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STRUCTURE AND CRYSTAL PACKING OF THE ORGANIC SALT 2-(DIMETHYLAMINO)-5-METHYL-1,3-THIAZOLIUM 1,1,2,3,3-PENTACYANOPROPENIDE, C6H11N2S+.C8N5-
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X-ray variable temperature study on proton transfer and polymorphism in 3-(p-chlorophenyl-)-1,5-diphenylformazan
No full textCrystal and Molecular Structures of 2,6-cis-Dimethylpiperidyl-N-phenylacetamidine and 2,6-cis-Dimethylpiperidyl-N-phenyl-2,2-dimethylpropionamidine. An X-ray Crystallographic Investigation of the C(sp2)-N(piperidyl) Bond
No full textThe single crystal X-ray analyses of 2, 6-cis-dimethylpiperidyl-N-phenylacetamidine (MA) and 2, 6-cis-dimethylpiperidyl-N-phenyl-2, 2-dimethylpropionamidine (TBA) are described. MA crystallizes in the space group P2 1\c with four molecules in the unit cell of dimensions a = 10.238 (2), b = 10.189 (2), c = 12.875 (3) Å. and β = 95.82 (2)°. The structure was solved and refined from 1401 unique observed reflections collected on an automated four-circle diffractometer to final values of the discrepancy indices of R = 0.046 and Rw = 0.058. TBA crystallizes in the space group P21\c with eight molecules in the unit cell of dimensions a = 8.470 (2), b = 16.095 (3), c = 24.900 (4) Å, and β = 96.29 (2)°. From 2633 unique observed reflections similarly collected the structure was solved and refined to final values of the discrepancy indices of R = 0.061 and Rw = 0.074. The structure analyses show, in agreement with 13C NMR spectroscopic data, that ihe two molecules adopt different conformations around the C(sp2)-N(piperidyl) bond, the amidinic group and the piperidyl ring being approximately coplanar in MA and orthogonal in TBA, respectively. The comparison of the present data with the data in the literature, supported by nonbonded intramolecular potential energy calculations and IN DO calculations, allows clarification of the relationship among the torsion angle around the C-N bond, the bond distances in the amidinic group, the pyramidality of the N (piperidyl) atom and the conformation of the 2, 6-m-methyl groups in the piperidyl ring. © 1979, American Chemical Society. All rights reserved
Tautomerism in Bis(oxazolines): an Experimental and Theoretical Study of Proton Transfer in 1,1-Bis[4,4-dimethyl-1,3-oxazolin-2-yl]ethane
No full textThe serendipitous isolation of an unusual protonated bis(oxazoline) prompted us to discuss the role of H+ on the kinetics and thermodynamics of the equilibrium between its ketimine and enamine forms. X-ray diffraction analysis revealed that the protonated bis(oxazoline) is in the Z-enamine form, the unipositive charge is counterbalanced by [(FeCl3)(2)O](2-) and [FeCl4](-) anions. DFT calculation at the BP86/TZVP level showed that relative stability of enamine tautomer versus ketimine tautomer increases with the protonation of the nitrogen atom of the oxazolidine ring. At the same time, the barrier energy of tautomerism decreases
N-[1-PHENYL-2(R)-PROPYL]-2-CHLOROADENOSINE - AN ACTIVATING AGENT OF THE ADENOSINE A2 RECEPTOR
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