Question 1

Which of the following statements best explains why organolithium compounds are highly nucleophilic?

Accepted Answer

The carbon in organolithium compounds is highly carbanionic due to the large difference in electronegativity between carbon and lithium.

Question 2

Given the following reaction: $$\mathrm{CH_3Br + 2Li \rightarrow CH_3Li + LiBr}$$, which solvent would be most appropriate to use and why?

Accepted Answer

An aprotic solvent such as hexane, because organolithium compounds are strongly basic and react with protic solvents.

Question 3

Which organometallic compound would have the most ionic character in its C–M bond based on the provided table?

Accepted Answer

$$\mathrm{CH_3Li}$$

Question 4

Why are ethers such as diethyl ether and tetrahydrofuran (THF) commonly used as solvents in Grignard reactions?

Accepted Answer

They are aprotic and can stabilize the organomagnesium intermediate without reacting with it.

Question 5

Which of the following alkyl halides would react fastest with magnesium to form a Grignard reagent?

Accepted Answer

An alkyl iodide

Question 6

A chemist wants to prepare a nucleophilic carbon species from a terminal alkyne. Which reagent should they use?

Accepted Answer

$$\mathrm{$$NaNH_2$$}$$

Question 7

Which of the following best describes the mechanism for the formation of organolithium compounds from alkyl halides?

Accepted Answer

A three-step process involving radical formation, fragmentation, and recombination with lithium.

Question 8

Why must aprotic solvents be used in the preparation of organometallic compounds such as Grignard reagents?

Accepted Answer

Protic solvents would react with the organometallic compound, destroying its nucleophilicity.

Question 9

Which of the following statements about the reactivity of alkyl halides in forming organometallic compounds is correct?

Accepted Answer

Alkyl iodides are more reactive than alkyl fluorides in forming organolithium and Grignard reagents.

Question 10

A student attempts to prepare a Grignard reagent using $$\mathrm{CH_3Br}$$ and magnesium in water. What is the most likely outcome?

Accepted Answer

The Grignard reagent will not form because water will react with it, destroying its nucleophilicity.

Question 11

Which of the following best explains why organometallic compounds are useful in organic synthesis?

Accepted Answer

They provide a source of nucleophilic carbon for forming new carbon–carbon bonds.

Question 12

Which of the following reactions represents the preparation of a sodium alkynide?

Accepted Answer

$$\mathrm{RC \equiv CH + $$NaNH_2$$ \rightarrow RC \equiv CNa + NH_3$}$$

Question 13

Which of the following organometallic compounds would have the lowest percent ionic character in the C–M bond, based on the table?

Accepted Answer

$$\mathrm{C-Hg}$$

Question 14

A chemist is choosing between diethyl ether and THF as a solvent for a Grignard reaction. Which factor is most relevant to this choice?

Accepted Answer

The boiling point of the solvent, as THF allows higher reaction temperatures for less reactive reagents.

Question 15

Which of the following best describes the role of the sodium ion in sodium alkynide formation?

Accepted Answer

It stabilizes the carbanion formed after deprotonation of the terminal alkyne.

Question 16

Which of the following statements about the mechanism of Grignard reagent formation is correct?

Accepted Answer

It involves a radical intermediate and the combination of the alkyl radical with magnesium.

Question 17

Which of the following best explains why alkyl fluorides are less reactive than alkyl iodides in forming organometallic compounds?

Accepted Answer

The C–F bond is much stronger and harder to break than the C–I bond.

Organometallic Compounds: Structure, Reactivity, and Mechanisms

Study Guide - Practice Questions