P2!/c space group

The bis(hydrogensquarate) dihydrate salt of (4-pyridylmethyl)amine was the first diprotonated form of (4-pyridylmethyl)amine to be refined crystallographically. Until now, only a monoprotonated form, stabilized as the hydrochloride (QANWOS [268]) was known. The compound crystallizes in the monoclinic P2/c space group and exhibits Z = 6. The dication, two solvent molecules, and both anions form a 3D network by intermolecular interactions of type NH3+---OH2 (2.816 A), NH3+---0 (2.807, 2.813 A), and N+H---0 (2.659 A). The hydrogensquarates form a new structural motif of isolated a-joined anions (0H---0 (2.551 A) reported for first time in the literature. These pairs of anions are connected to one another by the interactions with solvent water molecules, by means of HOH---0 (2.521,2.800,2.697,2.781 A) as well as H0H-"0H2 (2.753 A) hydrogen bonds (Figures 4.18 and 4.19). 

Unit cell parameters were obtained from a study conducted on a single crystal of the material. The crystal class was monoclinic within the P2, or P2,/m space groups. The unit cell was characterized by the following lattice parameters a = 9.686(2) A, 6 = 8.792(4) A, c = 10.085(6) A, p = 92.33(4)°. 

Cane sugar is generally available ia one of two forms crystalline solid or aqueous solution, and occasionally ia an amorphous or microcrystalline glassy form. Microcrystalline is here defined as crystals too small to show stmcture on x-ray diffraction. The melting poiat of sucrose (anhydrous) is usually stated as 186°C, although, because this property depends on the purity of the sucrose crystal, values up to 192°C have been reported. Sucrose crystallines as an anhydrous, monoclinic crystal, belonging to space group P2 (2). 

As a result of having two chiral centers, four stereoisomers of ascorbic acid are possible (Table 1) (Fig. 2). Besides L-ascorbic acid (Activity = 1), only D-araboascorbic acid (erythorbic acid (9)) shows vitamin C activity (Activity = 0.025-0.05). The L-ascorbic acid stmcture (1) in solution and the soHd state are almost identical. Ascorbic acid crystallizes in the space group P2 with four molecules in the unit cell. The crystal data are summarized in Table 2. 

AlSCl has an orthorhombic structure, with the lattice constants a - 8.09, b = 10.52, c = 3.86 A, andZ = 4. It is probably isotypic with SbSCl and BiSCl, crystallizing in a layer type of lattice (157) (see Section XII,C,5). The selenide halides are monoclinic, with the probable space-group P2,/m. The lattice constants are given in Table XVII. The constancy of the b parameters for all three compounds suggests the general presence of an Al-Se chain extending in that direction (266). 

With the chemical structure of PbTX-1 finally known and coordinates for the molecule available from the dimethyl acetal structure, we wanted to return to the natural product crystal structure. From the similarities in unit cells, we assumed that the structures were nearly isomorphous. Structures that are isomorphous are crystallographically similar in all respects, except where they differ chemically. The difference between the derivative structure in space group C2 and the natural product structure in P2. (a subgroup of C2) was that the C-centering translational symmetry was obeyed by most, but not all atoms in the natural product crystal. We proceeded from the beginning with direct methods, using the known orientation of the PbTX-1 dimethyl acetal skeleton (assuming isomorphism) to estimate phase... 

NitPy C C-H). In the solid state, the NitPy(C C-H) molecules (space group P2,/n crystallize in chains via a hydrogen bond -CM3-H- -0-N- (Figure 4), with positive intrachain magnetic coupling [16], A single crystal (5.0 x4.5 x 1.7 mm3) was... 

Fig. 17. Stereoview of the inclusion structure formed by host II with diethyl ether (crystal data a = 9.092, b = 24.809, c = 9.135 A, p = 102.60°, space group P2,) (taken from Ref.4I))...

The SnCl2 adduct 20d crystallizes in the monoclinic space group P2,/c and shows only slight variations in the Sn-P distances (av. 

The molecular structure of 1,2,9,10-tetrastanna[2.2]paracyclophane 22 was determined by the X-ray diffraction method. The crystal belongs to the space group P2,/a, and the data collection was carried out at 13°C. The ORTEP drawing of 22 is shown in Fig. 8. 

A change in space group has also been observed for [Fe(3-OEt-salA-PA)2]C104-C6H5X (X=C1, Br) [128]. The space group for the chlorobenzene derivative is P2 /c at 296 K and converts to P2i/a at 158 K. A similar trans-... 

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