DIALKYL PHTHALATE

GaUic acid is heated with about half its weight of water in a copper autoclave until the pressure reaches 1.2 MPa (12 atm) and the temperature is 175°C. Steam and carbon dioxide are released but sufficient water is retained to maintain the pyrogaHol as a Hquid. The cooled solution is decolorized with animal charcoal and is then evaporated until the volatile pyrogaHol distills into iron receivers. The sohdified material is purified by repeated distillation, sublimation, or vacuum distillation at 200°C in the presence of diaLkyl phthalates (8). 

Developments in the USA have led to the availability of terephthalate plasticisers, for example dioctyl terephthalate (DOTP). Whilst these materials are very similar to the corresponding o-phthalate esters they are generally less volatile and are best compared with d-phthalates with one or more carbon atom in the alkyl chain. As with the linear dialkyl phthalates the terephthalates show good fogging resistance. This is a phenomenon in which new cars on storage fields awaiting delivery develop misting on the windows due, apparently, to the volatility of additives in PVC compounds used with the car. 

The chemical industry uses esters for a variety of purposes. Ethyl acetate, for instance, is a commonly used solvent, and dialkyl phthalates are used as plasticizers to keep polymers from becoming brittle. You may be aware that there is current concern about possible toxicity of phthalates at high concentrations, although a recent assessment by the U.S. Food and Drug Administration found the risk to be minimal for most people, with the possible exception of male infants. 

Phthalate esters are widespread contaminants and the dialkyl phthalates are hydrolyzed before degradation of the resulting phthalate (Eaton and Ribbons 1982), which is discussed in Chapter 8, Part 3. For dimethyl phthalate, dimethyl terephthalate, and dimethyl isophthalate only partial hydrolysis may take place (Li et al. 2005). Cocaine is hydrolyzed to benzoate and ecgonine methyl ester by a strain of Pseudomonas maltophilia (Britt et al. 1992). 

Figure 4.22 Analysis of dialkyl phthalates using 3-pm 100 A PS/DVB columns. After Meehan and Saunders [758]. Reproduced by permission of International Scientific Communications...

A mixture with a solution of the peroxide in a dialkyl phthalate plasticiser decomposes exothermically but moderately, (probably catalysed by trace heavy metals in the carbon). 

Recoveries between 103% (dialkyl phthalates) and 71% (n-alkancs, dieldrin, eldrin) were reported when the technique was applied to 25 litre samples. 

Bendova, M., Rehak, K.. Matous, J., and Novak, J.P. Liquid + liquid equilibrium in the ternary systems water + ethanol + dialkyl phthalate (dimethyl, diethyl, and dibutyl phthalate) at 298.15 K, /. Chem. Eng. Data, 46(6) 1605-1609, 2001. Benes M. andDohnal, V. Limiting activity coefficients ofsome aromatic and aliphatic nitrocompounds in water, / Chem. Eng. Data, 44(5) 1097-1102, 1999. 

Engelhard , G., Wallnofer, P.R., and Hutzinger, 0. The microbial metabolism of di-/rbutyl phthalate and related dialkyl phthalates. Bull Environ. Contam. Toxicol, 13(3) 342-347, 1975. 

The major bulk processed thermoplastic using calendering is PVC sheets and films including blends and copolymers. A sample recipe to produce PVC sheet might include a plasticizer such as a dialkyl phthalate, pigment, filler, lubricant, and stabilizer. 

Figure 8.1. Relation of solubility parameters (solpars or Hildebrand 8 values) and carbon numbers in various homologous series of solvents. (4) Normal alkanes, (B) normal chloroalkanes, (C) methyl esters, (D) alkyl formates and acetates, (E) methyl ketones, (F) alkyl nitriles, ) normal alkanols, (H) alkyl benzenes, and (I) dialkyl phthalates.

Since cellulose nitrate is intractable, in 1870 John W. Hyatt added camphor as a plasticizer to flexibilize this plastic. Some 60 years later, Waldo Semon used tricresyl phosphate as a plasticizer for PVC. Dialkyl phthalates, such as dioctyl phthalate (DOP) and other alkyl phthalates which replaced the more toxic tricresyl phosphate, are now used as plasticizers primarily for PVC at an annual rate of 1 million tons. 

Dibutyltartrate is a solv plasticizer for NC, DuPont (Ref 2) obtd a patent for the use of Dibutyltartrate as a constituent of pro-plnts which produce no flash from the gun barrel. An example of such a compn is NC, DNT ester of an org acid, such as dialkyl phthalate, dibutyltartrate or ethyl palmitate Refs 1) Beil 3, 518, (178), [332] 1021 ... 

The swelling method has been used successfully in a classic study by Doty and Zable (7) to evaluate the interaction of various plasticizers with poly(vinyl chloride). Figure 8 shows the n values of a series of dialkyl phthalates as a function of their molecular weight. It can be seen that dibutyl, dihexyl, and dioctyl phthalate have low n values-i.e., high solvent power for poly (vinyl chloride), (PVC), whereas the higher and lower esters have high n values, and therefore low solvent power. 

Figure 8. Dependence of the interaction parameter n on the molecular weight of a homologous series of dialkyl phthalates in P VC (7)...

Table VI gives intrinsic viscosities of PVC in a series of dialkyl phthalates (34). These results lead to the same conclusions as the n value determinations of Doty and Zable illustrated in Figure 8.

Figure 8 shows the effect of increasing molecular weight for a series of normal dialkyl phthalates at 75 p.h.r. An increase in the alkyl chain length increases the transition and critical temperatures. The examples concern a series of normal alkyl esters apart from the ditridecyl phthalate (DTDP) which is added to show the effect of high molecular weight. 

Figure 8. Effect of increasing molecular weight for a series of normal dialkyl phthalates...

Starting with ketones and hydrogen peroxide in the presence of a catalytic amount of acid, mixtures of up to eight components have been identified, i.e.. (1, X = OH. R3 = H), (1, X = OOH, R3 = H), (2, X = Y = OH). (2, X = Y = OOH), (2, Y = OH, Y = OOH), (3). (4), and (5). The ketone structure and reaction conditions, i.e., acid strength, reactant molar ratios, temperature, and time, determine which compounds form and predominate. Mixtures of several peroxide structures usually are present. Individual peroxides have been isolated from several ketones under different conditions (Table 5). The pure peroxides should be handled with extreme caution since most, especially those derived from the low moleculai weight ketones, ate shock- and friction-sensitive and can explode violently. Methyl ethyl ketone peroxide (MEKP) mixtures are produced commercially only as solutions containing <40 wt% MEKPs in solvents, commonly dialkyl phthalates. 

Cerbulis J, Byler DM. 1986. Isolation and detection of dialkyl phthalates from pork. J Agric Food Chem 34 198-200. 

Niino T, IshibashiT, Itho T, et al. 2001. Monoester formation by hydrolysis of dialkyl phthalate migrating from polyvinyl chloride products in human saliva. J Health Sci 47(3) 318-322. 

Smith JH, Isenberg JS, Pugh G, et al. 2000. Comparative in vivo hepatic effects of di-isononylphthalate (DINP) and related C7-Cn dialkyl phthalates on gap junctional intercellular communication (GJIC), peroxisomal beta-oxidation (PBOX), andDNA synthesis in rat and mouse liver. Toxicol Sci. 54 312-321. 

Thomas GH. 1973. Quantitative determination and confirmation of identity of trace amounts of dialkyl phthalates in environmental samples. Environ Health Perspect 3 23-28. 

Yoshikawa K, T anaka A, Yamaha T, et al. 1983. Mutagenicity study of nine monoalkyl phthalates and a dialkyl phthalate using Salmonella typhimurium and Escherichia coli. Food Chcm Toxicol 21 221-223. 

Poly(vinyl chloride) (PVC) is used for rigid structures like window frames and gutters with only small amounts of additives such as pigments. If PVC is used for flexible things like plastic bags, about 20-30% of dialkyl phthalates such as the compound below are incorporated during polymerization. Why is this ... 

Waste constituents may be immobilized in a soil system mainly by sorption and/or partitioning. Adsorption on soil particles is competitive, pH-dependent and, usually, inversely proportional to the solubility of the compound in water. Dry soils are better adsorbents than wet ones. HSs are able to form complexes with metal ions and hydrous oxides and also interact with minerals and a variety of organic compounds, including alkanes, fatty acids, dialkyl phthalates, pesticides and herbicides, and may therefore increase the concentration of these constituents in soil and natural waters. 

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