Structural studies of benzene derivatives. I. Refinement of the crystal structure of p-phenylenediamine dihydrochloride

Abstract

The crystal structure of p-phenylenediamine dihydrochloride, determined by Chandrasekaran 1,4cta Co'st. (1969), B25,369-374] from photographic data, has been refined by full-matrix least squares to a final R of 0.0276, with 1281 independent non-zero reflexions measured on an automated single-crystal diffractometer. Crystals are tdclinic, space group P1, with a = 8.680 (3), b = 5.835 (3), c = 4.333 (2) ,A,, a = 99.86 (9), fl = 96.28 (4), y = 110.19 (9) °, Z = 1. The C hexagon has D2h (mmm) symmetry within experimental error. The distortions from D6h (6/mmm) symmetry are highly significant, and testify to the strong o-electron-withdrawing character of the substituent. The internal angle at the ipso carbon, aNH;, is 121-9 (l) °.

Structural studies of benzene derivatives. II. Refinement of the crystal structure of p-nitrobenzoic acid

“…Domenicano, Foresti Serantoni & Riva di Sanseverino, 1977). In the present paper we describe the molecular structure of crystalline p-nitrobenzoic acid, as obtained from a new X-ray diffraction study.…”

“…As a development of a research programme on the deformations, induced by substitution, of the geometry of the benzene ring (Domenicano, Vaciago & Coulson, 1975a,b: Domenicano, Mazzeo & Vaciago, 1976 we have started accurate experimental work to determine the molecular structures of a number of benzene derivatives (Colapietro, Di Rienzo, Domenicano, Foresti Serantoni & Riva di Sanseverino, 1976; * Part I: Domenicano, Foresti Serantoni & Riva di Sanseverino (1977). Domenicano, Foresti Serantoni & Riva di Sanseverino, 1977).…”

On the Order-Disorder Phase Transformation of Anilinium Halides. III.

“…7 one can see that in both orientations the ring is practically in an eclipsed position to one H atom of the -NH3® group. Such an eclipsed configuration is known from several crystal structure studies of anilinium compounds [18], [24]. The resulting eclipse-angle C-C-N is up to 2° larger than the staggered one.…”

1-(2,3-Dideoxy-erythro-β-D-hexopyranosyl)cytosine: an example of the conformational and stacking properties of pyranosyl pyrimidine nucleosides. A crystallographic and computational approach

“…Thus, conclusions drawn from these parameters only remain valid within a certain approximation. A second and more appropriate approach for the calculation of mean bond lengths or angles simply involves the calculation of the weighted means of the parameters using the formulae of Domenicano, Serantoni & Riva di Sanseverino (1977). Having performed this for all the pyranose bond lengths, angles and torsion angles, the results are tabulated in Table 2.…”