A procedure is described which allows the preparation of carboxylic acids in which the carbon isotopic composition of the carboxyl carbon atom is known to within better than 0.002% 13C (95% confidence limits). In this procedure, a Grignard reagent is first reacted with CO2 of known isotopic composition. After hydrolysis of the salt of the carboxylic acid, the unreacted CO2 is recovered and the isotopic composition determined. The isotopic composition of the carboxyl carbon is then calculated by difference. A differential error analysis in which all relevant uncertainties are considered is presented. Approximate kinetic isotope effect values for carboxylation of a Grignard reagent at -78°C can be determined from the observed isotopic fractionations, with five observations yielding 12k/13k = 1.059(σ = 0.009).
|Original language||English (US)|
|Number of pages||4|
|Journal||The International Journal Of Applied Radiation And Isotopes|
|State||Published - Jan 1 1978|
All Science Journal Classification (ASJC) codes
- Nuclear Energy and Engineering
- Radiology Nuclear Medicine and imaging