Alcohols, Phenols, and Thiols

The functional group of alcohols and phenols is the hydroxyl group. In alcohols, this group is connected to an aliphatic carbon, whereas in phenols, it is attached to an aromatic ring. 

In the IUPAC system of nomenclature, the suffix for alcohols is -ol. Alcohols are classified as primary, secondary, or tertiary depending on whether one, two, or three organic groups are attached to the hydroxyl-bearing carbon. The nomenclature of alcohols and phenols is summarized in Secs. 7.1-7.3. 

Alcohols and phenols form hydrogen bonds. These bonds account for the relatively high boiling points of these substances and the water solubility of lower members of the series. 

Bronsted-Lowry and Lewis definitions of acids and bases are reviewed in Sec. 7.6. Alcohols are comparable in acidity to water, but phenols are much more acidic. This increased acidity is due to charge delocalization (resonance) in phenoxide ions. Electron-withdrawing groups, such as -F and -N02, increase acidity, through either an inductive or a resonance effect, or both. 

Alkoxides, the conjugate bases of alcohols, are prepared from alcohols by reaction with reactive metals or metal hydrides. They are used as organic bases. Because of the greater acidity of phenols, phenoxides can be obtained from phenols and aqueous base. 

The word alcohol immediately brings to mind ethanol, the intoxicating compound in wine and beer. But ethanol is just one member of a family of organic compounds called alcohols that abound in nature. Naturally occurring alcohols include 2-phenylethanol, the compound responsible for the intoxicating smell of a rose cholesterol, a tasty alcohol with which many of us have developed a love-hate relationship sucrose, a sugar we use to satisfy our sweet tooth and many others. In this chapter, we will discuss the structural and physical properties as well as the main chemical reactions of alcohols and their structural relatives, phenols and thiols. 

Online homework for this chapter can be assigned in OWL, an online homework assessment tool. 

Alcohols have the general formula R—OH and are characterized by the presence of a hydroxyl group, —OH. They are structurally similar to water, but with one of the hydrogens replaced by an alkyl group. Phenols have a hydroxyl group attached directly to an aromatic ring. Thiols and thiophenols are similar to alcohols and phenols, except the oxygen is replaced by sulfur. 

In the lUPAC system, the hydroxyl group in alcohols is indicated by the ending -ol. In common names, the separate word alcohol is placed after the name of the alkyl group. The following examples illustrate the use of lUPAC rules, with common names given in parentheses. 

2-methyl-l-propanol 2-methyl-2-propanol (isobutyl alcohol) (tert-butyl alcohol) 

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ADDITION OF ALCOHOLS, PHENOLS, AND THIOLS TO ALKENE AND ALKYNE BONDS... 

The nucleophilic addition of alcohols [130, 204-207], phenols [130], carboxylates [208], ammonia [130, 209], primary and secondary amines [41, 130, 205, 210, 211] and thiols [211-213] was used very early to convert several acceptor-substituted allenes 155 to products of type 158 and 159 (Scheme 7.25, Nu = OR, OAr, 02CR, NH2, NHR, NRR and SR). While the addition of alcohols, phenols and thiols is generally carried out in the presence of an auxiliary base, the reaction of allenyl ketones to give vinyl ethers of type 159 (Nu = OMe) is successful also by irradiation in pure methanol [214], Using widely varying reaction conditions, the addition of hydrogen halides (Nu= Cl, Br, I) to the allenes 155 leads to reaction products of type 158 [130, 215-220], Therefore, this transformation was also classified as a nucleophilic addition. Finally, the nucleophiles hydride (such as lithium aluminum hydride-aluminum trichloride) [211] and azide [221] could also be added to allenic esters to yield products of type 159. 

As we have seen (pp. 50 et seq.) the reaction between phosphorus oxydichlorofluoride and alcohols, phenols and thiols, affords dialkyl, dicyctoalkyl, diaryl phosphorofluoridates and dialkyl phosphorodithiolates. In a Report1 to the Ministry of Supply on fluorophosphonates a description was given of a new type of nitrogen fluorophosphonate formed by the action of 4 mol. of aniline on 1 mol. of phosphorus oxydichlorofluoride, the fluorine atom being unaffected ... 

Xi Z, Hao W, Wang P et al (2009) Ruthenium(III) chloride catalyzed acylation of alcohols, phenols, and thiols in room temperature ionic liquids. Molecules 14 3528-3537... 

Reactions with Alcohols, Phenols, and Thiols. Chemical transformations effected by trifiic anhydride have been... 

Arylation of a wide range of NH/OH/SH substrates by oxidative cross-coupling with boronic acids in the presence of catalytic cupric acetate and either triethyl-amine or pyridine at room temperature in air. The reaction works for amides, amines, anilines, azides, hydantoins, hydrazines, imides, imines, nitroso, pyrazi-nones, pyridones, purines, pyrimidines, sulfonamides, sulfinates, sulfoximines, ureas, alcohols, phenols, and thiols. It is also the mildest method for NIO-vinylation. The boronic acids can be replaced with siloxanes or starmanes. The mild condition of this reaction is an advantage over Buchwald-Hartwig s Pd-catalyzed cross-coupling. The Chan-Lam C-X bond cross-coupling reaction is complementary to Suzuki-Miyaura s C-C bond cross-coupling reaction. 

With alcohols, phenols and thiols, thioesters are the predominant products (4.104), (4.105). Primary amines react with P4S10 to yield either thiophosphoric (phosphorothioic) diamides or the triamides, depending on the conditions (4.106,4.107) (Chapter 9.10). 

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