Chloroacetate anion

Chloroacetate anion is stabilized by electron withdrawing effect of chlonne... 

Stabilization of the chloroacetate anion by the chlorine atom makes the chloroacetate ion less prone to cause an ordering of the solvent because it requires less stabilization through solvation. 

Data for chloroacetate ion in water (Smith, 1943). The reference reaction is the intermolecular esterification of the chloroacetate anion by itself c Galli el al., 1977. pA. -values not measured... 

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). 

It is also possible to convert carbonyl groups into oxirane rings with cenain carbenoid synthons. The classical Darzens reaction, which involves addition of anions of a-chloroacetic esters, has been replaced by the addition of sulfonium ylides (R. Sowada, 1971 C.R. Johnson, 1979). 

Next, display electrostatic potential maps for acetUi chloroacetate, trichloroacetate, 2-chlorohutyrate a 4-chlorobutyrate anions. Compare potentials at the positi between the two oxygens. Classify the anions as havi large, intermediate or small charge in this region. 

Because the dissociation of a carboxylic acid is an equilibrium process, any factor that stabilizes the carboxylate anion relative to undissociated carboxylic acid will drive the equilibrium toward increased dissociation and result in increased acidity. An electron-withdrawing chlorine atom, for instance, makes chloroacetic acid (Ka = 1.4 x 10-3) approximately 80 times as strong as acetic acid introduction of two chlorines makes dichloroacetic acid 3000 times as strong as acetic acid, and introduction of three chlorines makes trichloroacetic acid more than 12,000 times as strong. 

In comparison with other anionics, little has been published concerning methods of analysis of ether carboxylates. Gerhardt et al. [238] investigated the analytical determination of ether carboxylic acids in reaction mixtures obtained by reaction of nonylphenol ethoxylates with sodium chloroacetate as well as by cyanoethylation by different methods. Several methods, used for other surfactants as well [239], can be used for ether carboxylates. 

Carboxylate anions derived from somewhat stronger acids, such as p-nilrobcnzoic acid and chloroacetic acid, seem to be particularly useful in this Mitsunobu inversion reaction.53 Inversion can also be carried out on sulfonate esters using cesium carboxy-lates and DMAP as a catalyst in toluene.54 The effect of the DMAP seems to involve complexation and solubilization of the cesium salts. 

The second reason is that Satchell [78] has shown that in the protonation of m-xylene by catalysts composed of stannic chloride and acetic acid or the three chloroacetic acids as co-catalysts, the rate of reaction is inversely related to the aqueous acidity of these acids. Satchell rightly points out that, since the polymerisations are complicated reactions the rates of which are also affected by the terminating efficiency of the anion derived from the co-catalyst, no valid conclusions can be drawn from such studies about catalytic efficiency in any fundamental sense. He interprets the order of effectiveness of the cocatalysts in terms of the stability of the complexes which they form with the metal halide. 

The formation of cyclopropanes from 7C-deficient alkenes via an initial Michael-type reaction followed by nucleophilic ring closure of the intermediate anion (Scheme 6.26, see also Section 7.3), is catalysed by the addition of quaternary ammonium phase-transfer catalysts [46,47] which affect the stereochemistry of the ring closure (see Chapter 12). For example, equal amounts of (4) and (5) (X1, X2 = CN) are produced in the presence of benzyltriethylammonium chloride, whereas compound (4) predominates in the absence of the catalyst. In contrast, a,p-unsatu-rated ketones or esters and a-chloroacetic esters [e.g. 48] produce the cyclopropanes (6) (Scheme 6.27) stereoselectively under phase-transfer catalysed conditions and in the absence of the catalyst. Phenyl vinyl sulphone reacts with a-chloroacetonitriles to give the non-cyclized Michael adducts (80%) to the almost complete exclusion of the cyclopropanes. 

Again, this produces a favourable tertiary carbocation. Loss of a proton gives the required alkene. Note that potentially three different carbons could lose a proton. The reaction shown generates the most stable product this has the maximum number of alkyl substituents and also benefits from extended conjugation. We then get another aldol-type reaction. The enolate anion is produced from the ethyl chloroacetate, and simple addition yields an anion that is subsequently protonated. 

Ion exchangers can also be made from cellulose, especially for scientific applications. They are prepared from alkali cellulose by reaction, for example, with chloroacetic acid (for preparation of sodium carboxymethylcellulose, see Example 5-6). By conversion with 2-chloroethyldiethylamine one obtains so-called DEAE-cellulose, an anion exchanger carrying 2-diethylaminoethyl groups, -C2H4N(C2H5)2. 

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