Question 1

Which of the following best describes the hybridization and bonding in the carbonyl group ($$C=O) of $$aldehydes and ketones?

Accepted Answer

The carbon is $$sp^2-$$hybridized, forming one $$\sigma-$$bond (from $$sp^2$$ orbitals) and one $$\pi-$$bond (from parallel $$2p$$ orbitals) with oxygen.

Question 2

The molecule shown in the first image is an example of which functional group?

Accepted Answer

Aldehyde

Question 3

Which of the following is the correct IUPAC name for the compound with the structure $$CH_3CH_2CHO$$?

Accepted Answer

Propanal

Question 4

In the $$^1H$$ NMR spectrum of propanal (see image 4), which signal corresponds to the aldehydic proton?

Accepted Answer

The signal at $$\sim 9.5$$ ppm

Question 5

Which of the following statements about the nucleophilic addition to carbonyl compounds is correct?

Accepted Answer

Nucleophilic addition to the carbonyl carbon results in a tetrahedral intermediate.

Question 6

Which of the following best explains why halide ions (e.g., $$Cl^-) $$are ineffective nucleophiles in nucleophilic addition to carbonyls?

Accepted Answer

$$Cl^- is a $$much weaker base than the alkoxide formed, so equilibrium favors the starting materials.

Question 7

Which of the following is a product of the reaction between an aldehyde and hydrogen cyanide ($$HCN$$)?

Accepted Answer

A cyanohydrin

Question 8

The Wittig reaction is used to convert a carbonyl group into which of the following?

Accepted Answer

An alkene

Question 9

Which of the following is true about the product(s) of the Wittig reaction?

Accepted Answer

It always gives a single constitutional isomer with a known double bond location.

Question 10

Which of the following best describes the mechanism of imine (Schiff base) formation from an aldehyde and a primary amine?

Accepted Answer

Nucleophilic addition of the amine to the carbonyl, followed by elimination of water.

Question 11

Which of the following statements about the hydration of aldehydes and ketones is correct?

Accepted Answer

Increasing the number of alkyl groups on the carbonyl carbon decreases the amount of hydrate at equilibrium.

Question 12

Which of the following is a correct statement about acetals?

Accepted Answer

Acetals are formed by the acid-catalyzed addition of two equivalents of alcohol to an aldehyde or ketone.

Question 13

Which of the following is a practical use of acetals in organic synthesis?

Accepted Answer

They are used as protecting groups for aldehydes and ketones.

Question 14

Which of the following best describes the product formed when a secondary amine reacts with a ketone?

Accepted Answer

An enamine

Question 15

Which of the following is a correct statement about the hydrolysis of acetals?

Accepted Answer

Acetals can be hydrolyzed back to aldehydes or ketones by treatment with aqueous acid.

Question 16

Which of the following is a stable compound formed by the intramolecular cyclization of a hydroxy aldehyde?

Accepted Answer

A cyclic hemiacetal (lactol)

Question 17

Which of the following best explains why imine formation is fastest under mildly acidic conditions?

Accepted Answer

Acid catalysis increases the electrophilicity of the carbonyl carbon, facilitating nucleophilic attack by the amine.

Question 18

Which of the following is a correct statement about the $$^{13}C$$ NMR spectrum of propanal (see image 5)?

Accepted Answer

The carbonyl carbon appears at $$\sim 200$$ ppm.

Question 19

Which of the following is a real-world application of the chemistry of imines?

Accepted Answer

The formation of rhodopsin in the rod cells of the eye, which is essential for vision.

Aldehydes and Ketones: Nucleophilic Addition and Properties

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