Sulfur Analogs of Alcohols and Ethers

Sulfur is located directly below oxygen in the periodic table, and therefore one might expect the sulfur analogs of alcohols and ethers to behave in a rather similar manner. In this section, we shall see whether this assumption is true. 

The sulfur analogs of alcohols and ethers are thiols and sulfides 

The sulfur analogs of ethers (common name, thioethers) are called sulfides, as in alkyl ether nomenclature. The RS group is named alkylthio, the RS group alkanethiolate. 

Ethyl methyl sulfide 1,1-DimethylethyI 2-Methyltliioethanol Methanethiolate ion 

Thiols are less hydrogen bonded and more acidic than alcohols 

---

Thiols (R—S—H) and sulfides (R—S—R ) are sulfur analogs of alcohols and ethers, respectively. Both functional groups are found in various biomolecules, although not as commonly as their oxygen-containing relatives. 

Sulfur occurs directly beneath oxygen in the periodic table, and, like oxygen, it often exhibits a valence of two. Therefore, sulfur analogs of alcohols and ethers are often encountered. However, because sulfur is in the third period of the periodic table, it can also have a higher valence. Structures with four or six bonds to a sulfur are common. In organic chemistry the most important of these expanded valence compounds have the sulfur bonded to one or two extra oxygens. 

Mercaptans and alkyl sulfides are the sulfur analogs of alcohols and ethers, respectively. They can be characterized by their extremely unpleasant odor. These compounds play an important role in biological systems as well as in the application of chemistry to everyday life. Some of the alkyl sulfides are found in many plant and animal oils, and are minor components of petroleum distillates, shale oil, and coal tar. 

Sulfur analogs of alcohols and ethers are thiols or mercaptanes and sulfides, respectively. According to the nomenclature rules, thiols are named following the same rules as for alcohols, the only difference being that the suffix -ol is replaced with -thiol. Most of these substances can be recognized by their unpleasant odor. Ethanethiol is used as an additive to natural gas since its odor serves as an indicator of a gas leak in home installations. Pure natural gas is odorless. Some animals such as skunks release an unpleasant odor which originates from thiols shown in the next scheme. However, some thiols have a pleasant odor, for instance the components of the aroma of coffee. 

Haloalkanes also undergo nucleophilic substitution reactions with sulfur-containing nucleophiles such as hydrogen sulfide ion (HS ) and thiolate ions (RS"). These reactions yield sulfur analogs of alcohols and ethers namely, thiols and thioethers. 

Thiols, R-SH, are sulfur analogs of alcohols, and sulfides, RSR, are sulfur analogs of ethers. Thiols are named by the same system used for alcohols, with the suffix used in place of-oLThe -SH group itself is referred... 

Sulfides are the sulfur analogs of ethers just as thiols are the sulfur analogs of alcohols. Sulfides are named by following the same rules used for ethers, with sulfide used in place of ether for simple compounds and alkylthio used in place of alkoxy for more complex substances. 

Thiols, the sulfur analogs of alcohols, are usually prepared by Sjv 2 reaction of an alkyl halide with thiourea. Mild oxidation of a thiol yields a disulfide, and mild reduction of a disulfide gives back the thiol. Sulfides, the sulfur analogs of ethers, are prepared by an Sk2 reaction between a thiolate anion and a primary or secondary alkyl halide. Sulfides are much more nucleophilic than ethers and can be oxidized to sulfoxides and to sulfones. Sulfides can also be alkylated by reaction with a primary alkyl halide to yield sulfonium ions. 

A characteristic of organic sulfur compounds, especially volatile (low molecular mass) thiols, is their disagreeable odors. For example, 3-methyl-1-butanethiol and 2-butene-1-thiol are ingredients of a skunk s perfume, and methanethiol or ethanethiol is usually added, in small amounts, to natural gas, which is odorless by itself, so that leaks can be readily detected. The chemical properties of thiols and sulfides differ from those of alcohols and ethers in that thiols are somewhat stronger acids than alcohols and the sulfur atoms of these compounds are considerably more nucleophilic than the oxygen of their analogs. They are excellent nucleophiles in substitution reactions. 

Thiols are sulfur analogs of alcohols. They are stronger acids and have lower boiling points than alcohols. Thiolate ions are weaker bases and better nucleophiles in protic solvents than alkoxide ions. Sulfur analogs of ethers are called sulfides or thioethers. Sulfides react with alkyl halides to form sulfonium salts. 

Sulfides (RSR ) are the sulfur analogs of ethers Just as m the preceding chapter where we saw that the properties of thiols (RSH) are different from those of alcohols we will explore differences between sulfides and ethers m this chapter... 

---