster than a primary alkyl halide in an SN1 reaction?

Accepted Answer

Tertiary carbocations are more stabilized by hyperconjugation and inductive effects.

Question 14

Which of the following is the correct order of reactivity toward nucleophilic acyl substitution: acid chloride, ester, amide, anhydride?

Accepted Answer

Acid chloride \u003e anhydride \u003e ester \u003e amide

Question 15

Which of the following best describes the product of the reaction of 1,3-butadiene with HBr at low temperature?

Accepted Answer

1,2-addition product is favored due to kinetic control.

Organic Chemistry Exam II Study Guidance

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