Dichloroacetic acid, 293 Table

The outflow of a sewage pipe continuously adds dissolved dichloroacetic acid methyl ester (dichloromethylacetate, DCMA) to a small river. The mean concentration in the effluent is 400 pg L 1. In the river, DCMA undergoes a base-catalyzed reaction (see Table 13.8). At a water temperature of 15°C, kh is 0.2 h-1 for pH = 7 and 2.0 h 1 for pH = 8. 

Cg and C", are the initial concentrations of ethoxysilane an methanol, respectively. The two different data treatments gave essentially identical values of k. Dividing k by the concentration of the dichloroacetic acid yields the rate constant, k, for the reaction. Table 6 contains the rate data for each of the alcoholysis reactions of the p-substituted phenyldimethylethoxysilanes. 

Metabolism of 1,1-dichloroethane by hepatic microsomes resulted in the production of acetic acid as the major metabolite and 2,2-dichloroethanol, mono-, and dichloroacetic acid as minor metabolites (Table 2-4) (McCall et al. 1983). On the basis of these results, pathways for the metabolism of 1,1-dichloroethane were proposed (Figure 2-3). The initial steps in the metabolism of 1,1-dichloroethane were proposed to involve cytochrome P-450-dependent hydroxylations at either carbon. Hydroxylation at C-1 would result in the production of an unstable alpha-haloalcohol, which can lose HCI to yield acetyl chloride. An alternative, but less favorable reaction, would be a chlorine shift to yield chloroacetyl chloride. These acyl chlorides can react with water to generate free acids or react with cellular constituents. Hydroxylation at C-2 would produce 2,2-dichloroethanol, which would undergo subsequent oxidation to dichloroacetaldehyde and dichloroacetic acid (McCall et al.1983). 

High amylose starch, treated with formamide and dichloroacetic acid and a plasticizer yield homogenous, flowable quasi-solutions without formation of gels when they are heated, with stirring, to temperatures above 80°C. As plasticizers serve ethylene glycol, triethylene glycol, poly(vinyl alcohol), and glycerol (13). The properties of such prepared compositions are shown in Table 7.4. 

Table 1. Enthalpy of dilution of poly(7-benzyl-L-glutamate) (M (C2H2CI2O2) at 298.15 K [1968KAG1]. = 290000 g/mol) in dichloroacetic acid ...

The hydroxyl groups in these products are determined by acetylation with an excess of dichloroacetic anhydride in dichloroacetic acid at 60 C and measurement of the amoimt of acetylation by a chlorine determination either by potentiometric titration with silver ions after combustion or by X-ray fluorescence spectroscopy of a compressed disc of the polymer. The suitability of this method for a number of samples is demonstrated in Table 1.12. The standard deviation of the method for high relative molecular weight polymers is 0.7 mmol kg whereas for the low relative molecular weight materials, it is about 10 mmol kg ... 

An example of the determination of the optical shear coefficients An/Ax (FBF method) for samples and fractions of an aromatic polyether (PE, polymer 6 in Table 3.11) in dichloroacetic acid is shown in Fig. 3.22. Figure 3.22 shows that the values of An/(Ax) for PE [102] (there are similar data for P-IO-MTOC [101, 103]) are essentially dependent on the molecular weight of the polymer. This means that the molecules of these polymers exhibit optical properties characteristic of rigid-chain polymers [10]. The experimental dependence of Art/(At) = [n]/[T]] on M can be used for estimating the equilibrium rigidity of the macromolecules from the optical data [7,108]. The experimental data shown in Fig. 3.22 are compared with the theoretical dependence [Eqs. (6)-(8)] for polymer PE [108]. The optical characteristics of the low-molecular-weight frag-... 

TABLE 3.11. Optical and Electrooptical Properties of Macromolecules with Mesogenic Groups in the Main Chain in Dichloroacetic Acid... 

Table 3.4 Results of catalytic liquid phase hydrodechlorination of dichloroacetic acid (unpublished results Diploma thesis Pratap Patil, Humboldt-University 2005)...

A marked decrease, compared to water, in lyophobic interactions towards the nonpolar residues of the protein. Of the common strongly protic liquids, only hydrofluoric acid, formic acid, and hydrazine are not completely miscible with simple hydrocarbons, while the others, such as ethylenediamine, dichloroacetic and trifluoroacetic acids, are completely miscible with them. Even in the cases of hydrofluoric acid, formic acid, and hydrazine, the solubility of hydrocarbons is much greater than in water. Thus, a satmated solution of benzene in formic acid at 25°C contains 0.088 mole fraction of benzene, compared to 0.00035 mole fraction of benzene in water (see Section IV,B,3 and Table IV). 

PROBLEM 10.6 Using the data given in Table 10.4, determine which is the stronger acid, acetic or dichloroacetic, and by how much. 

The a values obtained in this manner have an uncertainty of 0.08 and are listed in Table 3.9 adopted from [3]. Water has a large value of a = 1.17, but certain phenols and halogen-substituted alkanols and carboxylic acids are considerably more acidic hexafluoro-i-propanol has a = 1.96, dichloroacetic add has a = 2.24, and trifluoro-methanesulfonic acid has AN = 131.7, much higher than the value for water, 54.8, but these are rarely used as solvents for electrolytes and therefore are not dealt with further here. 

Quantitative studies of the hydrodynamic characteristics were conducted in [100-103] for the polymers and copolymers listed in Table 3.10, and only copolymers of 3 are soluble in tetrachloroethane [100], while alkylene aromatic polyethers are soluble in dichloroacetic and trifluoroacetic acids [101-103]. The use of acids with a high viscosity and density as solvents limits the possibilities of the sedimentation method. For this reason, for polydecamethylene-tere-phthaloyl di-p-hydroxybenzoate (P-IO-MTOC, polymer 1) and the totally aromatic polyether (PE) containing aromatic rings in the meta and para positions (polymer 2), the molecular weights of the fractions and samples were either determined with the Svedberg equation using sedimentation-diffusion data... 

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