The crystal and molecular structure of naphthalene. II. Structure investigation by the triple Fourier series method

A triple Fourier series investigation of the naphthalene structure is described, based on the 612 structure factors listed in Part I. The series for the electron density has been evaluated at 54,000 points over the asymmetric crystal unit (half the chemical molecule), and the results are expressed by giving a number of sections through separate atoms at different levels, and also by giving a section through the plane of the molecule. From this map the bond lengths can be determined by direct measurement and are found to vary from 1.36 A. in the [alpha][beta] bond to 1.42 A. in the o[alpha] bond. The [beta][beta] bond and the central bond, oo, are both measured at 1.395 A. These figures are probably correct to within about 0.01 A., and appear to be in reasonably good agreement with the latest theoretical calculations. The rings are also found to be coplanar to within 0.01 A. The bridge value of the electron density varies in the different bonds; the electron distribution and the effect of the hydrogen atoms are briefly discussed.