Question 1

Which of the following statements about the chair conformations of cyclohexane is correct?

Accepted Answer

The chair conformation of cyclohexane minimizes torsional strain and is the most stable conformation.

Question 2

In the lowest energy chair conformation of cis-1,3-dimethylcyclohexane, how many axial positions are occupied by hydrogen atoms?

Accepted Answer

$$5$$

Question 3

Which of the following best describes the relationship between (2R,3S,4R)-2,3,4-trichlorheptane and (2S,3R,4S)-2,3,4-trichlorheptane?

Accepted Answer

Diastereomers

Question 4

Which of the following is a propagation step in the free radical chlorination of dichloromethane?

Accepted Answer

$$\mathrm{CH_2Cl_2^\cdot} + \mathrm{Cl_2$} \rightarrow \mathrm{$$CHCl_2$$} + \mathrm{Cl^\cdot}$$

Question 5

How do alkyl substituents stabilize a carbocationic center to which they are attached?

Accepted Answer

Both A and C

Question 6

Which of the following alkyl halides reacts most rapidly via an $$S_N2$$ reaction with $$\mathrm{NaCN}$$?

Accepted Answer

1-iodobutane

Question 7

Which of the following species is the least nucleophilic?

Accepted Answer

$$\mathrm{BF_3$}$$

Question 8

Given the bond dissociation energies: $$\mathrm{CH_3$-Br}$$: $$68~\mathrm{kcal/mol}$$, $$\mathrm{CH_2Br-CH_2Br}$$: $$65~\mathrm{kcal/mol}$$, $$\mathrm{CH_3CH_2-Br}$$: $$68~\mathrm{kcal/mol}$$, which carbon-bromine bond is weakest?

Accepted Answer

Secondary carbon

Question 9

List the following radicals in order of increasing stability (least stable to most stable): $$\mathrm{(CH_3$)_3C^\cdot}$$, $$\mathrm{CH_2$=$$CHCH_2$$^\cdot}$$, $$\mathrm{CH_3CH_2^\cdot}$$, $$\mathrm{CH_3$^\cdot}$$, $$\mathrm{(CH_3$)_2CH^\cdot}.$$

Accepted Answer

$$\mathrm{CH_3$^\cdot} \u003c \mathrm{CH_3CH_2^\cdot} \u003c \mathrm{(CH_3$)_2CH^\cdot} \u003c \mathrm{(CH_3$)_3C^\cdot} \u003c \mathrm{CH_2$=$$CHCH_2$$^\cdot}$$

Question 10

Which of the following is a secondary halide?

Accepted Answer

$$\mathrm{CH_3CH_2CH(CH_3$)Br}$$

Question 11

Which of the following is true for the initiation step of a free radical chlorination reaction?

Accepted Answer

$$\Delta H^\circ \u003e 0$$~and~$$\Delta S^\circ \u003c 0$$

Question 12

How many distinct dichlorination products can result when isobutane is subjected to free radical chlorination?

Accepted Answer

$$4$$

Question 13

Which of the following best describes the compound shown below? (A bicyclic structure with two bridges)

Accepted Answer

Bridged bicyclic

Question 14

Glucose has a specific rotation of $$+52.8^\circ. $$Predict the concentration of a glucose aqueous solution contained in a $$10~\mathrm{cm}$$ long polarimetry tube if a rotation of $$+15.8^\circ$$ was observed. $$[\alpha] = \frac{\alpha_{obs}}{l \cdot c}$$

Accepted Answer

$$0.299~\mathrm{g/mL}$$

Question 15

Which of the following terms best describes the pair of compounds shown below? (One is R,R, the other is S,R at two chiral centers)

Accepted Answer

Diastereomers

Question 16

Which of the following structures corresponds to the correct configuration of D-Threonine ($$2R,3S$$)?

Accepted Answer

III

Question 17

Which of the following statements correctly describes the stereochemistry of the major product formed in the reaction of 3,4-dimethylhexane with chlorine?

Accepted Answer

Chlorine will preferentially substitute at the tertiary carbon due to radical stability.

Question 18

Which of the following best explains why the $$S_N2$$ reaction rate decreases as the steric bulk of the alkyl halide increases?

Accepted Answer

Steric hindrance slows the approach of the nucleophile to the electrophilic carbon.

Question 19

Which of the following is the major organic product of the reaction below? $$\mathrm{CH_3CH_2CH_2CH_2Br} + \mathrm{NaCN} \rightarrow$$

Accepted Answer

$$\mathrm{CH_3CH_2CH_2CH_2CN}$$

Organic Chemistry Exam Study Guide: Conformations, Stereochemistry, and Radical Reactions

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