Chloroacetic acid, 293 Table

With simple alkyl groups attached to the a-carbon of the carboxylic acid (the acids in Table 9.11) the pKa s are all about the same (as measured in aqueous ethanol). However, as seen with the chloroethanoic (chloroacetic) acids (Table 9.11), the effect of electron-withdrawing groups is to increase the acidity (decrease the pKa) of the carboxylic acid. As expected, a correlation can also be effected with the corresponding downfield shifts of the chlorine bearing carbon atom in the respective NMR spectra of the chloroethanoic (chloroacetic) acids. 

The physical properties of cyanoacetic acid [372-09-8] and two of its ester derivatives are Hsted ia Table 11 (82). The parent acid is a strong organic acid with a dissociation constant at 25°C of 3.36 x 10. It is prepared by the reaction of chloroacetic acid with sodium cyanide. It is hygroscopic and highly soluble ia alcohols and diethyl ether but iasoluble ia both aromatic and aUphatic hydrocarbons. It undergoes typical nitrile and acid reactions but the presence of the nitrile and the carboxyUc acid on the same carbon cause the hydrogens on C-2 to be readily replaced. The resulting malonic acid derivative decarboxylates to a substituted acrylonitrile ... 

Economic Aspects. Eigures on U.S. production, imports, and projected demand of chloroacetic acid are Hsted in Table 2 (24). The majority of imported chloroacetic acid is produced in Germany. Western European capacity for chloroacetic acid is in excess of 225,000 metric tons per year. In 1990 the price was 1.25 to 1.36/kg (24,25). 

TABLE 8.7 Thermodynamic Values for the Ionizations of Acetic and Chloroacetic Acids in HjO at 25° C... 

Compound 451 (R1 =aryl) in refluxing chloroacetic acid and in the presence of anhydrous sodium acetate gives 2-substituted aryl-imidazo[2,l- ][l,3,4]thiadiazoles 161 (unreported yields) (Equation 103) (Table 59) <1997JIC125>. Under the same experimental conditions, compound 451 (R1 = 4-Bu1) is transformed to the corresponding derivative 161 in 68% yield (Equation 103) (Table 59) <2000IJH255>. 

Synthetic approaches to representatives of this ring system have been discussed in CHEC-II(1996) <1996CHEC-II(8)496>. Research activity in this area has been considerably extended during the past years. Thus, the basic starting material is a 6,6-disubstituted tetrahydro[l,2,4,5]tetrazin-3-thione 52, which has been converted in three different ways reaction with phenacyl bromides led to 3,3-disubstituted 3,4-dihydro-6-phenyl-2//-thiazolo[3,2-4]-[l,2,4,5]tetrazines 53, reaction of 52 with 1,2-dibromoethane gave 3,4,6,7-tetrahydro-2//-thiazolo[3,2-7][l,2,4,5]tetra-zines 54, whereas transformation of 52 with chloroacetic acid in the presence of sodium acetate yields substituted 3,4-di hydro-1-2//-thiazolo[3,2- 1 [ 1,2,4,5]tctrazin-6(7//)-oncs 55 <2001IJB584> (Scheme 17). Details are shown in Table 2. 

From Table 5.1, we can see that a particular chloroacetic acid-chloroacetate combination would give a pH of 2.00. Rearranging Equation (5.28), we have... 

TABLE 8.6 Thermodynamic values for the ionizations of acetic and chloroacetic acids in H20 at 25°C157... 

The result of this inductive effect is that the electron density on the carboxylate anion is reduced, the negative charge is distributed over more atoms, and the chloroacetate anion is stabilized relative to acetate. Because the chloroacetate anion is more stable than the acetate ion, its conjugate acid, chloroacetic acid, is a stronger acid than the conjugate acid of the acetate ion, acetic acid (Table 3.1). 

Data for aliphatic aldehyde enolisation are very scarce, probably because the enolisation process is often complicated by oxidation and hydration. Nevertheless, the rate constants for base- and acid-catalysed iodination of R R2CHCHO were determined in aqueous chloroacetic acid-chloroacetate ion buffers (Talvik and Hiidmaa, 1968). The results in Table 4 show that alkyl groups R1 and R2 increase the acid-catalysed reactivity in agreement with hyperconjugative and/or inductive effects. This contrasts with aliphatic ketones for which steric interactions are important and even sometimes dominant. Data for base-catalysis are more difficult to interpret since a second a methyl group, from propionaldehyde to isobutyraldehyde, increases the chloroacetate-catalysed rate constant. This might result from a decrease of the a(C—H) bond-promoted hyperconjugative stabilisation of the carbonyl compound... 

A small part of the primary product rearranges to form diphenylacetic acid. The reaction rate is proportional to the product of concentrations of substrate and H30+, and the solvent isotope effect (kH/kD ) is larger than 1 (Table 19) [220, 221]. General catalysis by chloroacetic acid has been observed [220]. The reaction rate is increased by electron-releasing substituents and decreased by electron-withdrawing substituents at the aromatic ring. The data follow Hammett s rule with a p value of —2.38 [221]. There is no doubt that the reaction takes place with ratedetermining proton transfer in the first step (A-SE2 mechanism). The same conclusion may be drawn on the basis of similar evidence for the acid catalyzed hydrolysis of 2-diazoacenaphthenone [222]. 

The term lEP has been used even quite recently for a zero point determined by drift method [18]. The principle of the method is as follows. A series of buffer solutions of equal volume and different pH (in this instance chloroacetic acid-sodium chloroacetate for acidic range and NH3-NH4NO3 for basic range) is prepared. The same amount of powder is added to each solution and the pH of the slurry is measured. The instant change in pH (negative or positive) induced by addition of powder is plotted as the function of initial pH. The pH at which this change equals zero is taken as the zero point. This method is in fact a modified potentiometric titration without correction. Consequently such results are referred to as pH in Table 3.1. Moreover, weak acids often adsorb specifically and this affects the obtained zero point, thus pristine value can be only obtained in case of fortuitous coincidence using this method. 

Table IIL Thb Ionization Constant of Chloroacetic Acid from Ostwald s Dilution Law, =389.5...

Polyamine chain extension, 48-56 by acrylamide 51, 52. 53 by aziridine 48,49 by l-bromo-3-chloropropane, 55 by (2-bromoethyl)phthalimide, 51 by 3-bromopropylphthalimide, 53 by chloroacetonitrilc, 51 by chloroacetyl chloride. 50 by lV-(2-chloroethyl)acetamide, 52 by derivatives of chloroacetic acid. 50 by dichloro(o)-bromoalkyl)boranes. 56 by IV-ethylchloroacetamide, 52 by 3-phthalimidopropyl tosylate, 54 by /V-tosyl-2-bromoethylamine, 49 by 2-(N-tosylamino)ethyl tosylate. 49 by Af-tosylaminoacetyl chloride, 50 Polyamino diols. 59 Polyaza-crown macrocycles. 349-367 alkyl-substituted. 364.365 from bis-sulfonamides, 358-361 from diacid dichlorides, 352-357 from diesters, 352-357 from dihalides, 362-366 from diols, 366 from ditosylates. 362-366 Polyaza-crown macrocycles (miscellaneous), table. 392... 

In Table 4.3 the calculated pH values for the organic acids for which dissociation constants are available in the literature are compiled. It shows that the concentration of H -ions which 1 mole of an organic acid can produce ranges from lo" mole T for chloroacetic acid to mole T for trimethylacetic acid. Carbonic acid may furnish... 

By carboxyalkylation of alkylamines, alkyletheramines or alkylpolyamines, either with chloroacetic acid or acrylic acid (or their derivatives), a multitude of special amphoteric surfactants can be achieved. An overview is given in Table 15.3. 

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