Microscale preparation of isotopically enriched CF235Cl37Cl

Isotopically enriched (CF2ClCl)-Cl-35-Cl-37 (similar to 94% isotopic purity) has been synthesised by a three-step reaction. CHF2CO2H, Cl-35(2) (99% isotopic purity) and Cl-37(2) (95% isotopic purity) have been used as reactants. intermediate products (CF2ClCO2H)-Cl-35 and (CF2ClCO2Ag)-Cl-35 have been obtained. The yield of spectroscopically pure (CF2ClCl)-Cl-35-Cl-37, With respect to CHF2CO2H, is ca. 18%. Isotopic enrichment of (CF2ClCl)-Cl-35-Cl-37 has been checked employing the splitting of chlorine isotopes observed in the gas-phase infrared spectrum for the nu(6) band region. The preparation has been improved to 1 mmol scale, obtaining a sample suitable for infrared measurements. The selective process is a general method to synthesise alternatively the three isotopic species (CF2ClCl)-Cl-35-Cl-37, (CF2Cl2)-Cl-35 and (CF2Cl2)-Cl-37. (C) 1999 Elsevier Science S.A. All rights reserved.