18440-28-3Relevant academic research and scientific papers
1H and 13C Nuclear Magnetic Resonance Study of 1,3-Dipyridylthioureas for Chemical Shift Assignments and Conformational Analysis
Sudha, L. V.,Sathyanarayana, D. N.,Bharati, S. Narasimha
, p. 474 - 479 (1987)
A study of molecular conformation by 1H and 13C NMR methods of three 1,3-dipyridyl thioureas namely, 1,3-di(2-pyridyl)thiourea (1), 1,3-di(3-pyridyl)thiourea (2), 1-(2-pyridyl)-3-(3-pyridyl)thiourea (3), and also of 1-phenyl-3-(2-pyridyl)thiourea (4) and 1,3-diphenylthiourea (5), included for the sake of coparison, was carried out.Evidence was obtained that 3 and 4 exist in solution solely in one form, in an internally hydrogen bonded E,Z conformation, whereas 1, 2 and 5 exist in two (or more) rotamer forms.The data reveal an interesting dynamic exchange phenomenon occuring in 1 between two intramolecularly hydrogen bonded conformers.The 1H and 13C chemical shifts, 1H,1H and 13C,1H coupling constants are reported.The 13C and 1H chemical shifts are correlated with the electron densities calculated by the CNDO method. KEY WORDS 1H NMR 13C NMR 1,3-Dipyridylthioureas Conformation.
Molecular Conformation of N,N'-Diarylthioureas: an Assessment by 1H NMR and Infrared Spectroscopy
Sudha, L. V.,Manogaran, S.,Sathyanarayana, D. N.
, p. 591 - 596 (2007/10/02)
Several N,N'-dipyridyl- and N-phenyl-N'-pyridyl-thioureas were examined in different solvents at various temperatures by 1H NMR in order to study their conformational properties.The influence of concentration and the methyl substituent in the pyridine ring on the chemical shifts of the NH and pyridine groups was investigated.The observed chemical shifts are analysed in terms of the conformational properties of the molecules.Free energy barriers to the internal rotation about the C-N bonds have been determined.Infrared spectra have been measured to supplement the NMR studies.Intramolecular hydrogen bonding played a major role in the preferred conformation of pyridylthioureas.The data further revealed an interesting dynamic exchange phenomenon occuring in symmetric N,N'-dipyridylthioureas between two intramolecularly hydrogen bonded conformers.
