Question

Show how the following ethers might be synthesized using (1) alkoxymercuration-demercuration and (2) the Williamson synthesis. (When one of these methods cannot be used for the given ether, point out why it will not work.)

1. 2-methoxybutane
2. Ethyl cyclohexyl ether
3. 1-methoxy-2-methylcyclopentane
4. 1-methoxy-1-methylcyclopentane
5. 1-isopropoxy-1-methylcyclopentane
6. Tert-butyl phenyl ether

Short answer

Alkoxymercuration-dermercuration is a reaction in which an alkene reacts with an alcohol in the presence of mercuric acetate to form an alkoxymercury intermediate which is then reduced with sodium borohydride to produce an ether.

Williamson ether synthesis is a ${\mathbf{S}}_{\mathbf{N}}^{}\mathbf{2}$reaction in which an alkoxide ion is a nucleophile that displaces a halide ion from an alkyl halide to give ether.

In part (a), preparation of 2-methoxybutane takes place from alkoxymercuration-demercuration and Williamson ether synthesis. (1) indicates alkoxymercuration-demercuration mechanism while (2) indicates Williamson ether synthesis.

Step-by-step solution

Step-1. Explanation of part (a):

Alkoxymercuration-dermercuration is a reaction in which an alkene reacts with an alcohol in the presence of mercuric acetate to form an alkoxymercury intermediate which is then reduced with sodium borohydride to produce an ether.

Williamson ether synthesis is a ${\mathbf{S}}_{\mathbf{N}}^{}\mathbf{2}$reaction in which an alkoxide ion is a nucleophile that displaces a halide ion from an alkyl halide to give ether.

In part (a), preparation of 2-methoxybutane takes place from alkoxymercuration-demercuration and Williamson ether synthesis. (1) indicates alkoxymercuration-demercuration mechanism while (2) indicates Williamson ether synthesis.

Step-2. Explanation of part (b):

Alkoxymercuration-dermercurationis a reaction in which an alkene reacts with an alcohol in the presence of mercuric acetate to form an alkoxymercury intermediate which is then reduced with sodium borohydride to produce ether.

Williamson ether synthesis is a ${\mathbf{S}}_{\mathbf{N}}\mathbf{2}$reaction in which an alkoxide ion is a nucleophile that displaces a halide ion from an alkyl halide to give an ether.

In part (b), preparation of ethoxycyclohexane takes place from alkoxymercuration-demercuration and Williamson ether synthesis. (1) indicates alkoxymercuration-demercuration mechanism while (2) indicates Williamson ether synthesis.

Step-3. Explanation of part (c):

Alkoxymercuration-dermercurationis a reaction in which an alkene reacts with an alcohol in the presence of mercuric acetate to form an alkoxymercury intermediate which is then reduced with sodium borohydride to produce ether.

Williamson ether synthesis is a ${\mathbf{S}}_{\mathbf{N}}\mathbf{2}$reaction in which an alkoxide ion is a nucleophile that displaces a halide ion from an alkyl halide to give ether.

In part (c), preparation of 1-methoxy-2-methylcyclopentane takes place from Williamson ether synthesis. Alkoxymercuration is not practical here, the product does not have Markovnikov orientation required for alkoxymercuration-demercuration. (2) indicates Williamson ether synthesis.

Step-4. Explanation of part (d):

Alkoxymercuration-dermercurationis a reaction in which an alkene reacts with an alcohol in the presence of mercuric acetate to form an alkoxymercury intermediate which is then reduced with sodium borohydride to produce ether.

Williamson ether synthesis is a ${\mathbf{S}}_{\mathbf{N}}\mathbf{2}$reaction in which an alkoxide ion is a nucleophile that displaces a halide ion from an alkyl halide to give ether.

In part (d), preparation of 1-methoxy-1-methylcyclopentane takes place from alkoxymercuration-demercuration and Williamson ether synthesis. (1) indicates alkoxymercuration-demercuration mechanism while (2) indicates Williamson ether synthesis.

Preparation of the product

Step-5. Explanation of part (e):

Alkoxymercuration-dermercurationis a reaction in which an alkene reacts with an alcohol in the presence of mercuric acetate to form an alkoxymercury intermediate which is then reduced with sodium borohydride to produce ether.

Williamson ether synthesis is a ${\mathbf{S}}_{\mathbf{N}}\mathbf{2}$reaction in which an alkoxide ion is a nucleophile that displaces a halide ion from an alkyl halide to give ether.

In part (e), preparation of 1-isopropoxy-1-methylcyclopentane takes place from alkoxymercuration-demercuration only. Williamson ether synthesis would give a poor yield of product as halide is on a secondary carbon. (1) indicates alkoxymercuration-demercuration mechanism.

Preparation of the product

Step-6. Explanation of part (f):

Alkoxymercuration-dermercurationis a reaction in which an alkene reacts with an alcohol in the presence of mercuric acetate to form an alkoxymercury intermediate which is then reduced with sodium borohydride to produce ether.

Williamson ether synthesis is a ${\mathbf{S}}_{\mathbf{N}}\mathbf{2}$reaction in which an alkoxide ion is a nucleophile that displaces a halide ion from an alkyl halide to give ether.

In part (f), preparation of tert-butoxybenzene takes place from alkoxymercuration-demercuration. Williamson ether synthesis is not feasible because mechanism is not possible with tertiary halides or halobenzene. (1) indicates alkoxymercuration-demercuration mechanism .