Structural and conformational analysis of some organics molecules

Molecular and crystal structure of `2-Methoxy-4-[(5-oxo-2-phenyl-4,5-dihydro-1,3-oxazol-4-ylidene)methyl]phenyl 4-methylbenzenesulfonate` (C(24)H(19)NO(6)S) and `1,3-Di-3-pyridyl-2,3-dihydro-1H-naphth[1,2-e] [1,3] oxazine' (C(22)H(17)N(3)O)have been determined by single crystal X-ray diffraction study.The compound, C(24)H(19)NO(6)S, which was crystallized in triclinic system is related to P-1 space group. The structure was solved by direct methods and refined to a final R ?equals? 0.050 for 2745 reflections with I ?greater than? 2sigma(I). The molecule adopts the Z-configuration. The oxazolone ring is approximately coplanar with 2-phenyl and methoxyphenyl rings. The crystal structure is stabilized by C-H?N type intra-molecular and C-H?O type weak inter-molecular interactions. Pairs of molecule are linked into dimers through weakC-H?O hydrogen bonds in the crystal structure. In addition, to investigate conformational flexibility of the molecule, the selected torsion angle is varied from ?minus? 180 degrre to ?plus? 180 degree in every 10 degree separately and molecular energy profile is calculated and analyzed. It is concluded that where the profile has minimums, there are intra-molecular weak interactions, such as H-bonding.The compound, C(22)H(17)N(3)O, is in the monoclinic crystal system and P2(1)/c space group. The structure was solved by direct methods and refined to a final R ?equals? 0.041 for 1786 reflections with I ?greater than? 2sigma(I). In the molecule, the oxazine ring has a half-chair conformation. The dihedral angles made by the best least-squares plane through the planar part (O-C-C-C-N) of the oxazine ring with the mean planes of the pyridine rings (N2/C1-C6) and (N3/C6-C10) are 72.14(6) degree and 35.44(7) degree, respectively. The molecule has two stereogenic centers at the oxazine carbons C21 and C22 , RS and SR. In the crystal structure, intermolecular N-H?N hydrogen bonds link the molecules to form an infinite one-dimensional polymeric chain along b-axis. Graph set notation of polymeric chain is C(6).