Sulfides

Sulfur analogs of ethers are called sulfides. The chemical behavior of sulfides contrasts with that of ethers in some important ways. Since hydrogen sulfide (H₂S) is a much stronger acid than water (by more than ten million fold), we expect, and find, thiols to be stronger acids than equivalent alcohols and phenols. Thiolate conjugate bases are easily formed, and have proven to be excellent nucleophiles in S_N2 reactions of alkyl halides and tosylates.

R–S^(–) Na⁽⁺⁾ + (CH₃)₂CH–Br (CH₃)₂CH–S–R + Na⁽⁺⁾ Br^(–)

Although the basicity of ethers is roughly a hundred times greater than that of equivalent sulfides, the nucleophilicity of sulfur is much greater than that of oxygen, leading to a number of interesting and useful electrophilic substitutions of sulfur that are not normally observed for oxygen. Sulfides, for example, react with alkyl halides to give ternary sulfonium salts (equation # 1) in the same manner that 3º-amines are alkylated to quaternary ammonium salts. Although equivalent oxonium salts of ethers are known, they are only prepared under extreme conditions, and are exceptionally reactive.

sulfides are named using the same rules as ethers except sulfide is used in the place of ether. For more complex substance alkylthio is used instead of alkoxy.