Question 1

Which of the following best describes the role of sodium borohydride ($$\mathrm{$$NaBH_4$$}) in $$the reduction of aldehydes and ketones?

Accepted Answer

It provides a hydride ion ($$\mathrm{H^-}) $$that acts as a nucleophile, attacking the electrophilic carbonyl carbon.

Question 2

In the context of organic redox reactions, which of the following transformations is classified as a reduction?

Accepted Answer

$$\mathrm{C-Br} to$$ $$\mathrm{C-H}$$

Question 3

How many molecules of an aldehyde or ketone can be reduced by one molecule of $$\mathrm{$$NaBH_4$$}$$?

Accepted Answer

Four

Question 4

Which statement best explains why nucleophilic addition to a carbonyl with an $$\alpha-$$chiral center can lead to diastereomers?

Accepted Answer

The $$\alpha-$$chiral center makes the two faces of the carbonyl diastereotopic, so nucleophilic attack leads to diastereomers.

Question 5

According to the Felkin-Anh model, which group should be oriented perpendicular to the carbonyl plane to predict the major product of nucleophilic addition?

Accepted Answer

The largest group

Question 6

Why is the hydride reduction of benzoin with $$\mathrm{$$NaBH_4$$}$$ considered to be under kinetic control?

Accepted Answer

Because the product ratio is determined by the fastest reaction pathway, not by product stability.

Question 7

Which of the following best describes the Bürgi-Dunitz trajectory in nucleophilic addition to a carbonyl?

Accepted Answer

The nucleophile attacks the carbonyl carbon at an oblique angle (~100°) with respect to the C=O axis.

Question 8

Which laboratory technique is most appropriate for isolating the solid product after a $$\mathrm{$$NaBH_4$$}$$ reduction?

Accepted Answer

Vacuum (suction) filtration

Question 9

What is the main difference between organic and inorganic redox reactions as discussed in the materials?

Accepted Answer

Inorganic redox reactions involve actual electron transfer, while organic redox reactions often involve changes in bond polarity and electron density.

Question 10

Which of the following is NOT a type of reaction commonly encountered in organic chemistry?

Accepted Answer

Precipitation

Question 11

In the reduction of a ketone with $$\mathrm{$$NaBH_4$$}$$, which atom in the product alcohol is derived from the hydride source?

Accepted Answer

The hydrogen atom bonded to the carbon (formerly the carbonyl carbon)

Question 12

Which of the following statements about diastereoselectivity in the $$\mathrm{$$NaBH_4$$}$$ reduction of (+/-)-benzoin is correct?

Accepted Answer

Only one diastereomer is formed after purification due to diastereoselectivity.

Question 13

Which of the following best describes the concept of 'facial topicity' in carbonyl chemistry?

Accepted Answer

It refers to the equivalence or non-equivalence of the two faces of a planar carbonyl group.

Question 14

Which of the following is a correct balanced equation for the reduction of four molecules of a ketone ($$\mathrm{R_2C=O}) $$with one molecule of $$\mathrm{$$NaBH_4$$}$$ and four molecules of water?

Accepted Answer

$$\mathrm{4\ R_2C=O + $$NaBH_4$$ + 4\ H_2O \rightarrow 4\ R_2CHOH + NaB(OH)_4}$$

Question 15

Which of the following is NOT an assumption of the Felkin-Anh model?

Accepted Answer

Product stability determines the major product.

Diastereoselective Hydride Reduction of Benzoin: Mechanism, Stereochemistry, and the Felkin-Anh Model

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