Jc. Walton et L. Whitehead, gamma-dissociations of 3-alkylbicyclo[1.1.1]pent-1-yl radicals into [1.1.1]propellane and alkyl radicals: verification of a theoretical prediction, PCCP PHYS C, 1(7), 1999, pp. 1399-1404
The gamma-dissociations of 3-substituted bicyclo[1.1.1]pent-1-yl radicals a
nd cyclobutyl radicals were investigated by ab initio SCF MO (HF, MP2, MP3
and MP4/6-31G*) and density functional methods (B3LYP/6-31G*). The transiti
on states were found to resemble the product alkyl radical and [1.1.1]prope
llane or bicyclo[1.1.0]butane. Calculated endothermicities and energy barri
ers were comparatively low for loss of the t-butyl radical from the 3-t-but
ylbicyclo[1.1.1]pent-1-yl radical, which suggested that this dissociation w
ould be significant under laboratory conditions. The dissociation was verif
ied experimentally by means of the reaction of 1-iodo-3-t-butylbicyclo[1.1.
1]pentane with tributyltin hydride. Arrhenius parameters for this dissociat
ion were determined by end product analysis. The SCF MO and density functio
nal calculations resulted in much higher endothermicities and energy barrie
rs for gamma-dissociations of cyclobutyl radicals, hence neither the format
ion of bicyclo[1.1.0]butane nor alkyl radical addition to this bicyclic com
pound was predicted to be important.