Question 1

Which of the following statements best explains why benzene undergoes substitution reactions rather than addition reactions, despite having three double bonds?

Accepted Answer

Addition reactions would disrupt the aromatic stabilization provided by delocalized $$\pi$$ electrons.

Question 2

A compound with molecular formula $$C_5H_8$$ shows the following IR absorptions: a strong peak at $$1715\ 	ext{cm}^{-1}$$ and no broad O–H stretch. Its $$^1H $$NMR shows a singlet at $$2.2$$ ppm integrating to $$6$$ protons. What is the most likely structure?

Accepted Answer

3-Pentanone

Question 3

Which of the following best describes the product(s) when 1,3-butadiene reacts with HBr at low temperature ($$-78^\circC$$)?

Accepted Answer

The 1,2-addition product is favored due to kinetic control.

Question 4

Which of the following compounds is aromatic according to Hückel’s rule?

Accepted Answer

Cyclopentadienyl anion

Question 5

In the Diels-Alder reaction between 1,3-butadiene and maleic anhydride, which product is favored and why?

Accepted Answer

The endo product is favored due to secondary orbital interactions.

Question 6

Which of the following statements about the $$^{13}C $$NMR spectrum of benzene is correct?

Accepted Answer

It shows one signal because all carbons are equivalent.

Question 7

Which reagent would best convert a primary alcohol to a carboxylic acid?

Accepted Answer

Jones reagent ($$\ce{CrO3} in $$aqueous $$\ce{H2SO4})$$

Question 8

Which of the following is the correct order of reactivity toward nucleophilic acyl substitution (most to least reactive)?

Accepted Answer

Acid chloride \u003e anhydride \u003e ester \u003e amide

Question 9

A student treats acetophenone with bromine in acetic acid. What is the major product?

Accepted Answer

Bromination occurs at the alpha position to the carbonyl group.

Question 10

Which of the following statements about the Claisen condensation is correct?

Accepted Answer

It forms a $$\beta-$$keto ester via enolate attack on an ester.

Question 11

Which of the following best explains why LDA is used to generate kinetic enolates?

Accepted Answer

LDA is a strong, non-nucleophilic base that deprotonates the less hindered $$\alpha-$$proton rapidly at low temperature.

Question 12

Which of the following is a correct statement about the mechanism of electrophilic aromatic substitution (EAS)?

Accepted Answer

The aromatic ring attacks the electrophile, forming a non-aromatic carbocation intermediate.

Question 13

Which of the following is the correct product when benzaldehyde reacts with excess methylmagnesium bromide ($$\ce{CH3MgBr}) $$followed by aqueous workup?

Accepted Answer

1-Phenylethanol

Question 14

Which of the following statements about the formation of acetals from aldehydes is correct?

Accepted Answer

Acetal formation requires acid catalysis and removal of water to drive the reaction to completion.

Question 15

Which of the following best describes the product of the reaction between ethyl acetoacetate and ethyl iodide in the presence of sodium ethoxide?

Accepted Answer

Alkylation at the $$\alpha-$$carbon to give an ethylated $$\beta-$$keto ester.

Question 16

Which of the following is a correct statement about the Mannich reaction?

Accepted Answer

It forms a $$\beta-$$amino carbonyl compound from an enolizable carbonyl, formaldehyde, and an amine.

Question 17

Which of the following statements about the basicity of amines is correct?

Accepted Answer

Amines are less basic than amides because the lone pair on nitrogen in amides is delocalized by resonance.

Question 18

Which of the following is the correct sequence of steps to synthesize aniline from nitrobenzene?

Accepted Answer

Reduction with Sn/HCl

Question 19

Which of the following best describes the product of the reaction of cyclohexanone with hydrazine under basic conditions (Wolff-Kishner reduction)?

Accepted Answer

Cyclohexane

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