Acid anhydrides, purification

Although all four tocopherols have been synthesized as their all-rac forms, the commercially significant form of tocopherol is i7//-n7i a-tocopheryl acetate. The commercial processes ia use are based on the work reported by several groups ia 1938 (15—17). These processes utilize a Friedel-Crafts-type condensation of 2,3,5-trimethylhydroquinone with either phytol (16), a phytyl haUde (7,16,17), or phytadiene (7). The principal synthesis (Fig. 3) ia current commercial use iavolves condensation of 2,3,5-trimethylhydroquiQone (13) with synthetic isophytol (14) ia an iaert solvent, such as benzene or hexane, with an acid catalyst, such as ziac chloride, boron trifluoride, or orthoboric acid/oxaUc acid (7,8,18) to give the all-rac-acetate ester (15b) by reaction with acetic anhydride. Purification of tocopheryl acetate is readily accompHshed by high vacuum molecular distillation and rectification (<1 mm Hg) to achieve the required USP standard. 

Lmine(s)—cont d primary. 916 properties of, 920 purification of. 923-924 pyramidal inversion in, 919-920 reaction with acid anhydrides, 807 reaction with acid chlorides, 803-804... 

Selenium dioxide, by oxidation of selenium by nitric acid, 119 purification, 120 Selenium hexafluoride, 121 Silica gel, platinized, use in preparation of hydrogen bromide, 152 Silicobromoform, 38 analysis of, 41 Silicoethane, hexachlor, 42 Silicoformic anhydride, 42 Silicomolybdic acid, 127 analysis, 128... 

According to ref. 3, nonacarbonyldiiron [Fe2(CO)g] was synthesized by photochemical dimerization of pentacarbonyliron [Fe(CO)s] in a mixture of glacial acetic acid and acetic acid anhydride (10 1) at room temperature employing a Dema irradiation apparatus with a Philips HPK 125 W or TQ 150 W medium pressure mercury lamp. The material should be stored at -25°C in a freezer and handled under an atmosphere of argon. Pentacarbonyliron [Fe(CO)s] was a gift from BASF AG, Germany and was used without further purification. 

Synthesis of phthalocyanine-2,9,16,23-tetracarboxylic acid cobalt(II) complex 48 (R = -COOH M = Co(II)) 0.26 g (2 mmol) water-free cobalt chloride, 1.54 g (8 mmol) 1,2,4-benzenetricarboxylic acid anhydride, 4.8 g (80 mmol) urea and around 20 mg ammonium molybdate are intensively mixed and heated under inert gas in a 100-mL glass vessel at 270 °C for 1 h. The blue-colored reaction mixture was pulverized, stirred in 400 mL 6 M aqueous HCl, filtered, intensively washed with 6 M HCl and then water and acetone. The product was treated in a Soxhlet apparatus with acetone and dried. The phthalocyanine tetracarboxylic acid amide obtained was saponified to the tetracarboxylic acid as follows. 1 g of the tetracarboxylic acid amide was heated in a mixture of 6 g KCl and 15 mL 2 M aqueous KOH at 90 °C until the ammonia evolution became weak. The filtered product was dissolved in a fairly small amount of 2 M NaOH and after filtration from byproducts separated with 2 M HCl and isolated by centrifugation. Purification was achieved by dissolving in 0.05 M NaOH, separation with 2 M HCl and centrifugation until the filtrate is free of chloride ions. Yield from 1 g tetracarboxylic acid amide 0.56 g (38%). IR (KBr) 1698, 1373, 1326, 1150, 1091, 743 cm . 

When water is chemically removed, a basic catalyst, such as triethyl-amine, pyridine, jS-picoline, or isoquinoUne, and acetic anhydride is added. Water produced in the imidization is chemically removed by the reaction with acid anhydride. However, this method, requires a process for purification of a reaction mixture to remove the residue, such as tertiary amines and acetic anhydrides, out of the system. 

Selective iV-acylation of iV-desulphated heparin and of IV-deacetylated glycosaminoglycans can be accomplished with acid anhydrides in formamide at room temperature.Heparin coupled to agarose cyclic imidocarbonate has been used as the affinity matrix in the purification of antithrombins. ... 

The oxidation of higher alkanes leads to a large variety of oxidation products, including organic acids, aldehydes, ketones, and alcohols. In most cases the advantage of the cheap alkane feed is eliminated by the large effort required for the tedious separation and purification of the alkane oxidation product mix. This fact has restricted alkane oxidation processes in the chemical industry to few cases, such as, for example, butane oxidation to maleic acid anhydride. 

Acetic Acid 85 237-273 114-134 - E - - in acetic anhydride purification. Plus 10 percent acetic anhydride. 5 percent water, acetone, acetonitride. amines, etc. Alloy C 0.1 mpy... 

Acid anhydrides and chlorides are reactive as the electrophile for activation of dimethyl sulfoxide. Preparatively useful procedures based on acetic anhydride/ trifluoroacetic anhydride,and oxalyl chloride have come into general use. The pyridine-SOa complex is also useful.Scheme 10.3 gives some representative examples. Entry 4 is an example of the use of a water-soluble carbodiimide as the activating reagent. The modified carbodiimide facilitates product purification by providing for easy removal of the by-product urea formed from the carbodiimide. 

Form Supplied in yellow solid commercially available. Preparative Methods the most convenient procedure involves the reaction of PhsCCl with SUver(I) Tetntfluoroborate in ethanol. The most economical route employs the reaction of Ph3CCl with the anhydrous Tetraftuoroboric Acid-Et20 complex, or PhsCOH with HBF4 in acetic anhydride. Purification recrystallization of commercial samples from a minimal amount of dry MeCN provides material of improved purity, but the recovery is poor. ... 

The crude phthalic anhydride is heated and held at 260 C to allow some byproduct reactions to go to completion. Purification is by continuous distillation in two columns. In the first column, maleic anhydride and benzoic and toluic acids are removed overhead. In the second column, pure phthalic anhydride is removed overhead. High boiling residues are removed from the bottom of the second column. 

The cmde phthaUc anhydride is subjected to a thermal pretreatment or heat soak at atmospheric pressure to complete dehydration of traces of phthahc acid and to convert color bodies to higher boiling compounds that can be removed by distillation. The addition of chemicals during the heat soak promotes condensation reactions and shortens the time required for them. Use of potassium hydroxide and sodium nitrate, carbonate, bicarbonate, sulfate, or borate has been patented (30). Purification is by continuous vacuum distillation, as shown by two columns in Figure 1. The most troublesome impurity is phthahde (l(3)-isobenzofuranone), which is stmcturaHy similar to phthahc anhydride. Reactor and recovery conditions must be carefully chosen to minimize phthahde contamination (31). Phthahde [87-41-2] is also reduced by adding potassium hydroxide during the heat soak (30). 

These precursors are prepared by reaction of fuming nitric acid in excess acetic anhydride at low temperatures with 2-furancarboxaldehyde [98-01-1] (furfural) or its diacetate (16) followed by treatment of an intermediate 2-acetoxy-2,5-dihydrofuran [63848-92-0] with pyridine (17). This process has been improved by the use of concentrated nitric acid (18,19), as well as catalytic amounts of phosphoms pentoxide, trichloride, and oxychloride (20), and sulfuric acid (21). Orthophosphoric acid, -toluenesulfonic acid, arsenic acid, boric acid, and stibonic acid, among others are useful additives for the nitration of furfural with acetyl nitrate. Hydrolysis of 5-nitro-2-furancarboxyaldehyde diacetate [92-55-7] with aqueous mineral acids provides the aldehyde which is suitable for use without additional purification. 

An especially interesting case of oxygen addition to quinonoid systems involves acidic treatment with acetic anhydride, which produces both addition and esterification (eq. 3). This Thiele-Winter acetoxylation has been used extensively for synthesis, stmcture proof, isolation, and purification (54). The kinetics and mechanism of acetoxylation have been described (55). Although the acetyhum ion is an electrophile, extensive studies of electronic effects show a definite relationship to nucleophilic addition chemistry (56). 

Further purification is accomplished, if desired, by the original directions. The acid, as prepared above, always contains traces of nitric acid, but is satisfactory for conversion into the anhydride. If the catalyst is omitted, the yield is less by 10 per cent. 

Purification as their N-acetyl derivatives is satisfactory for primary, and to a limited extent secondary, amines. The base is refluxed with slightly more than one equivalent of acetic anhydride for half to one hour, cooled and poured into ice-cold water. The insoluble derivative is filtered off, dried, and recrystallised from water, ethanol, aqueous ethanol or benzene (CAUTION toxic ). The derivative can be hydrolysed to the parent amine by refluxing with 70% sulfuric acid for a half to one hour. The solution is cooled, poured onto ice, and made alkaline. The amine is steam distilled or extracted as above. Alkaline hydrolysis is very slow. 

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