Fractional ‘s’ character

Distance-dependent changes in hybridization Finally, with the diatomic NBO configurations established by Tables 3.15 and 3.17, the only remaining unknown parameter of the NBO Lewis-structure description is the hybridization X of hCT, Eq. (3.84a). For values of R around Rc. we can approximate the fractional s character of hCT by... 

The conjugated C-atoms of a fullerene respond to the deviation from planarity by rehybridization of the sp o and the p Jt orbitals, since pure p character of Jt orbitals is only possible in strictly planar situations ]56]. The electronic struchue of non-planar organic molecules has been analyzed by Haddon using the Jt orbital axis vector (POAV) analysis. For Cjq an average o bond hybridization of sp and a fractional s character of 0.085 (POAVl) or 0.081 (POAV2) was foimd ]59-63]. Consequently, the Jt orbitals extend further beyond the outer surface than into the interior of Cgg. This consideration implies, moreover, that fullerenes and, in particular, Cgg are fairly electronegative molecules [64, 65] since, due to the rehybridization, low-lying Jt orbitals also exhibit considerable s character. 

If s, px, py, pz orbitals are to be hybridized, and the fractional s character of three hybrids are specified, what remains to be specified before the hybrid set can be written explicitly ... 

The hybrids are sp3lBG, the fractional s character is 20.6 percent, and tional p character is 79.4 percent. 

If the interbond angle is 28 the fractional s character of the A-B hybrid a bond, population a, is (1 - cot20). If the third a orbital is occupied by... 

Although the coordinating character of trifluorophosphine and trialkyl phosphite can be assumed to be very similar, the observed coupling constants J( Co- P) differ substantially from one another. The smaller value found in the octahedral complex has therefore been accounted for by the larger fractional s-character of the Co-P bond in the trimethyl phosphite complex. (238)... 

Schulman and Newton employed the INDO method to develop a modified correlation (equation 5) between coupling constant and fractional s character. 

Numerous investigations have been directed toward elucidation of the factors affecting proton — C coupling. The general linearity between. /cm-h fractional s-character of the C hybrid atomic orbital has led to the conclusion that the Fermi contact term is essen-tially the sole contributor to the coupling, as suggested from the valence bond theory. The linearity between nd fractional... 

The fractional s-character of the P-H a bond was derived from spin densities on H, obtained by ESR spectra of PHg in three matrices, and is shown below, correcting a table given in [6] ... 

To make this bonding description quantitative, it is useful to describe an sp orbital in terms of its hybridization index, n, and its hybridization parameter, 2, defined as X = n. Now the fractional s character of the ith orbital is given by the expression 1 /(I + 2 ). For example, die fraction of... 

Consider again ethene and formaldehyde, this time analyzing the double bond in each as a two-membered ring. Calculate the fractional s character and hybridization parameter for the C-H bond in each. 

NMR. Estimate the fractional s-character of C(l) in its bond to C(3) of spiropentane, given the following information ... 

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