Cyclopropane electronic charge density

Fig. 1.1. Shapes of molecules represented by envelopes of constant electronic charge density. The envelope shown has the value of 0.001 au. The molecules are (a)-(f) the normal alkanes from methane to hexane (g) isobutane (h) neopentane (i) cyclopropane (j) cyclobutane (k) formaldehyde, H2OK) (/) acetone, (CH3)2C=0. The intersections of the zero-flux interatomic surfaces with the envelope are shown in some cases. They define the methyl, methylene, hydrogen, and carbonyl groups. The isobutane molecule (g), for example, exhibits three methyl groups topped...

However, electron transfer-induced photoreactions in the presence of nucleophiles have attracted by far the greatest attention a rich variety of cyclopropane systems have been subjected to these reaction conditions. We will consider several factors that may affect the structure of the radical cations as well as the stereo- and regiochemistry of their nucleophilic capture. Factors to be considCTcd include (1) the spin and charge density distribution in the cyclopropane radical cation (the educt) (2) the spin density distribution in the free-radical product (3) the extent of... 

In chiral vinylcyclopropanes the chromophore can be viewed as inherently chiral, i.e. all the electronic transitions have simultaneously an electric (/i) and a magnetic (m) transition moment. For transoid or cisoid (indicated in broken lines below) arrangements the magnetic moments are generated by a circular displacement of electric charge density around the bond between the cyclopropane and the ethylenic moieties. The helical movement of electron density involves essentially p-atomic orbitals twisted relative to each... 

No chemical reactions have been observed which require the intermediacy of the B2-type cation radical. However, CIDNP experiments with 33 provide evidence for the existence of the unique structure of 33 in which two cyclopropane bonds are simultaneously weakened. It is noteworthy that spiroannelation with the fluorene ring causes a remarkable change in the distribution of the charge and odd electron densities in the ring of cyclopropane cation radicals. 

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