Question 1

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

Accepted Answer

Each carbon atom alternates between axial and equatorial positions during a ring flip.

Question 2

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

Accepted Answer

$$4$$

Question 3

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

Accepted Answer

enantiomers

Question 4

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

Accepted Answer

$$\mathrm{Cl_2$} + \cdot\mathrm{CH_2Cl} \rightarrow \mathrm{CH_2Cl_2} + \cdot\mathrm{Cl}$$

Question 5

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

Accepted Answer

Both A and B

Question 6

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

The carbon in $$\mathrm{CH_2Br-CH_2Br}$$

Question 9

Which of the following is a secondary halide?

Accepted Answer

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

Question 10

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

Accepted Answer

$$3$$

Question 11

Which of the following best describes the compound below? (Bicyclo[2.2.1]heptane structure)

Accepted Answer

Bridged bicyclic

Question 12

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

Accepted Answer

$$\Delta H \u003e 0$$~and~$$\Delta S \u003e 0$$

Question 13

Which of the following statements correctly describes the chair conformations of trans-1,3-dimethylcyclohexane?

Accepted Answer

The lower energy chair conformation contains two equatorial methyl groups.

Question 14

In the lowest energy chair conformation of the compound below (1,4-dimethylcyclohexane), how many alkyl substituents are equatorial?

Accepted Answer

$$2$$

Question 15

Which of the following terms best describes the pair of compounds shown below? (One is (R,R)-2,3-dibromobutane, the other is (S,S)-2,3-dibromobutane)

Accepted Answer

Enantiomers

Question 16

Which of the following is the correct order of radical stability (from least stable to most stable) for the following radicals: $$(CH_3$)_3C\cdot$$, $$CH_2$$=$$CHCH_2$$\cdot$$, CH_3CH_2$$\cdot$$, CH_3$\cdot$$, $$(CH_3$)_2CH\cdot$$?

Accepted Answer

$$CH_3$$\cdot \u003c CH_3CH_2\cdot \u003c ($$CH_3)_2CH$$\cdot \u003c ($$CH_3)_3C$$\cdot \u003c $$CH_2$$=$$CHCH_2$$\cdot$$

Question 17

Which of the following best explains why tertiary alkyl halides do not undergo $$\mathrm{S_N2}$$ reactions efficiently?

Accepted Answer

Steric hindrance at the reaction center prevents backside attack by the nucleophile.

Question 18

A solution of glucose has a specific rotation of $$+52.8^\circ. $$What is 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? (Assume $$[\alpha] = +52.8^\circ)$$

Accepted Answer

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

Question 19

Which of the following is a correct initiation step for the free radical bromination of methane?

Accepted Answer

$$Br_2 + hv$$ \rightarrow 2Br\cdot$$

Question 20

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

Accepted Answer

Diastereomers

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

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