Q: Which IR spectrum would you expect for 3-hexanone based on the provided images?

A strong absorption near $$\text{1715 cm$$^{-1}$$}$$ and no aldehyde C-H stretch

Question 1

Which IR absorption is most characteristic for the C=O stretch in an aliphatic aldehyde, such as acetaldehyde?

Accepted Answer

$$	ext{1730 cm$$^{-1}$$}$$

Question 2

In the mechanism of imine formation from an aldehyde and a primary amine, which intermediate is formed before water is eliminated?

Accepted Answer

A tetrahedral intermediate

Question 3

Why does imine formation proceed best under weakly acidic conditions (pH ≈ 4.5)?

Accepted Answer

Because strong acid protonates the amine, reducing its nucleophilicity

Question 4

Which of the following is NOT an imine derivative?

Accepted Answer

Enamine

Question 5

The Wolff-Kishner reaction is used for which transformation?

Accepted Answer

Deoxygenation of aldehydes and ketones to hydrocarbons

Question 6

Which reagent gives a 1,4-conjugate addition product with $$\alpha,\beta-$$unsaturated ketones?

Accepted Answer

Organocuprate (Gilman reagent)

Question 7

Why are acetals used as protecting groups for aldehydes and ketones?

Accepted Answer

Because acetals are inert to hydride reducing agents

Question 8

Which of the following statements about the Wittig reaction is TRUE?

Accepted Answer

It converts aldehydes and ketones to alkenes using a phosphorous ylide

Question 9

Which type of alkyl halide is NOT suitable for ylide formation in the Wittig reaction?

Accepted Answer

Tertiary alkyl halide

Question 10

In IR spectroscopy, which absorption is diagnostic for an aromatic aldehyde such as benzaldehyde?

Accepted Answer

$$	ext{1705 cm$$^{-1}$$}$$

Question 11

Which NMR chemical shift is diagnostic for the aldehyde proton in propanal?

Accepted Answer

$$\delta \approx 10.0$$

Question 12

Which mass spectrometry fragmentation is characteristic for aldehydes and ketones with gamma hydrogens?

Accepted Answer

McLafferty rearrangement

Question 13

Which IR spectrum would you expect for 3-hexanone based on the provided images?

Accepted Answer

A strong absorption near $$	ext{1715 cm$$^{-1}$$}$$ and no aldehyde C-H stretch

Question 14

Which of the following carbonyl types has the highest IR absorption frequency?

Accepted Answer

4-membered ring ketone

Question 15

Which NMR chemical shift range is typical for protons adjacent to a carbonyl group in aldehydes and ketones?

Accepted Answer

$$\delta = 2.0 - 2.3$$

Question 16

Which of the following is TRUE about the conjugate addition of amines to $$\alpha,\beta-$$unsaturated carbonyl compounds?

Accepted Answer

Both primary and secondary amines add by 1,4-addition to give $$\beta-$$amino aldehydes and ketones

Question 17

Which spectroscopic technique would you use to distinguish between saturated and $$\alpha,\beta-$$unsaturated aldehydes and ketones based on their UV activity?

Accepted Answer

UV spectroscopy

Question 18

Which mass spectrometry fragmentation pattern is shown in the image with the label 'Alpha cleavage'?

Accepted Answer

Cleavage of the bond adjacent to the carbonyl group, forming a radical and a cation

Question 19

Which of the following statements about acetal formation is TRUE?

Accepted Answer

Acetal formation is reversible and favored by removal of water from the reaction mixture

Reactivity and Spectroscopy of Aldehydes and Ketones

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