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Related Concept Videos

Disubstituted Cyclohexanes: cis-trans Isomerism02:37

Disubstituted 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.
Stereoisomerism of Cyclic Compounds02:33

Stereoisomerism 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,...
Cycloalkanes02:28

Cycloalkanes

Cycloalkanes are saturated cyclic hydrocarbons with carbon atoms arranged in the form of rings. They have two fewer hydrogen atoms than the corresponding acyclic alkane; therefore, their general formula is CnH2n. The structural formulas of cycloalkanes are simplified using the line-angle representation. The regular polygons are used to represent the cycloalkane rings, with each side representing a carbon-carbon bond.
The IUPAC nomenclature of cycloalkanes follows similar rules that apply to...
Stability of Substituted Cyclohexanes02:30

Stability of Substituted Cyclohexanes

This lesson discusses the stability of substituted cyclohexanes with a focus on energies of various conformers and the effect of 1,3-diaxial interactions.
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...
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Related Experiment Video

Updated: Jun 23, 2026

Preparation of Enantiopure Non-Activated Aziridines and Synthesis of Biemamide B, D, and epiallo-Isomuscarine
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Preparation of Enantiopure Non-Activated Aziridines and Synthesis of Biemamide B, D, and epiallo-Isomuscarine

Published on: June 13, 2022

Two isomeric cucurbitane derivatives.

Maciej Kubicki1, Hanna Koenig, Zdzisław Paryzek

  • 1Department of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznań, Poland. mkubicki@amu.edu.pl

Acta Crystallographica. Section C, Crystal Structure Communications
|May 2, 2009
PubMed
Summary

This study details two isomeric cucurbitane derivatives, highlighting how differing double bond positions impact molecular conformation and substituent orientation. These findings offer insights into the structural variations within cucurbitane compounds.

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Area of Science:

  • Organic Chemistry
  • Structural Chemistry
  • Natural Product Chemistry

Background:

  • Cucurbitanes are a class of tetracyclic triterpenoids found in plants.
  • Isomeric variations in cucurbitanes can lead to significant differences in their three-dimensional structures.
  • Understanding these structural nuances is crucial for elucidating their biological activities.

Purpose of the Study:

  • To characterize and compare the crystal structures of two isomeric cucurbitane derivatives.
  • To investigate the impact of double bond position on molecular conformation and substituent orientation.
  • To provide detailed structural data for these specific cucurbitane compounds.

Main Methods:

  • Single-crystal X-ray diffraction was employed to determine the molecular structures.
  • Analysis of bond lengths, bond angles, and torsion angles to describe conformations.
  • Comparison of substituent orientations (axial vs. equatorial) in the two isomers.

Main Results:

  • Two isomeric cucurbitane derivatives, 3beta,7alpha,11beta-triacetoxycucurbit-5(10)-ene and 3beta,7alpha,11beta-triacetoxy-5alpha-cucurbit-1(10)-ene, were structurally elucidated.
  • Differences in the endocyclic double bond position resulted in distinct four-ring system conformations.
  • Variations in the orientation of acetoxy groups at the 3beta and 11beta positions were observed between the isomers.
  • Disorder in the aliphatic chain fragments was noted in both crystal structures.

Conclusions:

  • The precise location of the double bond significantly influences the overall molecular shape of cucurbitanes.
  • Stereochemical differences, such as axial vs. equatorial substituent placement, arise from conformational changes.
  • The study provides valuable crystallographic data for understanding cucurbitane structure-activity relationships.