The title compound (1) is prepared in satisfactory yield by reacting CH2N2 with trifluoroacetic anhydride in Et(2)O; the d-analog was obtained by exchange with D2O. H-1, C-13, N-15, O-17, and F-19 NMR spectra of 1 were studied, as well as its IR spectrum. A single isomer is present corresponding to the more stable Z configuration. The structural assignment was made on the basis of quantum mechanical calculations, which revealed that the Z form is some 13.4 kJ mol(-1) more stable than the E form and the activation energy for the E --> Z transition is 64.2 kJ mol(-1). Mass spectra under different experimental conditions were recorded and breakdown pathways of the parent ion of 1 charted.
