Related Experiment Video
Updated: Jun 19, 2026
A Strategy for Sensitive, Large Scale Quantitative Metabolomics
Published on: May 27, 2014
Pseudopolymorphism in tetradeca-2,6-O-methyl-beta-cyclodextrin: the crystal structures for two new
J J Stezowski1, W Parker, S Hilgenkamp
1Contribution from the Department of Chemistry, Center for Materials Research and Analysis, University of Nebraska, Lincoln, Nebraska 68588-0304, USA.
Abstract:
Tetradeca-2,6-O-methyl-beta-cyclodextrin, per-2,6-OMe-beta-CD, is an unusual beta-cyclodextrin, beta-CD, derivative because it has a negative thermal solubility coefficient in aqueous solution. This report describes two new crystal structures for hydrates of per-2,6-OMe-beta-CD crystallized at different temperatures: per-2,6-OMe-beta-CD.1.08H(2)O crystallized at 50 degrees C and per-2,6-OMe-beta-CD.14.7H(2)O crystallized at 4 degrees C. The crystal structure for per-2,6-OMe-beta-CD.1.08H(2)O reveals conformational flexibility in the methylated beta-CD molecule; two adjacent glucose residues are disordered as a result of their adopting different tilts with respect to the O(4) plane characterizing the molecule. When one conformation is present there is a water molecule in the lattice (0.5 population parameter); said water is displaced by the methyl of a methoxy substituent when the other conformer is present.
Related Concept Videos
02:34Structural Isomerism
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...
02:52Stereoisomerism
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
02:43Isomerism
02:01Isomerism in Alkenes
An isomer is called cis-2-butene when the methyl groups are on the same side of the double bond, and the other stereoisomer, in which methyl groups are on the opposite side of the double bond, is called trans-2-butene. The cis and trans stereoisomers are not...
01:28Structures of Carboxylic Acid Derivatives
Carboxylic acid derivatives contain an acyl group attached to a heteroatom such as chlorine, oxygen, or nitrogen. The carbonyl carbon and oxygen are both sp2-hybridized with an unhybridized p orbital.
The three sp2 orbitals of the carbonyl carbon form three σ bonds, one each with the carbonyl oxygen, the α carbon, and the heteroatom, whereas the other two sp2 orbitals of the carbonyl oxygen are occupied by the lone pairs. Further, the unhybridized p...
01:29Imperfections in Crystal Structure: Non-Stoichiometric Defects