Z. Dega‐Szafran, I. Gąszczyk, D. Maciejewska
Jan 29, 2001
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Influential Citations
16
Citations
Journal
Journal of Molecular Structure
Abstract
Abstract N -(ω-carboxyalkyl)morpholine hydrochlorides, OC 4 H 8 N(CH 2 ) n COOH·HCl, n =1–5, were obtained and analyzed by 13 C cross polarization (CP) magic angle spinning (MAS) NMR, FTIR and PM3 calculations. The structure of N -(3-carboxypropyl)morpholine hydrochloride ( n =3) has been solved by X-ray diffraction method at 100 K and refined to the R =0.031. The crystals are monoclinic, space group P 2 1 / c , a =14.307(3), b =9.879(2), c=7.166(1) A , β =93.20(3)°, V=1011.3(3) A 3 , Z =4. In this compound the nitrogen atom is protonated and two molecules form a centrosymmetric dimer, connected by two N + –H⋯Cl − (3.095(1) A) and two O–H⋯Cl − (3.003(1) A) hydrogen bonds. 13 C CP MAS NMR spectra, contrary to the solution, showed non-equivalence of the ring carbon atoms. The PM3 calculations predict a molecular dimer without proton transfer for an HCl complex, while for an HBr complex an ion pairs with proton transfer, and reproduces correctly the conformation of both dimers but overestimates H-bond distances. Shielding constants calculated from the PM3 geometry of ion pairs gave a linear correlation with the 13 C chemical shifts in solids.