The decomposition of chloroacetate ion

Trichloroacetic acid decomposes in certain solvents in the neighborhood of 100° to give chloroform and carbon dioxide. A much higher temperature is required for decomposition in the gas phase and then a different set of products is obtained. The reaction is interesting because it illustrates15 how in at least one case the solvent effect and a whole mass of complex data can be nicely interpreted. 

Experimental measurements were carried out in several different solvents by two or three different methods. In some cases a shaking device was used and the rate of the reaction was followed by the evolution of carbon dioxide. In other cases the course of the reaction was followed by titrations using solutions which were sealed off in glass tubes immersed in thermostats and opened up under standardized sodium hydroxide or acid, as the case demanded. Many different tubes of the same solution were sealed off at once and each tube was used for a point on the time-concentration curve. The rate constant was determined from the slope of the line obtained by plotting the logarithm of the concentration against the time. 

Trichloroacetic acid decomposes in water, alcohol and aniline and other basic solvents but it does not decompose in non-basic solvents such as benzene, carbon tetrachloride, sulfuric and acetic acid. Furthermore, the ethyl ester of trichloroacetic acid dissolves in alcohol but it does not decompose. It is known that this ester does not ionize in alcohol. Trichloroacetic acid, the sodium salt, the barium salt, and the anilinium salt all decompose in water at the same rate and all give beautiful first order constants throughout the whole course of the reaction. It is known that all these salts 

At 70° the specific decomposition rates for the barium salt and the anilinium salt are both 1.754 X10 5, practically the same as for the sodium salt. 

In alcohol, the sodium salt gives a first order constant throughout the whole range, and the results are reproducible as before. The barium salt, however, decomposes more slowly and a first order constant is not obtainable. The anilinium salt dissolved in alcohol, gives an apparent first order constant toward the end of the reaction. An increase in ionic strength through the addition of electrolytes gives an increase in the decomposition rate. 

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