Q: In IR spectroscopy, which of the following is the most likely wavenumber range for the C=O stretching frequency of a simple, unconjugated ketone?

$$1680\ \text{cm}^{-1} to$$ $$1700\ \text{cm}^{-1}$$

Question 1

Which of the following statements best describes the bonding and structure of the carbonyl group in aldehydes and ketones?

Accepted Answer

The carbonyl carbon is sp$$^2$$ hybridized, and the bond angle is approximately 120°.

Question 2

Which of the following compounds is correctly matched with its common name?

Accepted Answer

CH$$_3$$COCH$$_3$$: Acetone

Question 3

Which of the following best explains why aldehydes generally have higher boiling points than alkanes of similar molecular weight, but lower than alcohols?

Accepted Answer

Aldehydes have a polar C=O bond, leading to dipole-dipole interactions, but cannot hydrogen bond with themselves.

Question 4

In IR spectroscopy, which of the following is the most likely wavenumber range for the C=O stretching frequency of a simple, unconjugated ketone?

Accepted Answer

$$1680\ 	ext{cm}^{-1} to$$ $$1700\ 	ext{cm}^{-1}$$

Question 5

Which of the following reactions would best synthesize benzophenone?

Accepted Answer

Friedel-Crafts acylation of benzene with benzoyl chloride

Question 6

Which reagent would selectively reduce an acid chloride to an aldehyde without further reduction to a primary alcohol?

Accepted Answer

DIBAL-H (at low temperature)

Question 7

A student wants to synthesize a ketone from a nitrile. Which sequence of reagents should they use?

Accepted Answer

Grignard reagent followed by hydrolysis

Question 8

Which of the following statements about the McLafferty rearrangement in mass spectrometry is correct?

Accepted Answer

It is a common fragmentation for aldehydes and ketones with a gamma hydrogen.

Question 9

Which of the following best describes the product when acetone reacts with HCN?

Accepted Answer

A cyanohydrin with the structure $$\mathrm{(CH_3$)_2C(OH)CN}$$

Question 10

Which of the following is required to convert an aldehyde to a primary alcohol?

Accepted Answer

NaBH$$_4 in $$methanol

Question 11

Which of the following best explains why ketones are generally resistant to oxidation under normal laboratory conditions?

Accepted Answer

Ketones lack a hydrogen atom on the carbonyl carbon.

Question 12

Which of the following is the correct IUPAC name for the compound with the structure $$\mathrm{CH_3CH_2COCH_3}$$?

Accepted Answer

2-Butanone

Question 13

Which of the following statements about acetal formation is correct?

Accepted Answer

Acetals are formed by reacting an aldehyde or ketone with two equivalents of alcohol under acidic conditions.

Question 14

Which of the following best describes the Wittig reaction?

Accepted Answer

It converts a carbonyl group into an alkene using a phosphorus ylide.

Question 15

Which of the following is the product of the Clemmensen reduction of acetophenone ($$\mathrm{C_6H_5COCH_3}$$)?

Accepted Answer

$$\mathrm{C_6H_5CH_2CH_3}$$

Question 16

A carbohydrate ring structure contains a carbon bonded to both an -OH and an -OR group. What is this carbon classified as?

Accepted Answer

A hemiacetal carbon

Question 17

Which of the following is a Schiff base?

Accepted Answer

An imine formed from the reaction of a primary amine with an aldehyde or ketone

Question 18

Which of the following best describes the product of the reaction between benzaldehyde and hydroxylamine?

Accepted Answer

An oxime

Question 19

Which of the following is true regarding the Tollens test?

Accepted Answer

It is used to distinguish aldehydes from ketones by oxidizing aldehydes to carboxylic acids.

Question 20

Which of the following best describes the effect of conjugation on the IR C=O stretching frequency of an aldehyde or ketone?

Accepted Answer

Conjugation lowers the C=O stretching frequency.

Aldehydes and Ketones: Structure, Properties, Synthesis, and Reactions (Chapter 18 Study Guide)

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