The gas-phase acidity of 3-methylcyclopropene (5) at the allylic position was explored computationally and experimentally. G2+ calculations indicate that ΔH°(acid) = 415.5 kcal/mol making 3-methyl-3-cyclopropenyl anion (6) an extremely strong base. This species is also predicted to be unstable with respect to electron loss (EA(3-methyl-3-cyclopropenyl radical) = -1.54 kcal/mol). A kinetic approach for determining the acidity of 5 using the hydroxide-induced desilylation of 3-methyl-3-trimethylsilylcyclopropene (the DePuy method) was employed but fails in this case because of an unanticipated rearrangement. This raises the question: Can the acidity of cyclopropene and its simple alkyl derivatives be measured? Positive and negative responses to this question are given and discussed. (C) 2000 Elsevier Science B.V.
|Original language||English (US)|
|Number of pages||8|
|Journal||International Journal of Mass Spectrometry|
|State||Published - 2000|
Bibliographical noteFunding Information:
Support from the National Science Foundation, the donors of the Petroleum Research Foundation, as administered by the American Chemical Society, the Minnesota Supercomputer Institute, and the University of Minnesota—IBM Shared Research Project are gratefully acknowledged. We also thank Dana Reed for some experimental assistance.
- Cyclopropenyl anions
- G2 theory
- Ion cyclotron resonance
- Kinetic method