Question 1

Which of the following statements best describes the role of organometallic reagents such as Grignard and organolithium compounds in organic synthesis?

Accepted Answer

They serve as strong nucleophiles, attacking electrophilic carbon atoms such as those in carbonyl groups.

Question 2

A chemist wants to prepare a tertiary alcohol by reacting a ketone with an organometallic reagent. Which combination would be most effective?

Accepted Answer

Reacting acetone with $$\mathrm{CH_3MgBr}$$ followed by $$\mathrm{H_2O}$$ workup.

Question 3

Which of the following is a key difference between Grignard reagents ($$\mathrm{RMgX}) $$and organolithium reagents ($$\mathrm{RLi}$$)?

Accepted Answer

Grignard reagents are generally less reactive and more selective than organolithium reagents.

Question 4

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

Accepted Answer

They react rapidly with water to form alkanes and destroy the reagent.

Question 5

A student attempts to prepare a Grignard reagent from bromobenzene and magnesium in ether. Which of the following would prevent successful formation of the Grignard reagent?

Accepted Answer

Presence of water in the reaction mixture.

Question 6

Which of the following reactions is an example of the Heck coupling reaction?

Accepted Answer

Coupling of an aryl halide with an alkene in the presence of $$\mathrm{Pd(OAc)_2}$$ and $$\mathrm{Et_3N}.$$

Question 7

In the Suzuki reaction, which of the following is a required reagent for the coupling of an aryl halide with an organoboron compound?

Accepted Answer

$$\mathrm{Pd($$PPh_3$$)_4}$$

Question 8

Which of the following statements about the Stille coupling reaction is correct?

Accepted Answer

It uses an organotin reagent and a palladium catalyst to form a new C–C bond.

Question 9

A chemist wants to synthesize 1-phenyl-1-butene using a Heck reaction. Which starting materials should be used?

Accepted Answer

Bromobenzene and 1-butene with $$\mathrm{Pd(OAc)_2}$$ catalyst.

Question 10

Which of the following best describes the product of the reaction between cyclohexanone and $$\mathrm{CH_3Li}$$ followed by aqueous workup?

Accepted Answer

A tertiary alcohol with a methyl group added to the carbonyl carbon.

Question 11

Which reagent would be most suitable for reducing an ester to a primary alcohol?

Accepted Answer

$$\mathrm{$$LiAlH_4$$}$$

Question 12

In the preparation of Gilman reagents ($$\mathrm{R_2CuLi}$$), which of the following is a necessary step?

Accepted Answer

Reacting an organolithium compound with $$\mathrm{CuI}.$$

Question 13

Which of the following statements about the reactivity of lithium reagents compared to Grignard reagents is correct?

Accepted Answer

Lithium reagents are generally more reactive and can be used to prepare sterically hindered alcohols.

Question 14

Which of the following is a key feature of the olefin metathesis reaction catalyzed by Grubbs catalyst?

Accepted Answer

It involves the exchange of alkylidene groups between alkenes, forming new C=C bonds.

Question 15

A chemist performs a ring-closing metathesis on 1,6-heptadiene using Grubbs catalyst. What is the expected product?

Accepted Answer

Cyclohexene

Question 16

Which of the following best describes the mechanism of the cyclopropanation reaction using $$\mathrm{CH_2I_2}$$ and $$\mathrm{Zn(Cu)}$$?

Accepted Answer

Formation of a carbene intermediate that adds to the double bond to form a cyclopropane ring.

Question 17

Which of the following is a common application of the Suzuki coupling reaction in pharmaceutical synthesis?

Accepted Answer

Formation of biaryl structures for drug molecules.

Question 18

Which of the following is a plausible reason for using Gilman reagents ($$\mathrm{R_2CuLi}) $$instead of Grignard reagents in certain coupling reactions?

Accepted Answer

Gilman reagents are less reactive and more selective, allowing coupling with alkyl halides without side reactions.

Question 19

Which of the following best describes the outcome when $$\mathrm{$$NaBH_4$$} is $$used to reduce a ketone?

Accepted Answer

A secondary alcohol is formed.

Organometallics and Coupling Reactions: Study Notes for General Chemistry (Organic Focus)

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