Molecule diamagnetic susceptible

Values of the diamagnetic anisotropy of benzene and other aromatic hydrocarbon molecules are calculated on the basis of the assumption that the p, electrons (one per aromatic carbon atom) are free to move from carbon atom to adjacent carbon atom under the influence of the impressed fields. When combined with the assumed values for the contributions of the other electrons (-2.0X 10-6 for hydrogen, —4.5 X10 c for aromatic carbon, — 6.0XlO-6 for aliphatic carbon) these lead to principal diamagnetic susceptibilities of molecules in approximate agreement with the available experimental data. The diamagnetic anisotropy of graphite is also discussed. 

Measured values of the diamagnetic susceptibility of the noble gases correspond to reasonable values of Sr2. For polyatomic molecules the interpretation of the diamagnetic susceptibility in terms of structural features is in general uncertain, and this property has not been found to be valuable in structural chemistry. 

Some diamagnetic crystals (graphite, bismuth, naphthalene and other aromatic substances) show prohounced diamagnetic anisotropy. The observed anisotropy of crystals of benzene derivatives correspond to the molar diamagnetic susceptibility —54 X 10 with the field direction perpendicular to the plane of the benzene ring and —37 X lO"6 with it in the plane. This molecular anisotropy has been found to be of some use in determining the orientation of the planes of aromatic molecules in crystals.1... 

To further appreciate this view, we present in Scheme 20 the computed A quantity of He and benzene.6 This quantity is the difference between the diamagnetic susceptibilities (%) of the molecule and a suitable localized reference, defined in eq 6... 

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