Other mixed esters

OTHER MIXED ESTERS Tripentaerytfaritol octanitrate (Nitrotripenta) 

Tripentaerythritol octanitrate (Nitrotripenta) melting at 82-83°C was prepared by Wyler [57] by nitrating tripentaerythritol (m.p. 248-250°C), another by-product of the pentaerythritol reaction. 

The formation of tripentaerythritol is favoured by keeping high alkalinity in the pentaerythritol reaction, by using potassium hydroxide or by carrying out the pentaerythritol reaction in the presence of pentaerythritol or dipentaerythritol [58]. 

Nitrotripenta has been prepared by the nitration of tripentaerythritol with 99% nitric acid at 0-10°C. Nitrotripenta is readily soluble in hot benzene and in acetone, soluble in alcohol and chloroform, insoluble in water. Because of its relatively low melting point, nitrotripenta can be melted and poured, and can therefore be used as a coating agent and sensitizer for ammonium nitrate. 

Tetrapentaerythritol decanitrate (Nitrotetrapenta) m.p. 70°C was prepared by Wyler [59] by nitrating tetrapentaerythritol (m.p. 234°C). 

OTHER MIXED ESTERS Tripentaerythritol octanitrate (Nitrotripenta) 

---

Other mixed esters, eg, cellulose acetate valerate [55962-79-3] cellulose propionate valerate [67351-41-17, and cellulose butyrate valerate [53568-56-2] have been prepared by the conventional anhydride sulfuric acid methods (25). Cellulose acetate isobutyrate [67351-38-6] (44) and cellulose propionate isobutyrate [67351-40-0] (45) have been prepared with a 2inc chloride catalyst. Large amounts of catalyst and anhydride are required to provide a soluble product, and special methods of delayed anhydride addition are necessary to produce mixed esters containing the acetate moiety. Mixtures of sulfuric acid and perchloric acid are claimed to be effective catalysts for the preparation of cellulose acetate propionate in dichi oromethane solution at relatively low temperatures (46) however, such acid mixtures are considered too corrosive for large-scale productions. 

Systematic investigations were carried out for the preparation of cellulose acetate of D.S. 2,65 and other mixed esters which included cellulose acetate-propionate, cellulose acetate-butyrate, cellulose acetate-benzoate and cellulose acetate-methacrylate. The experimental conditions were optimised for maximum yield of the ester. Flat osmotic membranes were developed from these esters and characterised for their osmotic and transport properties. The nmmbra-nes were evaluated in a reverse osmosis laboratory test-cell using 5OOO ppm sodium chloride solution at 40 bars pressure. Table 1 presents the typical performance data of these membranes. 

Various other diesters, mixed esters, and polyesters of trimethylpentanediol are useful as monomeric or polymeric plasticizers for coatings and plastic film and sheeting (49). They are compatible with, and useful ia, ceUulosics, vinyls, polystyrenes, and some other plastics. 

Uses. Phthabc anhydride is used mainly in plasticizers, unsaturated polyesters, and alkyd resins (qv). PhthaUc plasticizers consume 54% of the phthahc anhydride in the United States (33). The plasticizers (qv) are used mainly with poly(vinyl chloride) to produce flexible sheet such as wallpaper and upholstery fabric from normally rigid polymers. The plasticizers are of two types diesters of the same monohydric alcohol such as dibutyl phthalate, or mixed esters of two monohydric alcohols. The largest-volume plasticizer is di(2-ethylhexyl) phthalate [117-81-7] which is known commercially as dioctyl phthalate (DOP) and is the base to which other plasticizers are compared. The important phthahc acid esters and thek physical properties are Hsted in Table 12. The demand for phthahc acid in plasticizers is naturally tied to the growth of the flexible poly(vinyl chloride) market which is large and has been growing steadily. 

We have also investigated other oxalate esters as a potential means to improve the efficiency. The most commonly used oxalates are the 2,4,6-trichlorophenyl (TCPO) and 2,4-dinitrophenyl (DNPO) oxalates. Both have severe drawbacks namely, their low solubility in aqueous and mixed aqueous solvents and quenching of the acceptor fluorescence. To achieve better solubility and avoid the quenching features of the esters and their phenolic products, we turned to difluorophenyl oxalate (DFPO) derivatives 5 and 6 (Figure 14). Both the 2,4- and the 2,6-difluoro esters were readily synthesized and were shown to be active precursors to DPA chemiluminescence. In fact, the overall efficiency of the 2,6-difluorophenyl oxalate 5 is higher than for TCPO in the chemical excitation of DPA under the conditions outlined earlier. Several other symmetrical and unsymmet-rical esters were also synthesized, but all were less efficient than either TCPO or 2,6-DFPO (Figure 14). 

In Formula 33 is pictured a completely mixed ester of a thiophosphate in which all groups are different. The thiophosphoryl chloride method was used for preparing such compounds. It was of interest to see whether or not other compounds could be prepared by the condensation of a dialkyl chlorothiophosphate with a phenol to give products such as shown in Formulas 34 to 36. 

The methyl esters of stearoylalanine [1] and stearoylserine [2] were considered as quasi-racemate candidates because of their slight structural differences. No quasi-racemate behavior was observed, however, in their force-area isotherms although clear diastereomeric discrimination was seen for this combination (Verbiar, 1983). We have seen no indication of quasi-racemate behavior for any other mixed chiral monolayers. 

Serine.—Its ester is contained in the fractions which distil between ioo° and 130° at O 5 mm. The mixed esters contained in this fraction are treated with a small quantity of water and then with five to six volumes of petroleum ether, which precipitates serine ester as an oil the oil is then shaken up with petroleum ether to remove admixtures as far as possible and is hydrolysed with baryta water. On removal of the baryta it crystallises when the solution is concentrated, and it is purified by treatment with alcohol, which dissolves other substances which are also present, and recrystallisation from water. Its )8-naph-thalene sulpho-derivative. 

The fifth sapphyrin-phosphate structure to be solved is of the mixed chlo-ride/monobasic cyclic AMP salt of diprotonated sapphyrin 4 (Figure 9). While the general features of binding are similar to the other phosphate ester structures... 

The addition of alcohols to ketene acetals allows the synthesis of mixed ortho esters [96, 120a-c, 121a, b, 124, 125a, b]. a-Haloaldehydes may be converted to ortho esters by the following process (a) acetal formation, (b) de-hydrohalogenation, and (c) reaction with alcohols via addition reaction (33). In general, the method above, using ketene acetals, is not practical since ketene acetals are not readily available and are difficult to prepare. However, the method is useful because it allows the synthesis of mixed ortho esters and other ortho esters more difficult to synthesize [122-127]. Recently a simple one-step synthesis of ketene acetals and ortho esters has been reported (see p. 56). 

Clement and Riviere [59] also reported that cellulose acetate or a mixed ester — a nitrate-acetate — can be obtained by reacting cellulose nitrate with acetic anhydride, acetic acid, and sulphuric acid. According to more recent contributions, e.g. Wolfrom, Bower and Maker [60], the reaction should be performed as follows Cellulose nitrate is dissolved in the cold in a little sulphuric add and acetic anhydride, the surplus of acetic anhydride is then hydrolysed also in the cold, and cellulose acetate is extracted with a suitable solvent, such as chloroform. Other methods of acetylating nitrocellulose consist in reduction, for instance with zinc and hydrogen chloride, which entails denitration of the ester, followed by acetylation with acetic anhydride. All these reactions are carried out in the same vessel. Further, it is possible to synthesize mixed esters, cellulose nitrate-acetates, by subjecting cellulose to the action of a mixture that includes nitric acid, acetic add and acetic anhydride in the presence of sulphuric acid (Kruger [61]). The use of a large amount of nitric acid favours the formation of nitrocellulose only. Mixed esters are formed... 

The distilled alcohol product mixture was also esterified by refluxing with glacial acetic acid in the presence of a catalytic amount of sulfuric acid. The product was extracted with water followed by extraction with saturated sodium bicarbonate solution. It was further washed with water and dried over anhydrous sodium sulfate. The crude ester was distilled, and the distillate was stored for further use. The percent yield of esters was 86%. The mixed ester was determined by GC to be composed of (1.3%) methyl acetate, (1.3%) ethyl acetate, (11.5%) n-propyl acetate, (81.7%) isobutyl acetate, (1.2%) 2-methy 1-1-butyl acetate, and (1.9%) other components. The composition corresponded closely to that of the parent alcohol mixture. The fuel characteristics of the alcohol mixture and the ester mixture prepared from it were reported earlier (24). 

Other 2-ethylhexanol based plasticizers were introduced, including some which imparted outstanding low temperature flexibility—dioctyl adipate (DOA), dioctyl azelate (DOZ), dioctyl sebacate (DOS), and trioctyl phosphate (TOF). In addition, TOF showed high resistance to microorganisms which was important in military applications. Furthermore, TOF improved flame resistance. However, the mixed ester—octyl diphenyl phosphate—also introduced in the forties—was far superior and showed a better balance of low temperature performance and flame resistance than either TOF or the well-established plasticizer—tricresyl phosphate (TCP). Each of these found a market as a specialty plasticizer because of these specific performance attributes. None, however, was a serious threat to DOP on an overall price-performance basis. Rather, they were used to supplement the properties of DOP where its performance was inadequate. 

---