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1 H and 13 C nuclear magnetic resonance study of 1,3‐dipyridylthioureas for chemical shift assignments and conformational analysis
Author(s) -
Sudha L. V.,
Sathyanarayana D. N.,
Bharati S. Narasimha
Publication year - 1987
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260250603
Subject(s) - chemistry , thiourea , conformational isomerism , chemical shift , cndo/2 , crystallography , hydrogen , proton nmr , resonance (particle physics) , molecule , computational chemistry , stereochemistry , organic chemistry , atomic physics , physics
A study of molecular conformation by 1 H and 13 C 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 comparison, 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 occurring in 1 between two intramolecularly hydrogen bonded conformers. The 1 H and 13 C chemical shifts, 1 H, 1 H and 13 C, 1 H coupling constants are reported. The 13 C and 1 H chemical shifts are correlated with the electron densities calculated by the CNDO method.