Gabriel Cuevas

Stereoelectronic interpretation of the unusual perlin effects and 1H NMR chemical shifts in 1,3-oxathiane

Abstract Interpretation of “anomalous”, Perlin effects and 1H NMR chemical shifts in 1,3-oxathiane seems plausible by consideration of the relative importance of stereoelectronic interactions in this heterocycle.

Reverse Perlin effects for all CH bonds in 1,3-Dithiane.

The reverse Perlin effects observed for all CH 1J coupling constants in 1,3-dithiane, i.e., 1J(CHa x) > 1J(CHe q), seem to support the existence of a dominant σc - s→σ*c - h stereoelectronic interaction, which leads to a weakening of the equatorial CH bonds in this heterocycle.

Enthalpic and entropic contributions to the S-C-P(O) anomeric effect

The conformational bahavior of the 2-(diphenylphosphinoyl)-1,3-dithiane was studied in the 258–323 K temperature range. Plots of ln K versus 1/T are linear, permitting evaluation of the enthalpic and entropic contributions of the S-C-P-(O) anomeric effect. Comparison with the corresponding thermodynamic data in the cyclohexyl analogue allows estimation of the enthalpic anomeric effect in this system: ca. 3.4 kcal/mol.