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

$$\Delta H^\circ \u003e 0$$ \text{ and } $$\Delta S^\circ \u003e 0$$

Question 1

Which of the following statements is true regarding the chair conformations of trans-1,3-diethylcyclohexane?

Accepted Answer

The two chair conformations are equal in energy.

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 compound shown below?

[Structure: bicyclic system with a bridge]

Accepted Answer

Bridged bicyclic

Question 4

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

Accepted Answer

$$\mathrm{CH_2Cl_2}^\cdot + \mathrm{Cl_2$} \rightarrow \mathrm{CHCl_2Cl} + \mathrm{Cl}^\cdot$$

Question 5

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

Accepted Answer

$$3$$

Question 6

What term describes the structural relationship between (2R,3S)-2,3,4-trichloropentane and (2S,3R,4S)-2,3,4-trichloropentane?

Accepted Answer

Diastereomers

Question 7

Glucose has a specific rotation of $$+52.8^\circ. $$Predict the concentration of a glucose aqueous solution contained in a 10 cm polarimetry tube if a rotation of $$+15.5^\circ$$ was observed. $$[\alpha] = \frac{	ext{observed rotation}}{l \cdot c}$$, where $$l is $$path length in dm and $$c is $$concentration in g/mL.

Accepted Answer

$$0.293\ \mathrm{g/mL}$$

Question 8

Which of the following species is the least nucleophilic?

Accepted Answer

$$\mathrm{BF_3$}$$

Question 9

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

Accepted Answer

1-iodobutane

Question 10

Consider the bond dissociation energies listed below in kcal/mol:
(CH$$_3$$)$$_2CH$$–Br: 68
CH$$_3CH$_2$$–Br: 68
(CH$$_3$$)$$_3C$$–Br: 65
(CH$$_2Br$$)–CH$$_2$$–CH$$_3$$: 68
These data show that the carbon–bromine bond is weakest when bromine is bound to a:

Accepted Answer

Tertiary carbon

Question 11

List the following radicals in order of increasing stability (least 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 12

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

Accepted Answer

$$\Delta H^\circ \u003e 0$$ 	ext{ and } $$\Delta S^\circ \u003e 0$$

Question 13

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

Accepted Answer

Both A and C

Question 14

Which of the following is a secondary halide?

Accepted Answer

$$(\mathrm{CH_3$})_2CHCHClCH_3$$

Question 15

Which of the following terms best describes the pair of compounds shown below?

[Structure: two molecules with identical connectivity and stereochemistry]

Accepted Answer

Same compound

Question 16

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

Accepted Answer

IV

Question 17

Which of the following is a diastereomer of the molecule below?

[Structure: 2,3-dibromopentane]

Accepted Answer

$$(2R,3S)-2$$,3-dibromopentane

Question 18

Which of the following carbon–halide bonds is expected to be the weakest?

Accepted Answer

Tertiary carbon–bromine

Question 19

Which of the following best describes the major product of the reaction below?

$$\mathrm{CH_3COCH_2CH_3} + \mathrm{NaCN} \rightarrow$$

Accepted Answer

$$\mathrm{CH_3COCH(CN)CH_3$}$$

Organic Chemistry: Cycloalkanes, Stereochemistry, and Radical Reactions (Exam Study Guide)

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