On the Strain Energy in Cyclopropene and the Heat of Formation of the C₃H₃⁺ Ion

Photochemical Valence Isomerization to High Energy Products—Bicyclobutanes and Oxabicyclobutanes†

“…For example, consider the following formal ring opening reactions [13] and [14], where we equate the strain energy and the endothermicity of the cyclopropene and cyclopropane cyclizations. From the enthalpies of formation of cyclopropene (101), ethylene (102) and of 1,4‐pentadiene (76), we deduce the strain energy of cyclopropene to be 225 kJ mol −1 . Likewise, from the enthalpy of formation of cyclopropane (71), ethane (a consensus of the values from refs.…”

Re-Examination of Some Carbocations. Structures, Energies, and Charge Distributions

“…We assembled the needed apparatus and measured the heat of combustion of cyclopropene by flame calorimetry, allowing us to calculate the heat of formation. In collaboration with Lossing, the energy of the cation was estimated via mass spectrometry . The result indicated that cyclopropenium ions were stabilized by electron delocalization.…”

“…17 Treatment of a solution of cyclopropene with triphenylmethyl chloride in CCl 4 led to a rapid reaction and an apparent hydride transfer because triphenylmethane was formed. 18 There was, however, no indication of a cyclopropenyl cation, but another product of the reaction was a polymer whose NMR spectrum had bands characteristic of cyclopropane rings, suggesting that the cation had been formed but reacted more rapidly with cyclopropene than the triphenylmethyl cation.…”

“…However, first, we shall examine the question of why dialkyl substitution leads to remarkable stabilization of the cyclopropenium ion. Whereas the parent ion is not stable in water, , the di- n -propylcarbenium ion is quite stable in 1 N HCl . This study allows an estimate of the delocalization energy (DE) of the cyclopropenium ion, that is compared with those of the cyclopentadienide anion and the cycloheptatrienyl cation.…”

The reactions of 1,2‐dioctylcyclopropene with silver nitrate

“…With cis-alkenes and strained cyclic olefins, relief of strain by slight twisting of the R groups around the double bond out of a planar configuration is used to explain their increased complexing ability over trans-alkenes and unstrained eyeloolefins. Cyclopropenes are the most strained eycloolefins known(26) and the relief of this strain by further reaction of intermediate 20 is the driving force behind the silver nitrate-cyelopropene reaction.…”