Low temperature enantiotropic nematic phases from V-shaped, shape-persistent molecules

• Matthias Lehmann and
• Jens Seltmann

Beilstein J. Org. Chem. 2009, 5, No. 73, doi:10.3762/bjoc.5.73

• length on the phase transition temperatures. Only with the heptyl chains do the transition temperatures decrease significantly. A closer look at transition enthalpies and entropies reveal very small values for 3a and 3b (ΔH = 0.1 kJ·mol−1; ΔS = 0.2 J·K−1·mol−1). Entropy values approaching zero, i.e

The vicinal difluoro motif: The synthesis and conformation of erythro- and threo- diastereoisomers of 1,2-difluorodiphenylethanes, 2,3-difluorosuccinic acids and their derivatives

• David O'Hagan,
• Henry S. Rzepa,
• Martin Schüler and
• Alexandra M. Z. Slawin

Beilstein J. Org. Chem. 2006, 2, No. 19, doi:10.1186/1860-5397-2-19

• geometries were optimized at this level for a gas phase model, and corrected for entropy and zero-point energy differences at this level. A separate solvation correction (chloroform) was applied using a continuum model (PCPM) and the larger cc-pV5Z basis set (using pVTZ geometries). Chloroform was studied in

• originating predominantly from entropy and zero-point energy corrections (1.06 kcal/mol). This is also the conformer that most closely represents the X-ray structure (Figure 1). The solvent correction (which takes into account free energy differences associated with the solvent cavity, but does not allow for

• isomer has three distinct staggered conformations; c, d and e. Computationally, this requires modelling the subtle balance between the correlation effects due to gauche fluorine atoms and those due to gauche phenyl rings. In the gas phase (entropy and zero energy corrected) conformers c and d are iso