Question 1

Which of the following statements best describes the difference between oxidation and reduction in organic chemistry?

Accepted Answer

Oxidation is the removal of hydrogens and addition of oxygens, while reduction is the addition of hydrogens and removal of oxygens.

Question 2

Which reagent would you use to reduce a ketone to a secondary alcohol?

Accepted Answer

$$\mathrm{$$NaBH_4$$} ($$sodium borohydride)

Question 3

What is the role of the proton source in the reduction of a carbonyl compound with $$\mathrm{$$NaBH_4$$}$$?

Accepted Answer

It protonates the alkoxide intermediate to yield the alcohol.

Question 4

Which of the following statements about the mechanism of $$\mathrm{$$NaBH_4$$}$$ reduction of aldehydes is correct?

Accepted Answer

Hydride and proton are added simultaneously in a concerted mechanism.

Question 5

Why can't tertiary alcohols be synthesized by direct reduction of ketones or aldehydes using $$\mathrm{$$NaBH_4$$} or$$ $$\mathrm{$$LiAlH_4$$}$$?

Accepted Answer

Ketones and aldehydes do not have enough carbon atoms to form tertiary alcohols by simple reduction.

Question 6

Which of the following best describes the function of a Grignard reagent ($$\mathrm{RMgX}) in $$organic synthesis?

Accepted Answer

It acts as a nucleophile, forming new C–C bonds with carbonyl compounds.

Question 7

In the reaction of a Grignard reagent with a ketone followed by aqueous work-up, what is the major organic product?

Accepted Answer

A tertiary alcohol

Question 8

Which of the following is a limitation of using $$\mathrm{$$NaBH_4$$}$$ and $$\mathrm{$$LiAlH_4$$}$$ for alcohol synthesis?

Accepted Answer

They cannot increase the number of carbon atoms in the product.

Question 9

Which of the following statements about ethers is correct?

Accepted Answer

Ethers are aprotic polar solvents with relatively low boiling points.

Question 10

In the Williamson ether synthesis, why is it preferable to use a primary alkyl halide?

Accepted Answer

Primary alkyl halides are less likely to undergo elimination reactions.

Question 11

Which of the following best explains the regioselectivity observed in the basic ring-opening of an epoxide?

Accepted Answer

The nucleophile attacks the less hindered (less substituted) carbon via an $$\mathrm{S_N2}$$ mechanism.

Question 12

In $$^1H $$NMR spectroscopy, what does the area under a peak represent?

Accepted Answer

The number of protons (hydrogens) contributing to that signal.

Question 13

What is the effect of an electronegative atom (such as Cl) attached to a carbon on the chemical shift of nearby hydrogens in $$^1H $$NMR?

Accepted Answer

It causes deshielding, moving the peak downfield (higher ppm).

Question 14

According to the N+1 rule in $$^1H $$NMR, how many peaks would you expect for a hydrogen atom with two equivalent neighboring hydrogens?

Accepted Answer

Three peaks (a triplet)

Question 15

Which of the following is true regarding the chemical shift $$\delta in $$NMR spectroscopy?

Accepted Answer

$$\delta is $$measured relative to tetramethylsilane (TMS) as an internal standard.

Question 16

Which of the following best describes the splitting pattern for the methyl group in ethanol ($$\mathrm{CH_3CH_2OH}) in $$its $$^1H $$NMR spectrum?

Accepted Answer

A triplet

Question 17

Which of the following is a correct statement about the mechanism of $$\mathrm{$$PBr_3$$}$$ reaction with alcohols?

Accepted Answer

The reaction involves conversion of the alcohol to a good leaving group, followed by $$\mathrm{S_N2}$$ displacement.

Question 18

Which of the following is NOT a property of ethers?

Accepted Answer

They are highly reactive toward most nucleophiles under neutral conditions.

Question 19

In the acid-catalyzed ring opening of an unsymmetrical epoxide, which carbon does the nucleophile preferentially attack?

Accepted Answer

The more substituted carbon due to electronic effects

Alcohols, Ethers, and NMR Spectroscopy: Structure, Synthesis, and Reactions

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