Question 1

Which of the following statements best explains why the staggered conformation of n-butane is lower in energy than the eclipsed conformation when viewed down the C2—C3 bond axis?

Accepted Answer

Staggered conformations minimize torsional strain by maximizing the distance between adjacent bonds.

Question 2

During the free radical bromination of 2,3-dimethylbutane with $$\mathrm{Br_2$}$$ and heat, which carbon is most likely to be brominated and why?

Accepted Answer

A tertiary carbon, because tertiary radicals are stabilized by hyperconjugation and inductive effects.

Question 3

Which of the following is the correct Fischer projection for the (R)-configuration of the molecule shown below?

$$\mathrm{HOCH_2CH(OH)CH_3$}$$

Accepted Answer

The horizontal substituents point toward the viewer, and the vertical substituents point away.

Question 4

Which of the following pairs of molecules are diastereomers?

Accepted Answer

Two molecules with opposite configurations at one but not all chiral centers.

Question 5

Which functional group is present in the following molecule?

$$\mathrm{CH_3CH_2OH}$$

Accepted Answer

Alcohol

Question 6

Which compound has greater water solubility and why?

$$\mathrm{CH_3NH_2} vs$$. $$\mathrm{(CH_3$)_3N}$$

Accepted Answer

$$\mathrm{CH_3NH_2}$$, because it can form more hydrogen bonds with water.

Question 7

What is the hybridization of the positively charged carbon ion in the following carbocation?

$$\mathrm{C_6H_5C^+}$$

Accepted Answer

$$sp^2$$

Question 8

Which of the following compounds is chiral?

Accepted Answer

$$\mathrm{HOCH_2CH(OH)CH_3$}$$

Question 9

Which of the following statements about the relative strength of acids is correct?

Accepted Answer

A lower $$pK_a$$ value indicates a stronger acid.

Question 10

Which of the following elements has the highest electronegativity according to the Pauling scale?

Accepted Answer

Fluorine

Question 11

In the reaction $$\mathrm{CH_3CO_2H + CN^- \rightarrow CH_3CO_2^- + HCN}$$, which species acts as the acid?

Accepted Answer

$$\mathrm{CH_3CO_2H}$$

Question 12

Which of the following best describes the hybridization and geometry of the central carbon in $$\mathrm{CO_2$}$$?

Accepted Answer

$$sp$$ hybridized, linear geometry

Question 13

Which of the following is the correct order of increasing acidity for the following acids: $$\mathrm{CH_3CO_2H}$$, $$\mathrm{H_2O}$$, $$\mathrm{HCN}$$?

Accepted Answer

$$\mathrm{HCN \u003c H_2O \u003c CH_3CO_2H}$$

Question 14

Which of the following is a meso compound?

Accepted Answer

A compound with two chiral centers and a plane of symmetry.

Question 15

Which of the following best explains why $$\mathrm{Br_2$}$$ reacts with alkanes under UV light?

Accepted Answer

UV light initiates homolytic cleavage of the Br-Br bond, generating bromine radicals.

Question 16

Which of the following is the correct hybridization for the nitrogen atom in acetonitrile ($$\mathrm{CH_3CN}$$)?

Accepted Answer

$$sp$$

Question 17

Which of the following is the correct Lewis structure for the cyanide ion ($$\mathrm{CN^-}$$)?

Accepted Answer

A triple bond between C and N, with a lone pair on C and a negative charge on N.

Question 18

Which of the following best describes the relationship between electronegativity and acid strength?

Accepted Answer

As electronegativity increases, acid strength increases.

Question 19

Which of the following is the correct mechanism for the reaction of $$\mathrm{CH_3CH_2Br}$$ with $$\mathrm{OH^-} in $$water?

Accepted Answer

SN2 substitution

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