CHELATES OF BETA-DIKETONE DERIVATIVES .15. NMR STUDIES OF BETA-THIOXO-KETONES . ROTATION AROUND C-C BOND AND ENERGY OF INTRAMOLECULAR HYDROGEN BOND O-H-S

The NMR spectra of several β-thioxoketones and their dependence on the temperature have been studied in various solvents (CS2, Tetrahydrofuran, Acrylnitrile). The spectra of compounds examined indicate that they exist almost entirely as OH⋯S H-bonded enol forms. In addition to the OH-rotation, CC bond the rotation has been observed. Thermodynamic results on intramolecular OHS H-bonding have been obtained from chemical shifts of the OH group. The influence of the solvent is discussed. © 1969.