Fractionation of the Carbon Isotopes in Decarboxylation Reactions. IV. The Relative Rates of Decomposition of 1-C12 and 1-C13 Trichloracetate Ions

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Abstract
A precise determination of the relative rates of decomposition of 1‐C12 and 1‐C13 trichloracetate ions has been made. The 1‐C12 ion has been found to decompose 1.0338±0.0007 times as fast as the 1‐C13 ion into chloroform and bicarbonate at 70.4°C. Trichloracetate ion has been found to undergo a decomposition reaction which gives chloride ion but no CO2, OH−, nor H+. The ratio of the rate constants for the production of Cl− and bicarbonate is 0.078. The errors in the determination of the effect of isotopic substitution on the rates of chemical reactions are discussed. In the study of the isotopes of carbon, experiments using mass spectrometric analyses of C13 at the natural abundance level are capable of a precision of one order of magnitude better than ones in which the specific activity of C14 is determined by counting.