Hexamethylenetetramine crystal structure

Working first with Polanyi, Weissenberg, and Brill, and later as the leader of the Textile Chemistry Section, Mark successively published papers on the crystal structures of hexamethylenetetramine, pentaerythritol, zinc salts, tin, urea, tin salts, triphenylmethane, bismuth, graphite, sulfur, oxalic acid, acetaldehyde, ammonia, ethane, diborane, carbon dioxide, and some aluminum silicates. Each paper showed his and the laboratory s increasing sophistication in the technique of X-ray diffraction. Their work over the period broadened to include contributions to the theories of atomic and molecular structure and X-ray scattering theory. A number of his papers were particularly notable including his work with Polanyi on the structure of white tin ( 3, 4 ), E. Wigner on the structure of rhombic sulfur (5), and E. Pohland on the low temperature crystal structure of ammonia and carbon dioxide (6, 7). The Mark-Szilard effect, a classical component of X-ray physics, was a result of his collaboration with Leo Szilard (8). And his work with E. A. Hauser (9, 10, 11) on rubber and J. R. 

In a molecular crystal, the idealized symmetry of the molecule is often not fully expressed in other words, the molecule occupies a site of lower point symmetry. For example, in the crystal structure of naphthalene, the CsHio molecule (idealized symmetry Z>2h) is located at a site of symmetry I. On the other hand, the hexamethylenetetramine molecule, (CH2)6N4, retains its T symmetry in the crystalline state. Biphenyl, C6H5 —C6H5, which exists in a non-planar conformation with a dihedral angle of 45° (symmetry >2) in the vapor phase, occupies a site of symmetry I in the crystalline state and is therefore completely planar. 

Adamantane, a structural analog of hexamethylenetetramine, crystallizes at room temperature in the cubic space group Fm3m with ac = 944.5 pm and Z = 4. The structure is disordered, not ordered in space group F43m (no. 216, multiplicity = 96) as described in a previous report. The cubic close-packed arrangement of (CH2)6(CH)4 is favored over the body-centered cubic structure... 

Figures 20.4.4(a) and 20.4.4(b) illustrate the crystal structure of the 1 1 complex of tetraphenylmethane and carbon tetrabromide. The nodes comprise C(C6H5)4 and CBr4 molecules, and the each linking rod is the weak interaction between a Br atom and a phenyl group. The hexamethylenetetramine-like structural unit is outlined by broken lines. Figures 20.4.4(c) and 20.4.4(d) show the crystal structure of tetrakis(4-bromophenyl)methane, which has a distorted diamondoid network based on the hexamethylenetetramine building unit. If the synthon composed of the aggregation of four Br atoms is considered as a node, then two kinds of nodes (Br4 synthon and quatenary C atom) are connected by rods consisting of p-phenylene moeities.

In the crystal structure of [Ag C(4-C6H4CN)4 ]BF4 xPhNCh, the structural unit is of the hexamethylenetetramine type (Fig. 20.4.7). The nodes are Ag atoms and C(4-C6H4CN)4 molecules, and the rods are CN- -Ag coordination bonds. The void space is filled by the nitrobenzene guest molecules and BFJ ions. 

The X-ray crystal structures of the quinuclidine and hexamethylenetetramine adducts show very long Os—N bonds (2.37 and 2.42 A respectively) while the symmetry of the 0s04 unit is little disturbed the Os—O bond lengths are between 1.697 and 1.722 A, and the O(axial)Os0(equatorial) angle of 100.6° is close to the tetrahedral angle of 109-47° (Figure 33).634... 

Fig. 8. Two nearly spherical molecules, adamantane and hexamethylenetetramine, for which crystal structures are different.

The first determination of the molecular architecture of a compound of carbon was made in 1923, when the structure of the cubic crystal hexamethylenetetramine, C6Hu N4, was determined by x-ray diffraction. 

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