Question 1

Which type of reaction is illustrated in all three parts (a, b, and c) of the provided mechanisms?

Accepted Answer

Grignard addition to a carbonyl

Question 2

In reaction (a), what is the role of $$\mathrm{Mg, Et_2O} in $$the first step?

Accepted Answer

It forms a Grignard reagent by inserting Mg into the C–Br bond.

Question 3

What is the major product of the reaction in part (a) after all steps are completed?

Accepted Answer

1-Phenyl-1-ethanol

Question 4

In the mechanism for part (a), what is the function of the epoxide?

Accepted Answer

It acts as an electrophile, being attacked by the Grignard reagent.

Question 5

In part (b), why is excess Grignard reagent used?

Accepted Answer

To react with both carbonyl groups in the dialdehyde substrate.

Question 6

What is the final product of the reaction in part (b) after hydrolysis?

Accepted Answer

A 1,6-diol

Question 7

In part (c), what is the nucleophile in the Grignard addition step?

Accepted Answer

The carbon atom bonded to MgBr in the Grignard reagent

Question 8

Which of the following best describes the mechanism of Grignard addition to a carbonyl group?

Accepted Answer

Nucleophilic addition to the carbonyl carbon, followed by protonation

Question 9

After the Grignard addition in part (c), what is the hybridization of the carbon that was originally the carbonyl carbon?

Accepted Answer

$$sp^3$$

Question 10

Which of the following statements about Grignard reagents is TRUE?

Accepted Answer

They are strong nucleophiles and bases.

Question 11

A student attempts the reaction in part (a) but forgets to dry the ether solvent. What is the most likely outcome?

Accepted Answer

The Grignard reagent is destroyed by water, and no product forms.

Question 12

In the context of pharmaceutical synthesis, why are Grignard reactions important?

Accepted Answer

They allow for the formation of carbon–carbon bonds, enabling the synthesis of complex alcohols.

Question 13

Which of the following best explains why Grignard reagents must be prepared and used under anhydrous conditions?

Accepted Answer

They react with water to form hydrocarbons and lose their nucleophilicity.

Question 14

In part (a), what is the stereochemistry of the product if the epoxide is asymmetric?

Accepted Answer

A racemic mixture of enantiomers is formed.

Question 15

Which of the following is a common side reaction when using Grignard reagents with substrates containing acidic hydrogens?

Accepted Answer

Protonation of the Grignard reagent, forming an alkane

Question 16

A chemist wants to synthesize 2-phenyl-2-butanol using a Grignard reaction. Which combination of starting materials would be appropriate?

Accepted Answer

Phenylmagnesium bromide and 2-butanone

Question 17

In the reaction shown in part (c), what is the function of $$\mathrm{H_2O, H^+} in $$the final step?

Accepted Answer

To protonate the alkoxide intermediate, forming the alcohol

Question 18

Which of the following best describes the regiochemistry of Grignard addition to an epoxide, as in part (a)?

Accepted Answer

The Grignard attacks the less substituted carbon of the epoxide.

Question 19

A student tries to perform the reaction in part (b) with a ketone instead of an aldehyde. What is the expected difference in reactivity?

Accepted Answer

The reaction will proceed slower because ketones are less reactive than aldehydes.

Grignard Reactions: Mechanisms and Products (Chapter 17)

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