Evidence for Cyclic Bromonium lons L. NMR Studies i. Symmetrical Case Me sbF5 Not observed Me SbF5 So2 Dichloro and diiodo compounds behave much like the dibromide Two distinct types of methyl groups for the fluoro compound indicates that a B-fluoro carbocation is the majo ediate for this compound. The fluorine resonance is also indicative of an oper The bromo compound exhibits only one methyl resonance even when cooled to-1200C Olah G.A. J. Am. Chem. Soc. 1967. 89. 4744 PA-Bromonium 04 10/5/00 6: 46 PMOlah, G. A. J. Am. Chem. Soc. 1967, 89, 4744 Olah, G. A. J. Am. Chem. Soc. 1968, 90, 947 Evidence for Cyclic Bromonium Ions I. NMR Studies i. Symmetrical Case: SbF5 SO2 + + Not observed + SbF5 SO2 + Dichloro and diiodo compounds behave much like the dibromide Two distinct types of methyl groups for the fluoro compound indicates that a β-fluoro carbocation is the major intermediate for this compound. The fluorine resonance is also indicative of an open carbocation. The bromo compound exhibits only one methyl resonance even when cooled to -120° C. . . . Me F Me F Me Me Me Me F Me Me F Me Me Br Me Br Me Me Me Br Me Me Br 09A-Bromonium 04 10/5/00 6:46 PM