P-Electron system

This too is a Hiickel 4n + 2 p electron system (n = 2, this time) and shows quasi-aromatic stability stabilisation by aromatisation has again taken place, remarkably this time in a doubly charged carbanion (18). 

An initiator is required in this type of polymerisation. The polymerisation pro-ceeds through the intera-ction of the initiator with the p electron system of the vinyl monomers. 

NMR). Note the trans-trans-cis double bonds all bond angles can be 120 . [20]annulene presumably could become planar (it isn t quite) but since it is a 4n p electron system rather than a 4n + 2 system, it is not aromatic and the structure shows localized single and double bonds. 

Hosoya, H., and Murakami, M., Topological index as applied to p-electronic systems. II. Topological bond order. Bull. Chem, Soc. J, 48(12), 3512-3517 (1975),... 

It is seen that, for linearly ligating ligands acting on p electron systems, there is only one semiempirical AOM parameter... 

Ohno K (1967) Molecular orbital calculatimi of P electron systems. Adv Quant Chem 3 239-322... 

Direct UV detection is the most versatile detection method in CE and is implemented in every commercial CE system. Unfortunately, its use for carbohydrates detection is restricted because of their lack of conjugated p-electron systems and, consequently, the relatively low... 

In 1967, Itoh [10] and Wasserman et al. [11] independently found that the electronic ground state of bis(phenylmethylenyl)-w-phenylene. Structure (1), is the quintet state. On the basis of this finding, Mataga [12] proposed that the polymers, Structures (2) and (3), with the conjugated p-electron system,... 

Regardless of how many single-particle wavefiinctions i are available, this number is overwhelmed by the number of n-particle wavefiinctions ( ) (Slater detenninants) that can be constructed from them. For example, if a two-electron system is treated within the Flartree-Fock approximation using 100 basis fiinctions, both of the electrons can be assigned to any of the % obtained m the calculation, resulting in 10,000 two-electron wavefimctions. For water, which has ten electrons, the number of electronic wavefiinctions with equal numbers of a and p spin electrons that can be constructed from 100 single-particle wavefimctions is roughly... 

The so-called Flohenberg-Kolm [ ] theorem states that the ground-state electron density p(r) describing an A-electron system uniquely detemiines tlie potential V(r) in the Flamiltonian... 

Perdew J P and Zunger A 1981 Self-interaction correction to density-functional approximations for many-electron systems Phys. Rev. B 23 5048... 

Hiickel-type systems (such as Hilcfcel pericyclic reactions and suprafacial sigmatropic shifts) obey the same rules as for sigma electron. The rationale for this observation is clear If the overlap between adjacent p-electron orbitals is positive along the reaction coordinate, only the peraiutational mechanism can... 

Total spin den sity reflects th e excess probability of fin din g a versus P electrons in an open-shell system. Tor a system m which the a electron density is equal to the P electron density (for example, a closed-shell system), the spin density is zero. 

Perdew J P and A Zunger 1981. Self-Interaction Correction to Density-Functional Approximations for Many-Electron Systems. Physical Review B23 5048-5079. 

Neighboring group participation (a term introduced by Winstein) with the vacant p-orbital of a carbenium ion center contributes to its stabilization via delocalization, which can involve atoms with unshared electron pairs (w-donors), 7r-electron systems (direct conjugate or allylic stabilization), bent rr-bonds (as in cyclopropylcarbinyl cations), and C-H and C-C [Pg.150]

A. Mendizza and P. C. Milner "Materials Technology," ia Physical Design of Electronic Systems, Vol. II, Prentice-Hall, Inc., Englewood CHffs, N.J., 1970, Chapt. 5, p. 247. 

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