Study of Magic Number in Y-Aromaticity

In order to explain the strong basicity of guanidine, the concept of Y-aromaticity was proposed. As a typical compound of a Y-aromatic compound, a system in which three methylene of trimethylene methane is replaced by a chain conjugated system composed of n carbon atoms was proposed. The energy spectrum of the π-electron conjugated system of this compound was generally obtained within the Hückel approximation. The magic number of Y-aromatic compounds was determined by setting the conjugated system to a closed shell as a necessary condition for the energy stabilization of the system. The stabilization energies of several typical compounds were determined with the chain conjugated system as the reference system and the effectiveness of the magic number was investigated. The calculation of energy was done within the Hückel approximation. Although the tendency of magic number and energy stabilization did not perfectly agree, when the number of π electron system coincided with the magic number, energy destabilization tended to decrease.