Obtaining structural information of perfluoro‐1,3‐dimethyladamantane from collisionally activated decomposition mass spectra

Cyclic, high molecular weight perfluorocarbons (PFC's) are very electronegative, and can be detected by methane negative ion chemical ionization (NICI); however only molecular ions are detected. Electron ionization (EI) of PFC's, on the other hand, yields little or no molecular ion but very intense low mass fragment ions such as CF 3+ (m/z 69), C₃F 5+ (m/z 131) and C₄F 7+ (m/z 181), which are not structurally characteristic. High‐energy collisionally activated decomposition (CAD) of positive, molecular ions of perfluoro‐1,3‐dimethyladamantane yields important structural information by providing more intense high mass fragment ions. Fragments of the following formulae and abundances (in brackets): C₅F 11+ (100), C₁₁F 17+ (73), C₇F 9+ (67), C₈F 11+ (43), C₄F 7+ (26), C₇F 8+. (18), and CF 3+ (14) are detected by this method.