Q: Which of the following statements best explains why benzene is more stable than 1,3,5-cyclohexatriene?

Benzene undergoes resonance, delocalizing its $$ ext{6} \\pi$$ electrons over all six carbon atoms.

Q: Rank the following compounds in order of increasing acidity: ethyne, ethanol, ethene, and ethane.

$$\\text{ethane} \u003c \\text{ethene} \u003c \\text{ethanol} \u003c \\text{ethyne}$$

Q: Which of the following benzene derivatives is most deactivated toward electrophilic aromatic substitution (EAS)?

Benzenesulfonic acid ($$\\text{SO}_3\\text{H}$$ group)

Q: Predict the major product(s) for the following reaction: cyclopentanone + NaCN, then H$$_2O.$$

A cyanohydrin is formed: $$\\text{NCCH(OH)cyclopentane}$$

Q: Which of the following is the correct order of reactivity for electrophilic aromatic substitution (EAS) for the following substituents: $$\\text{NO}_2$$, $$\\text{OCH}_3$$, $$\\text{Cl}$$, $$\\text{NH}_2$$?

$$\\text{NO}_2 \u003c \\text{Cl} \u003c \\text{OCH}_3 \u003c \\text{NH}_2$$

Question 1

Which of the following statements best explains why benzene is more stable than 1,3,5-cyclohexatriene?

Accepted Answer

Benzene undergoes resonance, delocalizing its $$	ext{6} \pi$$ electrons over all six carbon atoms.

Question 2

Rank the following compounds in order of increasing acidity: ethyne, ethanol, ethene, and ethane.

Accepted Answer

$$\text{ethane} \u003c \text{ethene} \u003c \text{ethanol} \u003c \text{ethyne}$$

Question 3

Which of the following benzene derivatives is most deactivated toward electrophilic aromatic substitution (EAS)?

Accepted Answer

Benzenesulfonic acid ($$\text{SO}_3\text{H}$$ group)

Question 4

Which of the following would be the worst dienophile for a Diels-Alder reaction?

Accepted Answer

Ethylene

Question 5

What is the IUPAC name for a compound with a benzene ring substituted with an amino group at position 1, a nitro group at position 2, and a bromo group at position 4?

Accepted Answer

2-bromo-4-nitroaniline

Question 6

Predict the major product(s) for the following reaction: cyclopentanone + NaCN, then H$$_2O.$$

Accepted Answer

A cyanohydrin is formed: $$\text{NCCH(OH)cyclopentane}$$

Question 7

How many p-orbitals and atoms in conjugation are present in the following compound: $$\text{CH}_2=CH-CH=CH-CH_2$-CH=CH_2$?

Accepted Answer

7 p-orbitals, 7 atoms in conjugation

Question 8

Which structure is the most stable and which is the least stable among the following cycloalkanes: cyclopropane, cyclobutane, cyclopentane, cyclohexane?

Accepted Answer

Cyclohexane is most stable, cyclopropane is least stable.

Question 9

Which of the following statements about aromaticity is correct?

Accepted Answer

Aromatic compounds must be cyclic, planar, and have (4n+2) $$\pi$$ electrons.

Question 10

Which intermediate is formed when benzene reacts with bromine in the presence of FeBr$$_3$$?

Accepted Answer

A sigma complex (arenium ion)

Question 11

In a Diels-Alder reaction, which of the following factors increases the rate of reaction?

Accepted Answer

Electron-withdrawing groups on the dienophile

Question 12

Which of the following reagents would convert benzene to benzoic acid?

Accepted Answer

$$\text{KMnO}_4$$

Question 13

Which of the following is the correct order of reactivity for electrophilic aromatic substitution (EAS) for the following substituents: $$\text{NO}_2$$, $$\text{OCH}_3$$, $$\text{Cl}$$, $$\text{NH}_2$$?

Accepted Answer

$$\text{NO}_2 \u003c \text{Cl} \u003c \text{OCH}_3 \u003c \text{NH}_2$$

Question 14

Which of the following compounds will show a strong absorption near $$1700 \text{cm}^{-1} in $$its IR spectrum?

Accepted Answer

Benzaldehyde

Question 15

Which of the following is the best explanation for the faster rate of Grignard addition to cyclopentanone compared to cyclohexanone?

Accepted Answer

Cyclopentanone is less sterically hindered than cyclohexanone.

Question 16

Which of the following is the correct set of starting materials for the intramolecular Diels-Alder reaction that produces the following bicyclic product?

Accepted Answer

A diene and a dienophile tethered by a single carbon chain

Question 17

Which of the following reagents would best convert a methylbenzene to benzoic acid?

Accepted Answer

$$\text{KMnO}_4$$

Question 18

Which of the following is the major product when 1,3-butadiene reacts with HBr at $$-78^\circC$$?

Accepted Answer

1-bromo-2-butene (kinetic product)

Question 19

Which of the following statements about the IR spectrum of a carboxylic acid is correct?

Accepted Answer

It shows a strong absorption near $$1700 \text{cm}^{-1}$$ and a broad absorption near $$3000 \text{cm}^{-1}.$$

Organic Chemistry Exam Study Guide: Aromaticity, Acidity, Diels-Alder, and Reaction Mechanisms

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