Question 1

Which of the following statements best explains why ethers and sulfides are considered weak bases?

Accepted Answer

They can accept a proton to form conjugate acid cations, but their conjugate acids are less stable than those of strong bases.

Question 2

In the Williamson ether synthesis, which combination of alkyl halide and alkoxide would give the highest yield of tert-butyl methyl ether?

Accepted Answer

methyl bromide and sodium tert-butoxide

Question 3

Which reagent is used in the alkoxymercuration-reduction of alkenes to form ethers?

Accepted Answer

$$\mathrm{Hg(OAc)_2}$$, $$\mathrm{ROH}$$, followed by $$\mathrm{$$NaBH_4$$}$$

Question 4

Why is the dehydration of alcohols to form ethers generally restricted to primary alcohols?

Accepted Answer

Secondary and tertiary alcohols undergo elimination to form alkenes under the required harsh conditions.

Question 5

Which of the following best describes the mechanism of ether formation from alcohol dehydration?

Accepted Answer

It is an $$\mathrm{S_N2}$$ reaction involving nucleophilic attack by alcohol on a protonated alcohol.

Question 6

Which reagent is commonly used to oxidize alkenes directly to epoxides?

Accepted Answer

Peroxycarboxylic acids such as $$\mathrm{mCPBA}$$

Question 7

Epoxidation of alkenes with peroxycarboxylic acids is stereospecific. What is the stereochemical outcome when trans-stilbene is treated with $$\mathrm{mCPBA}$$?

Accepted Answer

A racemic mixture of enantiomers is formed.

Question 8

Which statement correctly describes the regioselectivity of epoxide ring-opening under basic conditions?

Accepted Answer

The nucleophile attacks the less hindered (less substituted) carbon of the epoxide.

Question 9

What is the major product when 2,2-dimethyloxirane (isobutylene oxide) is treated with methanol and $$\mathrm{H_2SO_4} ($$acidic conditions)?

Accepted Answer

2-methoxy-2-methyl-1-propanol

Question 10

Which of the following best explains the difference in regioselectivity of epoxide ring-opening under acidic versus basic conditions?

Accepted Answer

Under acidic conditions, the nucleophile attacks the more substituted carbon due to carbocation-like character.

Question 11

Which reagent is used for the oxidative cleavage of glycols to aldehydes and ketones?

Accepted Answer

$$\mathrm{H_5IO_6} ($$periodic acid)

Question 12

What is the role of ethers as Lewis bases in the complexation with $$\mathrm{BF_3$}$$?

Accepted Answer

Ethers donate a lone pair of electrons to $$\mathrm{BF_3$}$$, stabilizing the complex.

Question 13

Which of the following is true about the reaction of Grignard reagents with epoxides?

Accepted Answer

The reaction extends the carbon chain by two carbons and forms a primary alcohol after workup.

Question 14

Which statement best describes the stereochemistry of glycol formation from alkenes using $$\mathrm{$$OsO_4$$}$$?

Accepted Answer

The addition of two OH groups is syn, leading to cis diols.

Question 15

Which of the following is a correct statement about the cleavage of ethers with tertiary alkyl groups?

Accepted Answer

Cleavage occurs under milder conditions and involves a carbocation intermediate ($$\mathrm{S_N1}$$ mechanism).

Question 16

Which of the following is true about the reactivity of oxonium and sulfonium salts?

Accepted Answer

They react with nucleophiles in $$\mathrm{S_N2}$$ reactions and are highly reactive alkylating agents.

Question 17

Which statement best explains why intramolecular reactions are generally faster than intermolecular reactions?

Accepted Answer

Intramolecular reactions have lower activation energy due to proximity of reactant groups.

Question 18

What is the major product when cyclopentene is treated with $$\mathrm{$$KMnO_4$$}$$ and water?

Accepted Answer

cis-1,2-cyclopentanediol

Question 19

Which of the following is a correct statement about the reaction of lithium organocuprate reagents with epoxides?

Accepted Answer

The reaction proceeds via an $$\mathrm{S_N2}$$ mechanism at the less substituted carbon.

Chapter 12: The Chemistry of Ethers, Epoxides, Glycols, and Sulfides – Study Notes

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