Reflection, diatropic

Fig. 31. A fibre diagr im. Schematic, projection of fibre-axis, equator with paratropic reflections, diatropic reflections.

From Equation 8 the value of Kc can be obtained and it varies from 238 to —1. The value of Fc, which is the meaningful term, is 134 ppm per electron. It can therefore be seen that the shift/charge relationship (Kc) in the 4nrc systems is less sensitive to charge than the Kc value of the diatropic (4n + 2) ir-systems, and reflects the special electronic properties of the 4nrt-anion series. An intrinsic property of the (4n + 2) 71-series is the wide HOMO-LUMO gap (AE), while the 4nTt-series are characterized by a narrow HOMO-LUMO gap 40). These differences should always be taken into account when the spectrospic behaviour of the different series is considered 35,36). 

Magnetic effects result from aromatic diatropic and paratropic antiaromatic ring currents and are reflected in H NMR chemical shifts, magnetic susceptibility exalation, and nucleus-independent chemical... 

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