Hydroxyl group, alcohols

AC2O, BF3 Et20, THE, 0°. These conditions give good chemoselectivity for the most nucleophilic hydroxyl group. Alcohols are acetylated in the presence of phenols. 

An alcohol may be acyclic or cyclic. It may contain a double bond, a halogen atom or additional hydroxyl groups. Alcohols are usually classified as primary (1°), secondary (2°) or tertiary (3°). When a hydroxyl group is linked directly to an aromatic ring, the compound is called a phenol (see Section 4.6.10), which differs distinctly from alcohols. 

Protection of hydroxyl groups. Alcohols are converted into SEM ethers in high yield on reaction with 1 and diisopropylethylamine. Deprotection is effected by treatment with h-Bu4NF in THF or HMPT at 45°. 

Let hydroxyl groups (alcohols) from the two polymer chains play the role of the two alcohols in the equation provided for formation of borate esters. Borate ester formation cross-links the two polymer chains as follows ... 

Phosphorylation. Dibenzyl phosphorochloridate is widely used for phosphorylation of alcohols, but is more difficult to prepare than the fluoridate. Phenol is very readily phosphorylated by 1 and CsF in CH3CN, and indeed a phenolic hydroxyl group is selectively attacked even in the presence of a primary hydroxyl group. Primary and anomeric alcohols are preferentially phosphorylated in the presence of a secondary hydroxyl group. Alcohols that are insoluble in acetonitrile can be phosphorylated by 1 and DBU in place of CsF. 

Protection of hydroxyl groups. Alcohols and phenols react with 1 and tri-ethylamine to form tetrahydro-2-furanyl (THF) ethers (85-98% yield). The reaction of acids with 1 results in THF esters. These derivatives are stable to base and nucleophilic reagents they are readily removed by acid-catalyzed hydrolysis or methanolysis. One synthetic application is conversion of the ethers into alkyl bromides by reaction with triphenyphosphine dibromide (1,1247-1248), a reaction that is faster than that with the free alcohols. 

On the shelves of drugstores you can find bottles of ethanol labeled denatured alcohol. Denatured alcohol is ethanol to which small amounts of noxious materials such as aviation gasoline or other organic solvents have been added. Ethanol is denatured in order to make it unfit to drink. Because of their polar hydroxyl groups, alcohols make good solvents for other polar organic substances. For example, methanol, the smallest alcohol, is a common industrial solvent found in some paint strippers, and 2-butanol is found in some stains and varnishes, as shown in Figure 23-5. Perform the CHEMLAB at the end of this chapter to learn about some other properties of small-chain alcohols. 

Protic polar solvents such as alcohols are necessary to solubilize polar functional monomers and their polymers. Due to the robust nature of several catalysts to hydroxyl groups, alcohols can be employed in the metal-catalyzed living or controlled radical polymerization. 

Oxidation of hydroxyl groups. Alcohols are not ordinarily oxidized by... 

On account of their hydroxyl groups alcohols (DIN 53245) differ from aliphatic, aromatic, and chlorinated hydrocarbons by having a higher polarity and a stronger... 

Functional Derivatives of Hydroxyl Groups. Alcohol groups can be esterified. This reaction is used frequently in organic chemistry for the purpose of characterizing sugars or for blocking certain hydroxyl groups. Acetate or benzoate esters often serve in syntheses with carbohydrates. 

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