Barriers to internal rotation around the C-N bond in 3-(o-aryl)-5-methyl-rhodanines using NMR spectroscopy and computational studies. Electron density topological analysis of the transition states.
We have investigated the pairs of rotational isomers for six 3-(o-aryl)-5-methyl-rhodanines (Z = H, F, Cl, Br, OH, and CH3) using NMR spectroscopy and density functional theory (DFT) calculations. Electron density topological and NBO analysis has demonstrated the importance of non-covalent interactions, characterised by (3, -1) bond critical points (BCPs), between the oxygen and sulfur atoms on the thiazolidine ring with the aryl substitutents in stabilizing the transition states. The energetic activation barriers to rotation have also been determined using computational results; rotational barriers for 3-(o-chlorophenyl)-5-methyl-rhodanine (3S) and 3-(o-tolyl)-5-methyl-rhodanine (6S) were determined experimentally based on NMR separation of the diastereoisomeric pairs, and the first-order rate constants used to derive the value of the rotational barrier from the Eyring equation.
Department of Chemistry, Bogazici University, Bebek, Istanbul, Turkey.
Yeliz
Y
Aydeniz
Funda
F
Oguz
Arzu
A
Yaman
Aylin Sungur
AS
Konuklar
Ilknur
I
Dogan
Viktorya
V
Aviyente
Roger A
RA
Klein
D003198:Computer Simulation; D004583:Electrons; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008956:Models, Chemical; D008968:Molecular Conformation; D012236:Rhodanine / Q000031:analogs & derivatives* / Q000737:chemistry*; D012399:Rotation; D013816:Thermodynamics
D012236:Rhodanine