February 16, 1938

Dr. Melvin S. Newman

Department of Chemistry

Ohio State University

Columbus, Ohio

Dear Dr. Newman:

I am glad to learn that you are contemplating the synthesis of coronene. There are two problems relating to the structure of polycyclic aromatic hydrocarbons which can be attacked more satisfactorily with use of coronene tha[n] with related substances. The first of these, involving the configuration of the molecule and in particular the values of interatomic distances can be attacked by the study of the structure of the coronene crystal with x-rays. Coronene is especially useful because of the high symmetry of the molecule. The second, bearing on the diamagnetic anisotropy of the substance can be attacked by making measurements on the crystal. Here, too, the high symmetry is important in that it permits the solution of the secular equation for the susceptibility, as discussed in the accompanying reprint.

I believe that the measurement of the heat of combustion of coronene by the standard method involving the solid would be useful. The accurate methods based on heats of hydrogenation of vapors as applied by Kistiakowsky probably could not be used because of the low vapor pressure of the substance.

Sincerely yours,

Linus Pauling

LP/C