The gas-phase acidity of cyclopropene and simple alkyl derivatives: can they be measured?

✍ Scribed by Sangdon Han; Michael C. Hare; Steven R. Kass

• Book ID: 104432052
• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 155 KB
• Volume: 201
• Category: Article
• ISSN: 1387-3806
• DOI: 10.1016/s1387-3806(00)00216-5

✦ Synopsis

The gas-phase acidity of 3-methylcyclopropene (5) at the allylic position was explored computationally and experimentally. G2ϩ calculations indicate that ⌬HЊ acid ϭ 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) ϭ Ϫ1.54 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. (Int J Mass Spectrom 201 (2000) 101-108) © 2000 Elsevier Science B.V.