June 27, 2008
Although NMR offers some strategies for determining the presence of a fluorine atom(s), fragment loss of a CF3 group can be determined from a mass spectrum.
The EI MS for 2,2,2-trifluoro-N,N-dimethylacetamide (Mmi = 141 Da) is shown below. The ion peak at m/z 72 indicates the loss of a CF3 group. Although the ion peak at m/z 69 may not always be present, instead be on the lookout for this fragment loss of 69 Da.