Question 1

Which of the following statements about bond-line (skeletal) structures is TRUE?

Accepted Answer

Only heteroatoms and hydrogens attached to them are explicitly shown; carbons are represented by corners or endpoints.

Question 2

Given the molecular formula $$\mathrm{C_3H_8O}$$, which representation would be INADEQUATE to distinguish between propanol and isopropanol?

Accepted Answer

Molecular formula

Question 3

In a bond-line structure, how many hydrogen atoms are implied to be attached to the terminal carbon in hexane ($$\mathrm{C_6H_{14}}$$)?

Accepted Answer

Three

Question 4

Which rule must ALWAYS be followed when drawing bond-line structures for organic molecules?

Accepted Answer

Never draw more than four bonds to a carbon atom.

Question 5

A carbon atom in a bond-line structure is shown with only three bonds and no lone pairs. What is its formal charge?

Accepted Answer

+1

Question 6

Which of the following is TRUE regarding the representation of lone pairs in bond-line structures?

Accepted Answer

Lone pairs are often omitted, but their presence is implied by formal charge.

Question 7

Which of the following best describes the use of dashed and solid wedges in bond-line structures?

Accepted Answer

They represent groups pointing into or out of the plane of the paper, indicating 3D geometry.

Question 8

Which of the following is NOT a valid resonance pattern described in Chapter 2?

Accepted Answer

Sigma bond between two atoms of different electronegativity

Question 9

When drawing resonance structures using curved arrows, which rule must be followed for second-row elements (B, C, N, O, F)?

Accepted Answer

They must never exceed an octet (eight electrons) in their valence shell.

Question 10

Which resonance structure is the most significant contributor to the resonance hybrid?

Accepted Answer

The structure with the greatest number of filled octets.

Question 11

In the allyl carbocation, how are the positive charge and pi electrons best described?

Accepted Answer

The pi electrons and positive charge are delocalized over all three carbon atoms.

Question 12

Which of the following statements about delocalized lone pairs is TRUE?

Accepted Answer

A lone pair is delocalized only if it is adjacent to an atom with an unhybridized p orbital.

Question 13

Which of the following is a correct application of curved arrows in resonance structures?

Accepted Answer

Curved arrows start at the location of electrons and end where the electrons will be after movement.

Question 14

Which of the following functional groups is characterized by a carbonyl group ($$\mathrm{C=O}) $$bonded to a nitrogen atom?

Accepted Answer

Amide

Question 15

A lone pair on a nitrogen atom is adjacent to a carbon with a pi bond. Under what condition will the lone pair NOT participate in resonance?

Accepted Answer

If the nitrogen atom also possesses a pi bond.

Question 16

Which of the following best explains why resonance stabilizes a molecule?

Accepted Answer

Delocalization allows electrons to occupy orbitals that span a greater distance, minimizing repulsions and maximizing attractions.

Question 17

Which of the following is TRUE about the resonance hybrid?

Accepted Answer

It represents the actual structure of the molecule, which is a blend of all possible resonance contributors.

Question 18

In a molecule with a pi bond between two atoms of different electronegativity, what is the effect on the pi electrons?

Accepted Answer

The pi electrons are more attracted to the more electronegative atom, resulting in partial charges.

Question 19

Which of the following statements about formal charges in resonance structures is CORRECT?

Accepted Answer

Formal charges must always be shown in resonance structures.

Question 20

Which of the following is a correct statement about the hybridization of nitrogen in a molecule where its lone pair participates in resonance?

Accepted Answer

The nitrogen atom must be sp2 hybridized, with the lone pair occupying a p orbital.

Molecular Representations and Resonance in Organic Chemistry

Study Guide - Practice Questions