Alcohols, acetylation polyhydric

This method is precisely similar to the previous method used for the estimation of the number of hydroxyl groups in a polyhydric alcohol. A known weight of aniline is heated with a mixture of acetic anhydride and pyridine until acetylation is complete the excess of acetic anhydride remaining is... 

As a dibasic acid, malic acid forms the usual salts, esters, amides, and acyl chlorides. Monoesters can be prepared easily by refluxing malic acid, an alcohol, and boron trifluoride as a catalyst (9). With polyhydric alcohols and polycarboxyUc aromatic acids, malic acid yields alkyd polyester resins (10) (see Alcohols, polyhydric Alkyd resins). Complete esterification results from the reaction of the diester of maUc acid with an acid chloride, eg, acetyl or stearoyl chloride (11). 

Chemical methods used for the determination of hydroxyl groups or alcoholic constituents in polymers are based on acetylation [16-18], phthalation [18], and reaction with phenyl isocyanate [18,19] or, when two adjacent hydroxy groups are present in the polymers, by reaction with potassium periodate [9,17]. Alcoholic hydroxyl groups may be found in the following polymers (1) poly(ethylene terephthalate) (PET) [20], (2) poly(methyl acrylate), [21], (3) poly(methyl methacrylate) [21], and (4) polyhydric alcohols in hydrolysates of poly(ester) resins [22]. 

The second method of dissolution is based on solvolysis (Solvolysis method) (6,7,11,12). Under milder conditions (80°C for 30 to 150 min) phenolation was accomplished with an appropriate catalyst, and the chemically modified wood was dissolved in phenol (11). Under similar conditions, woods derivatized by allylation, methylation, ethylation, hydroxylation and acetylation have also been found to dissolve in polyhydric alcohols, such as... 

Mannitol hexanitrate is obtained by nitration of mannitol with mixed nitric and sulfuric acids. Similarly, nitration of sorbitol using mixed acid produces the hexanitrate when the reaction is conducted at 0—3°C and at —10 to —75°C, the main product is sorbitol pentanitrate (117). Xylitol, ribitol, and L-arabinitol are converted to the pentanitrates by fuming nitric acid and acetic anhydride (118). Phosphate esters of sugar alcohols are obtained by the action of phosphorus oxychloride (119) and by alcoholysis of organic phosphates (120). The 1,6-dibenzene sulfonate of D-mannitol is obtained by the action of benzene sulfonyl chloride in pyridine at 0°C (121). To obtain 1,6-dimethanesulfonyl-D-mannitol free from anhydrides and other by-products, after similar sulfonation with methane sulfonyl chloride and pyridine the remaining hydroxyl groups are acetylated with acetic anhydride and the insoluble acetyl derivative is separated, followed by deacetylation with hydrogen chloride in methanol (122). Alkyl sulfate esters of polyhydric alcohols result from the action of sulfur trioxide—trialkyl phosphates as in the reaction of sorbitol at 34—40°C with sulfur trioxide—triethyl phosphate to form sorbitol hexa(ethylsulfate) (123). 

Notable progress in the structural analysis of methylene derivatives of the polyhydric alcohols resulted from the investigations of Hann, Hudson and their co-workers26 80,40-4 into the behavior of these compounds during acetolysis. It was found that a mixture of acetic anhydride, acetic acid and 1-2% sulfuric acid ruptures preferentially any methylene bridge which spans a primary and a secondary position, giving the acetate ester of the primary hydroxyl and the acetoxymethyl ether of the secondary hydroxyl subsequent treatment with sodium methoxide removes each of these substituents. Under similar conditions, the acetolysis of a benzylidene compound results in the replacement of the arylidene residue, wherever it is located in the molecule, by two acetyl groups.16 29 47 48... 

Acetates of fatty [1] and polyhydric [2] alcohols, phenols [3] and chlorophenols [4] have been studied. Fell and Lee [3] described a GC method for the determination of polyhydric phenols in urine, which, having been extracted, were acetylated with acetic anhydride in the presence of 4-dimethylaminopyridine. According to these authors this substance shows much stronger catalytic effects than does the usually used pyridine. The derivatives are formed rapidly and quantitatively even in very dilute solutions. In the absence of the catalyst, bifunctional phenols provide more than one GC peak. Slightly polar OV-210 is recommended for the separation of phenol acetates, but analysis on nonpolar OV-101 leads to tailing, probably as a consequence of insufficient deactivation of the column. 

The second method for liquefaction makes use of solvolysis during the process [8,11]. By using conditions which allow phenolysis of part of the lignin, especially in the presence of an appropriate catalyst, the liquefaction of chemically modified wood into phenols could be accomplished under milder conditions (at 80 C for 30-150 min). Allylated wood, methylated wood, ethylated wood, hydroxyethylated wood, acetylated wood, and others have been found to dissolve in polyhydric alcohols such as 1,6-hexanediol, 1,4-butanediol, 1,2-ethanediol, 1,2,3-propanetriol (glycerin), and bisphenol A using the liquefaction conditions just described. Each of them caused partial alcoholysis of lignin macromolecules [4]. 

The acetylation of monohydric alcohols is, in general, not hindered by the presence of other functional groups in the molecule, but polyhydric alcohols do not react satisfactorily, even in the presence of catalysts.189 It seems that accumulation of OH groups in a molecule reduces the reactivity towards ketene. 

Esterification with acid anhydrides is very widespread, especially for preparative use. Acetyl derivatives are prepared by reacting alcohols with acetic anhydride for identification purposes this method is mainly used with polyhydric alcohols (see p. 311) and with higher-molecular alcohols (sterols, etc.). The alcohol is heated in acetic anhydride, usually in the presence of anhydrous sodium acetate, or also in pyridine, chloroform, or benzene solutions. The isolation is carried out either by diluting the reaction... 

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