Conformational analysis. Part 11. A theoretical and nuclear magnetic resonance lanthanide-induced shift (LIS) study of the conformation of α-tetralone

Abstract

The conformational behaviour in solution of α-tetralone [3,4-dihydronaphthalen-1 (2H)-one] has been studied through a combination of theoretical methods and LIS analysis. The force-field method MMPI predicts the envelope conformation as more stable (ca. 0.94 kcal mol^–1), in accordance with previous results, whilst the semi-empirical MNDO method gives equal energies for the envelope and half-chair conformations due possibly to the under-evaluation of the π-conjugation energy. The LIS analysis cannot differentiate between the two possible conformations because, in both cases, well defined minima with good agreement factors (%Rx: ca. 1.4 and 1.6) are obtained. The complexation geometry found for the lanthanide ion in α-tetralone has been used to analyse the cyclohex-2-en-1-one LIS in order to resolve the under-determination for this system found in the previous LIS analysis, giving in this way better defined minima in the correlation coefficients.