Question 1

Which hybridization is present at the nitrogen atom in pyridine?

Accepted Answer

$$sp^2$$

Question 2

In the enolate ion shown, which atom carries the negative charge in the major resonance contributor?

Accepted Answer

The oxygen atom

Question 3

Which orbital contains the lone pair on the nitrogen atom in pyridine?

Accepted Answer

$$sp^2$$

Question 4

Which of the following is the best resonance structure for the methyl isocyanate molecule?

Accepted Answer

The structure with a triple bond between carbon and nitrogen

Question 5

Rank the following orbitals from worst to best donor abilities: $$C=C$$, $$C=O$$, $$C\equiv N$$, $$C\equiv C$$, $$C=Cl.$$

Accepted Answer

$$C=Cl \u003c C=O \u003c C\equiv N \u003c C\equiv C \u003c C=C$$

Question 6

Which resonance structure of the allyl carbocation is the most stable?

Accepted Answer

The one with the positive charge delocalized over both terminal carbons

Question 7

What is the hybridization of the carbon atom in the carbonyl group of an enolate?

Accepted Answer

$$sp^2$$

Question 8

Which of the following best explains why the alkene carbons in the given structure have partial charges?

Accepted Answer

Resonance delocalizes electron density, creating a partial negative charge on one carbon and a partial positive charge on the other.

Question 9

Which orbital is the best acceptor among the following: $$C=O^+$$, $$C=C^+$$, $$C\equiv C^+$$, $$C\equiv N^+$$, $$C=B$$?

Accepted Answer

$$C=O^+$$

Question 10

Which of the following is NOT a valid resonance structure for pyridine?

Accepted Answer

A structure with a triple bond between two carbons in the ring

Question 11

In the resonance hybrid of the enolate ion, what is the bond order between the carbon and oxygen atoms?

Accepted Answer

1.5

Question 12

Which of the following statements about lone pairs in $$sp^2$$ hybridized atoms is correct?

Accepted Answer

Lone pairs occupy $$sp^2$$ orbitals and are not involved in resonance.

Question 13

Which of the following molecules is most likely to act as a nucleophile in a reaction?

Accepted Answer

Enolate ion

Question 14

What is the effect of resonance on the stability of the allyl carbocation?

Accepted Answer

Resonance increases stability by delocalizing the positive charge.

Question 15

Which of the following best describes the hybridization of the carbon atom in methyl isocyanate adjacent to the nitrogen?

Accepted Answer

$$sp$$

Question 16

Which resonance structure of the enolate ion is the least stable?

Accepted Answer

The one with the negative charge on the carbon atom

Question 17

Which of the following is a common misconception about resonance structures?

Accepted Answer

Resonance structures are in equilibrium with each other.

Question 18

Which atom in pyridine is most likely to participate in hydrogen bonding as an acceptor?

Accepted Answer

Nitrogen

Question 19

Which of the following best describes the electron distribution in the resonance hybrid of methyl isocyanate?

Accepted Answer

Electron density is delocalized between the carbon, nitrogen, and oxygen atoms.

Question 20

Which of the following statements about the donor ability of $$C=C$$ compared to $$C=O is $$correct?

Accepted Answer

$$C=C is a $$better donor than $$C=O$$ due to lower electronegativity of carbon.

Puzzle Set #3

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