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Figure 6 Projection of the acetate salt viewed down b. The hydrated tartrate salts are similar; the structures not shown retain a bilayer form with hydrogen-bonded interactions in the core of the bilayer and the bilayers linked by further hydrogen bonding into sheets. Interlayer interactions are face-to-edge on both sides. Overall it is clear that the molecular packing in many of these solids reflects the amphiphilic nature of the molecular structure of ephedrine itself, with the almost ubiquitous existence of a molecular bilayer, in which the polar hydroxyl and protonated amino functionalities are sandwiched between the nonpolar aromatic moieties. R -factors based on F 2 are statistically about twice as large as those based on F , and R – factors based on ALL data will be even larger.
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The nomenclature used to describe the salt forms of the sulfonic acids is that used widely in the pharmaceutical industry, with besylate representing the counterion benzenesulfonic acid, edisylate ethanedisulfonicesylate ethanesulfonicmesylate methanesulfonic and tosylate toluenesulfonicrespectively.
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Ephedrine neutral base and hemihydrate 5. These layers are then interlinked by aromatic face-to-edge contacts. Refinement of F 2 against ALL reflections. Refinement top Refinement on F 2 Secondary atom site location: In the case of the disulfonate edysilate, each anion now bridges two ephedrine cations via hydrogen bonds and coulombic interactions which, together with methyl—aromatic close contacts create sheets interdigitated with face-to-edge interactions.
In a few cases the size and hydrophobicity of the counterion disrupts this behaviour. Finally in the tosylate, the bilayers again comprise both anions and cations.
It is clear that the packings observed incorporate, as expected, both bilayer structures of the ions and the two conformations of the ephedrine ion. The mesylate follows a now familiar pattern in which coulombic and hydrogen-bonded interactions from sulfonate O atoms to silkroaf and hydroxyl groups create an layer, with layers interdigitated and held by aromatic face-to-edge contacts.
Black b and Ron J. Special details top Geometry. For all compounds, program s used to solve structure: H atoms treated by a mixture of independent and constrained refinement.
These workers were concerned with understanding the structural basis of the chiral resolution process and the relation between solution and crystal structures, respectively, and their studies revealed two conformations of ephedrine in structures based on bilayer packings.
Our new structures do not appear to support their notion that the extended conformation is associated with face-to-edge aromatic interactions. These sheets are stacked along the a axis and held by face-to-edge methyl—phenyl and phenyl—phenyl close contacts.
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From the previous studies Leusen et al. Collect Nonius BV, ; cell refinement: Structures of the acetate, adipate, maleate, malonate, glycolate, malate and tartrate were solved.
This study has provided the structures of 17 salts of the base ephedrine, enabling for the first time the opportunity to compare and contrast the impact of various factors on the crystal packing of a single molecular entity.
Received 17 October ; accepted 3 April The aromatic nature of the besylate totally destroys the ephedrine bilayer and creates Fig. The case of the glycolate represents a further complication, being a hydroxy acid. Ten structures exhibit the extended form and nine the folded form.
The malate structure is a very similar bilayer structure with the hydrogen bonding creating a sheet. Sulfonic acids The mesylate follows a now familiar pattern in which coulombic and hydrogen-bonded interactions from sulfonate O atoms to amino and hydroxyl groups create an layer, with layers silroad and held by aromatic face-to-edge contacts.
In the discussion below we describe the details of some of the specific structures, while here we make some general observations. In earlier studies Leusen et al. The bilayers are then stacked along c by silkrosd contacts between the interdigitated aromatic rings.
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This is 1.3366 expected from the previously solved salt structures Leusen et al. Structure solution was performed either with SIR 92 Altomare et al.
Figure 10 Projection of the besylate salt viewed down c. Crystal packing and hydrogen bonding analysis. Given the previous calculations Leusen et al. Here the extended non-polar [— CH 2 4 —] chain interacts with alternate phenyl rings and the bilayer structure is lost, as seen in Fig.