Question 1

Which of the following best describes the bond-line structure convention for organic molecules?

Accepted Answer

Carbons are only shown at the ends and bends of lines, and hydrogens attached to carbons are implied.

Question 2

Given the condensed formula $$\mathrm{CH_3CH_2OH}$$, which of the following is the correct Lewis structure?

Accepted Answer

A two-carbon chain with an -OH group attached to the second carbon and all hydrogens explicitly drawn.

Question 3

Which of the following is NOT a correct rule for drawing bond-line structures?

Accepted Answer

Hydrogens attached to carbons are always shown explicitly.

Question 4

Which functional group is present in the molecule shown in the first image (isopropanol)?

Accepted Answer

Alcohol

Question 5

In the context of three-dimensional drawings, what does a wedge represent?

Accepted Answer

A bond coming out of the plane of the page.

Question 6

Which of the following is the correct molecular formula for a molecule with 5 carbons, 9 hydrogens, and 1 chlorine atom?

Accepted Answer

$$\mathrm{C_5H_9Cl}$$

Question 7

Which of the following statements about lone pairs in bond-line structures is TRUE?

Accepted Answer

Lone pairs on heteroatoms are optional but encouraged for clarity.

Question 8

A carbocation is best described as:

Accepted Answer

A carbon atom with three bonds and a positive charge, possessing an empty $$p$$ orbital.

Question 9

Which of the following is a correct statement about resonance structures?

Accepted Answer

Resonance structures differ only in the location of $$\pi$$ electrons and lone pairs.

Question 10

Which of the following curved arrow movements is NOT allowed when drawing resonance structures?

Accepted Answer

Breaking a $$\sigma$$ bond.

Question 11

Which of the following is the most significant resonance contributor for a molecule?

Accepted Answer

The structure with the most filled octets and minimal formal charges.

Question 12

Which of the following best describes a conjugated system?

Accepted Answer

A system with alternating single and double bonds, allowing $$\pi$$ electrons to be delocalized over three or more adjacent atoms.

Question 13

Which of the following functional groups contains a carbonyl group directly bonded to a nitrogen atom?

Accepted Answer

Amide

Question 14

Which of the following is a correct statement about localized and delocalized lone pairs?

Accepted Answer

Delocalized lone pairs are found in $$p$$ orbitals and participate in resonance.

Question 15

Which of the following is the correct pattern for drawing resonance structures involving an allylic lone pair?

Accepted Answer

Two curved arrows: one moving the lone pair to form a $$\pi$$ bond, and one moving the $$\pi$$ bond to form a lone pair.

Question 16

Which of the following is a constitutional isomer?

Accepted Answer

Two molecules with the same molecular formula but different connectivity of atoms.

Question 17

Which of the following is TRUE regarding the formal charge on atoms in resonance structures?

Accepted Answer

The sum of formal charges must remain constant across all resonance structures.

Question 18

Which of the following best describes the difference between a nucleophile and an electrophile?

Accepted Answer

A nucleophile is electron-rich and seeks positive centers, while an electrophile is electron-poor and seeks electrons.

Question 19

Which of the following is NOT a significant resonance contributor?

Accepted Answer

A structure with a carbon atom having only six electrons in its valence shell.

Question 20

Which of the following statements about resonance hybrids is correct?

Accepted Answer

A resonance hybrid is a weighted average of all significant resonance contributors, showing partial bonds and charges.

Molecular Representations and Resonance in Organic Chemistry

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