Chirality dependent inverse-melting and re-entrant gelation in α-cyclodextrin/1-phenylethylamine mixtures
Reut Shapira1, Sapir Katalan1, Rachel Edrei1
1Schulich Faculty of Chemistry, Technion - Israel Institute of Technology Technion City 3200008 Haifa Israel yoav@ch.technion.ac.il.
Abstract:
Solutions of cyclohexakis-(1→4)-α-d-glucopyranosyl, α-cyclodextrin, αCD, in R-(+)-1-phenylethylamine, αCD/R-PEA, and S-(-)-1-phenylethylamine, αCD/S-PEA, display abnormal phase transitions that strongly depend on supramolecular diastereomeric interactions. While αCD/R-PEA mixtures show one sol-gel inverse-melting phase transition, αCD/S-PEA mixtures show temperature dependent gel-sol-gel re-entrant behavior. NMR, Raman spectroscopy, microscopy and X-ray scattering measurements reveal that hydrogen bond weakening in solution, as well as changes in crystal composition are responsible for entropy increase and gel formation upon heating.
More Related Videos
Related Concept Videos
Racemic Mixtures and the Resolution of Enantiomers
Stereoisomerism of Cyclic Compounds
Disubstituted Cyclohexanes: cis-trans Isomerism
In cyclohexane, the substituents can occupy different positions generating distinct isomers....
Prochirality
Properties of Enantiomers and Optical Activity
Stability of Substituted Cyclohexanes
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...


