N. A. Mukmeneva

Three-dimensional structure of phosphorus-containing heterocycles

ConclusionsBy means of dynamic PMR spectrometry, UV spectra, dipole moments, and ab-initio SCF MO LCAO calculations of model compounds, it has been shown that for 2-hydro-2-oxo-4,5,7,8-dibenzo-4H-1,3,2-dioxaphosphocins there is characteristically a three-component equilibrium with the participation of both of the boat-chair forms and one boat form with equatorial position of the P-H bond. The thermodynamic characteristics of the equilibrium have been determined.

Phenoxyl free radicals with a mercaptobenzothiazole fragment: Study of intramolecular motions by the EPR and ENDOR methods

Conclusions1.From the temperature dependence of the EPR spectrum for the free radical N-(4-hydroxy-3,5-di-tert-butylbenzyl)benzothiazole-2-thione, we determine the activation energy Ea=19.1 ±2.0 kcal/mole for hindered rotation about the Cα-Cβ bond. We estimate the rotational correlation time and the conformational angles.2.For the isomeric free radical S-(4-hydroxy-3,5-di-tert-butylbenzyl (-2-mercaptobenzothiazole, rotation about the Cα-Cβ bond is practically free (Ea=3.5 ± 1.0 kcal/mole), which is explained by the smaller steric effect of the substituents.