Functionality, hydroxyl

The benzyl group has been widely used for the protection of hydroxyl functions in carbohydrate and nucleotide chemistry (C.M. McCloskey, 1957 C.B. Reese, 1965 B.E. Griffin, 1966). A common benzylation procedure involves heating with neat benzyl chloride and strong bases. A milder procedure is the reaction in DMF solution at room temperatiue with the aid of silver oxide (E. Reinefeld, 1971). Benzyl ethers are not affected by hydroxides and are stable towards oxidants (e.g. periodate, lead tetraacetate), LiAIH, amd weak acids. They are, however, readily cleaved in neutral solution at room temperature by palladium-catalyzed bydrogenolysis (S. Tejima, 1963) or by sodium in liquid ammonia or alcohols (E.J. Rcist, 1964). 

Notice that the carboxyl group that stays behind during the decarboxylation of mal onic acid has a hydroxyl function that is not directly involved m the process Compounds that have substituents other than hydroxyl groups at this position undergo an analogous decarboxylation... 

The alcohol groups of carbohydrates undergo chemical reactions typical of hydroxyl functions They are converted to esters by reaction with acyl chlorides and carboxylic acid anhydrides... 

For monosubstituted alkylphenols, the position of the alkyl radical relative to the hydroxyl function is designated either with a numerical locant or ortho, meta, or para. The alkyl side chain typically retains a trivial name. Thus 4-(l,l,3,3-tetramethylbutyl)phenol, 4-/ f2 octylphenol, and para-tert-octy Tph.eno (PTOP) all refer to stmcture (1). 

The chemical properties and reactions of the aminophenols and their derivatives are to be found in detail in many standard chemical texts (25). The acidity of the hydroxyl function is depressed by the presence of an amino group on the benzene ring this phenomenon is most pronounced with 4-aminophenol. 

Substitution of various groups by amino or hydroxyl functions is industrially unimportant for the production of 2- and 4-aminophenol, but this type of reaction is used for the synthesis of 2- and 4-aminophenol derivatives. However, 3-aminophenol caimot be obtained easily by reduction. It is made by the reaction of 3-aminobenzenesulfonic acid [121 -47-1] with sodium hydroxide under fusion conditions (5—6 h 240—245°C). The product is purified by vacuum distillation (25). 

Polymers. The molecular weights of polymers used in high energy electron radiation-curable coating systems are ca 1,000—25,000 and the polymers usually contain acryUc, methacrylic, or fumaric vinyl unsaturation along or attached to the polymer backbone (4,48). Aromatic or aUphatic diisocyanates react with glycols or alcohol-terrninated polyether or polyester to form either isocyanate or hydroxyl functional polyurethane intermediates. The isocyanate functional polyurethane intermediates react with hydroxyl functional polyurethane and with acryUc or methacrylic acids to form reactive p olyurethanes. 

The stmcturaUy similar starch amylose polymer is linked through the a anomeric configuration. The three hydroxyl functions pet anhydroglucose unit ate noteworthy these hydroxyls ate the active sites for ether formation. 

In the chlorination of 2,4-dichlorophenol it has been found that traces of amine (23), onium salts (24), or triphenylphosphine oxide (25) are excellent catalysts to further chlorination by chlorine ia the ortho position with respect to the hydroxyl function. During chlorination (80°C, without solvent) these catalysts cause traces of 2,4,5-trichlorophenol ( 500 1000 ppm) to be transformed iato tetrachlorophenol. Thus these techniques leave no 2,4,5-trichlorophenol ia the final product, yielding a 2,4,6-trichlorophenol of outstanding quaUty. The possibiUty of chlorination usiag SO2CI2 ia the presence of Lewis catalysts has been discussed (26), but no mention is made of 2,4,5-trichlorophenol formation or content. 

Ghlorophenol Analysis. The chlorophenols can be analy2ed by acidimetric titration of the hydroxyl function (50). This overall method yields only an approximate evaluation for mixtures. To analy2e chlorophenol mixtures, gas chromatography has been the reference method used, as it made it possible to separate and quantify the various chlorophenols (51), but this technique can be a source of errors the gem-chlotinated cyclohexadienones that may be present along with the chlorophenols are broken back down iato lighter chlorophenols under the analysis conditions usually employed. 

Acryflc coating powders have achieved some success in Japan utilizing resins having gflcydyl methylacrylate functionality cured with C q—0 2 dicarboxyflc acids (49). Hybrid polyester—acryflc coating powders have also been reported in which an acid functional polyester resin coreacts with a glycidyl-containing acryflc polymer (50). Hydroxyl functional acryflc resins cured with blocked isocyanates have also been available for many years in the United States and achieved some commercial success as appliance finishes. 

The same chemical mechanisms and driving forces presented for phenol-formaldehyde resins apply to resorcinol resins. Resorcinol reacts readily with formaldehyde to produce resins (Fig. 2) which harden at ambient temperatures if formaldehyde is added. The initial condensation reaction, in which A-stage liquid resins are formed, leads to the formation of linear condensates only when the resorcinol/formaldehyde molar ratio is approximately 1 1 [119]. This reflects the reactivity of the two main reactive sites (positions 4 and 6) of resorcinol [120]. However, reaction with the remaining reactive but sterically hindered site (2-positiori) between the hydroxyl functions also occurs [119]. In relation to the weights of resorcinol-formaldehyde condensates which are isolated and on a molar basis, the proportion of 4- plus 6-linkages relative to 2-linkages is 10.5 1. However, it must be noted that the first-mentioned pair represents two condensa-... 

Replacement of a primary or secondary hydroxyl function with deuterium is usually carried out by first converting the alcohol into a mesylate or tosylate ester, which can then be displaced by treatment with lithium aluminum deuteride. The... 

Isotope labeling by derivative formation with deuterated reagents is useful for the preparation of analogs such as dg-acetonides, da-acetates, da-methyl ethers, dg-methyl esters, etc. The required reagents are either commercially available or can be easily prepared. (The preparation of da-methyl iodide is described in section IX-F. Various procedures are reported in the literature for the preparation of dg-acetone, da-diazometh-ane57.i63.i73 and da-acetyl chloride. ) These reactions can be carried out under the usual conditions and they need no further discussion. A convenient procedure has been reported for the da-methylation of sterically hindered or hydrogen bonded phenolic hydroxyl functions by using da-methyl iodide and sodium hydroxide in dimethyl sulfoxide solution. This procedure should be equally applicable to the preparation of estradiol da-methyl ether derivatives. 

The search for suitable protecting groups of carbonyl and hydroxyl functions has been of continuous importance in steroid chemistry. As a result of these efforts a good selection of protecting groups is now available for use in organic synthesis. 

The reactivity of various steroid alcohols decreases in the order primary > secondary (equatorial) > secondary (axial) > tertiary. The only systematic investigation relating to the selective protection of steroidal hydroxyl functions has been carried out with the cathylate (ethyl carbonate) group. Since only equatorial hydroxyl groups form cathylates this ester has been used as a diagnostic tool to elucidate the configuration of secondary alcohols. 

In the case of polyunsaturated steroids the double bond nearest the hydroxyl function is epoxidized first. 

The configuration was assigned after oxidation of (43) and (44) to the corresponding 3,20-diketones. The diketone obtained from (44) showed an intramolecular bonded hydroxyl absorption at 3450 cm h Inspection of molecular models indicates that only a 12 -hydroxyl function can form an internal hydrogen bond to the 20-carbonyl group. 

A useful process for phenol protection and analysis is exemplified by tlie reaction of estrone with perfluorotoluene [72] (equation 8) The hydroxyl function replaces the 4 fluorme in high yield, and the hydroxyl may be deprotected in 87% yield on treatment with hydroxide... 

When pentafluoromtrobenzene reacts with ortho- or para-ammophenol m dimethylformarmde solution contaimng sodium hydroxide, the 4-fluonne is replaced. Either the amino or the hydroxyl function of the armnophenol can act as the nucleophile dependmg on the reaction conditions [67] (equation 35)... 

A surpnsing feature of the reactions of hexafluoroacetone, trifluoropyruvates, and their acyl imines is the C-hydroxyalkylation or C-amidoalkylaOon of activated aromatic hydrocarbons or heterocycles even in the presence of unprotected ammo or hydroxyl functions directly attached to the aromatic core Normally, aromatic amines first react reversibly to give N-alkylated products that rearrange thermally to yield C-alkylated products. With aromatic heterocycles, the reaction usually takes place at the site of the maximum n electron density [55] (equaUon 5). 

Hydroformylation of nitrile rubber is another chemical modification that can incorporate a reactive aldehyde group into the diene part and further open up new synthetic routes to the formation of novel nitrile elastomers with a saturated backbone containing carboxyl or hydroxyl functionalities. 

The oxidizing capability of Ce(IV) has also been used for block copolymer synthesis starting from hydroxyl functional azo compounds, but not proceeding via the formation of MAIs vide infra). 

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