McConnel equation

Analyze the hyperfine coupling in the spectrum of the butadiene radical anion given in Fig. 12.PI I. What is the spin density at each carbon atom according to the McConnell equation ... 

There is a relationship (the McConnell equation) between the unpaired electron density on a given atom and the polarization interaction with each attached proton ... 

By using the McConnell equation and the experimental H-coupling constants, it is possible to calculate the spin density at the carbon atoms bearing protons. The missing parameter which is needed to calculate the spin density at the P atom has been estimated by Thomson and Kilcast... 

We now consider some applications of the McConnell equation (8.126), using Hiickel MO theory to estimate pw C. For the methyl radical, pw>c l, and aH is predicted to be - 23 G, in agreement with the observed proton coupling constant (Fig. 8.15). 

Figure 7. GIAO-calculated shielding increment (Ao) of "ghost atoms" (triangles) and the McConnell equation-calculated shielding increment (circles) 2.0 A above ethene vs. lateral distance from the center of the carbon-carbon double bond.

The McConnell equation (Equation 1.17) shows the relationship of the observed coupling constant (aH) to the unpaired spin population on the adjacent carbon atom (pc)-... 

It should be noted that there are a number of assumptions and approximations in the derivation of the McConnell equation. These include ... 

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