Robert D. Rosenstein

The crystal structure of ribitol

Residual electron density During the refinements of this structure no attempt was made to pick out one particular oxygen atom as carrier of the negative charge of the anion. The form factor was always the one given in International Tables for X-ray Crystallography (1962) for the free oxygen atom. One extra electron is thus present in the anion in addition to those included in the calculations, and to conclude the analysis, a difference Fourier synthesis was evaluated. After omission of the uncertain 400 and 004 reflexions, the residual electron density in the region of the ascorbate anion is shown in Fig.4. These maxima are clearly the largest in the unit cell, and some of them fall in the space between the carbon and oxygen atoms. This result is quite similar to that for ascorbic acid, but whether the peaks adjacent to the O(2), 0(3) and 0(4) atoms outside the bond area have relevance to the extra electron is questionable because of the low significance of such peaks in the present case. The author would like to express his gratitude to Det Norske Videnskaps-Akademi for a grant, and also to J. Solbakk, P. Groth, B. Klewe, F. Gram and T. Dahl for the use of their computer programs. He is also indebted to Professor S. Furberg for illuminating discussions.