Related Experiment Video
Updated: May 25, 2026
09:26
Cellular Lipid Extraction for Targeted Stable Isotope Dilution Liquid Chromatography-Mass Spectrometry Analysis
Published on: November 17, 2011
Two polymorphs of 20-desmethyl-beta-carotene
Madeleine Helliwell1, Synnøve Liaaen-Jensen, James Wilkinson
1Department of Chemistry, University of Manchester, Manchester M13 9PL, England. madeleine.helliwell@manchester.ac.uk
Summary
Two crystal forms of 20-desmethyl-beta-carotene were identified, revealing distinct molecular structures and packing arrangements. This research provides insights into how structural changes affect carotene properties.
Area of Science:
- Crystallography
- Carotenoid chemistry
- Structural analysis
Background:
- Beta-carotene is a vital nutrient and a common carotenoid.
- Understanding the structural variations of carotenoids is crucial for their biological functions.
Purpose of the Study:
- To investigate the crystal structures of two polymorphs of 20-desmethyl-beta-carotene.
- To compare the structural differences between the monoclinic and triclinic polymorphs.
- To elucidate the impact of the methyl group's absence on the carotene structure.
Main Methods:
- Recrystallization of 20-desmethyl-beta-carotene from pyridine and water.
- X-ray diffraction to determine the crystal structures of the two polymorphs.
- Analysis of molecular conformation, polyene chain planarity, and crystal packing.
Main Results:
- Two polymorphs (monoclinic and triclinic) of 20-desmethyl-beta-carotene were successfully synthesized and characterized.
- Significant differences were observed in the degree of polyene chain nonplanarity and end-ring twist angles between the polymorphs.
- Distinct crystal packing arrangements were identified, including intermolecular contacts and pi-pi stacking interactions.
Conclusions:
- The absence of the methyl group in 20-desmethyl-beta-carotene leads to unique structural conformations and packing compared to beta-carotene.
- Structural variations in polymorphs influence molecular properties and potentially biological activity.
- This study enhances understanding of structure-property relationships in carotenoids.
Related Concept Videos
02:52Stereoisomerism
Isomerism in Complexes
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...
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...
02:37Disubstituted Cyclohexanes: cis-trans Isomerism
Depending upon the different spatial orientation of the substituents, the disubstituted cycloalkanes exhibit two types of stereoisomers. The cis isomers have the substituents on the same side of the ring, whereas the trans isomers have the substituents on the opposite sides. These stereoisomers exhibit different physical properties and cannot be interconverted without breaking the carbon-carbon bonds.
In cyclohexane, the substituents can occupy different positions generating distinct isomers.
In cyclohexane, the substituents can occupy different positions generating distinct isomers.
02:43Isomerism
Isomers are molecules with the same molecular formula but different structural arrangements. Isomers can be further classified into constitutional isomers and stereoisomers. Constitutional isomers differ in the connectivity of their constituent atoms. For example, 2-butanol and diethyl ether are constitutional isomers, as they have the same chemical formula, C4H10O, but differ in the connectivity of the carbon and oxygen atoms. Constitutional isomers have different physical and chemical...
02:32Stereoisomers
On the basis of mirror symmetry, stereoisomers of an organic molecule can be further classified into diastereomers and enantiomers. Diastereomers are stereoisomers that are not mirror images of each other. Substituted alkenes, such as the cis and trans isomers of 2-butene, are diastereomers, as these molecules exhibit different spatial orientations of their constituent atoms, are not mirror images of each other, and do not interconvert. Here, the interconversion is suppressed due to restricted...
02:33Stereoisomerism of Cyclic Compounds
In this lesson, we delve into the role of ring conformation and its stability, which determines the spatial arrangement and, consequently, the molecular symmetry and stereoisomerism of cyclic compounds. 1,2-Dimethylcyclohexane is used as a case study to evaluate the possible number of stereoisomers. Here, given the multiple (n = 2) chiral centers, there are 2n = 4 possible configurations that lack a plane of symmetry, as the ring skeleton exists in a non-planar chair conformation. In addition,...
01:27Pharmaceutical Alternatives: Polymorphic Form-Related and Particle Size-Related Therapeutic Nonequivalence
Changes in polymorphic forms can significantly influence the bioavailability of poorly soluble drugs. Although the FDA defines pharmaceutical equivalence based on having the same active ingredient, dosage form, and route of administration, it does not automatically disqualify products with different polymorphic forms. This means two products with different polymorphs can still be deemed pharmaceutically equivalent. However, polymorphic differences can affect properties like wettability,...