engleski

Isotopic scrambling in Di-C-13-labeled 2-butyl cation: Evidence for a protonated cyclopropane intermediate

The C-13 NMR spectrum of 2-butyl-1, 2-C-13(2) cation (1) is unchanged on heating the sample to -78 degreesC, indicating no isomerization to another isotopomer. In contrast, the spectrum of 2-butyl-2, 3-C-13(2) cation (2) shows rapid formation of all of the other isotopomers except 1. These results are consistent with a protonated cyclopropane intermediate in the rearrangement process. In this mechanism, either C-1 and C-2 or C-3 and C-4 interchange. Only the bond between C-2 and C-3 breaks

Stable solutions; Carbonium-ions; Spectrum

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