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Investigations of 1,1,2,3,3-pentamethylenepropane derivatives
Abstract
The first systematic experimental study of diradical 1,1,2,3,3-pentamethylenepropane (PMP) systems has been carried out. A series of PMP precursors based on the bicyclo (3.1.0) hexan-3-one framework was synthesized. The precursors were photolyzed and thermolyzed with the goal of generating a derivative of PMP. Evidence for the formation of a PMP diradical came when 2,4-bis(phenylmethylene)-exo-6-methyl-bicyclo (3.1.0) hexan-3-one (84) was found to epimerize photochemically and thermally. The thermodynamic parameters, E$\sb{\rm a}$ = 30.99 $\pm$ 0.51 kcal/mol and log A = 11.20 $\pm$ 0.27, were calculated for the range 164.3-204.5$\sp\circ$C. These values are evidence for a PMP intermediate in comparison to the predicted values obtained from a Benson analysis and the parameters for similar known cyclopropane thermal rearrangements. Two experimental efforts to identify directly the reaction intermediate were inconclusive. However, the kinetic analysis is only consistent with PMP formation. We unsuccessfully attempted to observe spectroscopically the PMP-like species by low-temperature ESR and UV-Vis. Olefinic trapping studies also proved to be inconclusive in identifying a PMP-like species. The cyclic bis-enamines (118, 119, 121, 122) were found to phosphoresce brightly upon photolysis in frozen matrix at 77K. This phenomenon is unique to the bis-enamines as the mono-enamine (120) failed to phosphoresce under identical conditions. The UV absorption, fluorescence, the phosphorescence spectra for the bis-enamines are reported.
Subject Area
Organic chemistry
Recommended Citation
Kearley, Mark L, "Investigations of 1,1,2,3,3-pentamethylenepropane derivatives" (1992). Doctoral Dissertations Available from Proquest. AAI9219455.
https://scholarworks.umass.edu/dissertations/AAI9219455