Question 1

Which of the following best describes the use of curved arrows in organic reaction mechanisms?

Accepted Answer

Curved arrows represent the movement of electrons, either as pairs (double-barbed) or single electrons (single-barbed).

Question 2

Which of the following is a necessary condition for resonance to occur in a molecule?

Accepted Answer

Conjugation of parallel unhybridized p orbitals on three or more consecutive atoms.

Question 3

Why is benzene more stable than expected for a molecule with alternating double bonds?

Accepted Answer

Benzene is aromatic, possessing a cyclic, uninterrupted system of $$4n+2$$ $$	ext{π}$$ electrons, which leads to extra stability.

Question 4

Which of the following resonance structures is least likely to contribute to the overall electronic structure of a molecule?

Accepted Answer

A structure with opposite charges on adjacent carbon atoms.

Question 5

Given the following acid/base reaction: $$HA + H_2O \rightarrow A^- + H_3O^+$$, which factor most directly increases the acidity of $$HA$$?

Accepted Answer

The stability of the conjugate base $$A^-.$$

Question 6

Which of the following statements about $$pK_a is $$correct?

Accepted Answer

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

Question 7

Which of the following molecules would have the highest acidity based on the atom bonded to the acidic proton?

Accepted Answer

Hydrofluoric acid ($$HF)$$

Question 8

How does resonance affect the acidity of carboxylic acids compared to alcohols?

Accepted Answer

Resonance in carboxylic acids stabilizes the conjugate base, making them more acidic than alcohols.

Question 9

Which of the following best explains why trifluoroacetic acid ($$CF_3COOH) is a $$much stronger acid than acetic acid ($$CH_3COOH$$)?

Accepted Answer

The fluorine atoms withdraw electron density through inductive effects, stabilizing the conjugate base.

Question 10

Which of the following is true regarding the effect of hybridization on acidity?

Accepted Answer

An sp hybridized carbon is more acidic than an sp2 or sp3 hybridized carbon.

Question 11

Which of the following is the correct formula for calculating $$K_{eq}$$ for an acid/base reaction using $$pK_a$$ values?

Accepted Answer

$$K_{eq} = 10$$^{pK_a(HB) - pK_a(HA)}$$

Question 12

Which of the following compounds is aromatic?

Accepted Answer

Benzene (6 $$	ext{π}$$ electrons)

Question 13

Which of the following is a Brønsted-Lowry base?

Accepted Answer

A molecule that accepts a proton ($$H^+)$$

Question 14

Which factor does NOT contribute to the stability of a conjugate base?

Accepted Answer

Presence of opposite charges on adjacent carbons

Question 15

Which of the following statements about anti-aromatic compounds is correct?

Accepted Answer

Anti-aromatic compounds have cyclic, uninterrupted $$	ext{π}$$ systems with $$4n$$ $$	ext{π}$$ electrons and are less stable than expected.

Question 16

Which of the following is the correct expression for the acid dissociation constant $$K_a$$ for the reaction $$HA + H_2O \rightarrow A^- + H_3O^+$$?

Accepted Answer

$$K_a = \frac{[A^-][H_3O^+]}{[HA]}$$

Question 17

Which of the following everyday substances acts as a base due to its ability to accept protons?

Accepted Answer

Baking soda (sodium bicarbonate)

Question 18

Which of the following amines is the most basic?

Accepted Answer

Ethylamine ($$CH_3CH_2NH_2)$$

Question 19

Which factor would most increase the acidity of an alcohol?

Accepted Answer

Attachment of electron-withdrawing groups such as fluorine

Arrows, Resonance, and Acid/Base Chemistry: Foundations in Organic Chemistry

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