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Related Concept Videos

Stereoisomerism02:52

Stereoisomerism

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...
Prochirality02:05

Prochirality

The concept of prochirality leads to the nomenclature of the individual faces of a molecule and plays a crucial role in the enantioselective reaction. It is a concept where two or more achiral molecules react to produce chiral products. A typical process is the reaction of an achiral ketone to generate a chiral alcohol. Here, the achiral reactant reacts with an achiral reducing agent, sodium borohydride, to generate an equimolar mixture of the chiral enantiomers of the product. For example, an...
Electrophilic Aromatic Substitution: Chlorination and Bromination of Benzene01:15

Electrophilic Aromatic Substitution: Chlorination and Bromination of Benzene

Chlorination and bromination are important classes of electrophilic aromatic substitutions, where benzene reacts with chlorine or bromine in the presence of a Lewis acid catalyst to give halogenated substitution products. A Lewis acid such as aluminium chloride or ferric chloride catalyzes the chlorination, and ferric bromide catalyzes the bromination reactions. During the bromination of alkenes, bromine polarizes and becomes electrophilic. However, in the bromination of benzene, the bromine...
Chirality at Nitrogen, Phosphorus, and Sulfur02:30

Chirality at Nitrogen, Phosphorus, and Sulfur

Chirality is most prevalent in carbon-based tetrahedral compounds, but this important facet of molecular symmetry extends to sp3-hybridized nitrogen, phosphorus and sulfur centers, including trivalent molecules with lone pairs. Here, the lone pair behaves as a functional group in addition to the other three substituents to form an analogous tetrahedral center that can be chiral.
A consequence of chirality is the need for enantiomeric resolution. While this is theoretically possible for all...
Predicting Molecular Geometry02:27

Predicting Molecular Geometry

VSEPR Theory for Determination of Electron Pair Geometries
¹H NMR Chemical Shift Equivalence: Enantiotopic and Diastereotopic Protons00:58

¹H NMR Chemical Shift Equivalence: Enantiotopic and Diastereotopic Protons

Replacing each alpha-hydrogen in chloroethane by bromine (or a different functional group) yields a pair of enantiomers. Such protons are called prochiral or enantiotopic and are related by a mirror plane. Enantiotopic protons are chemically equivalent in an achiral environment. Because most proton NMR spectra are recorded using achiral solvents, enantiotopic hydrogens yield a single signal.
In chiral compounds such as 2-butanol, replacing the methylene hydrogens at C3 produces a pair of...

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Combining Solid-state and Solution-based Techniques: Synthesis and Reactivity of Chalcogenidoplumbates(II or IV)
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Published on: December 29, 2016

Two polymorphs of 2-(4-chlorophenyl)-4-methylchromenium perchlorate.

Alexander D Roshal1, Artur Sikorski, Vyacheslav N Baumer

  • 1Institute of Chemistry, V. N. Karazin Kharkiv National University, Svoboda Square 4, 60177 Kharkiv, Ukraine.

Acta Crystallographica. Section C, Crystal Structure Communications
|November 9, 2007
PubMed
Summary

Two polymorphs of 2-(4-chlorophenyl)-4-methylchromenium perchlorate were identified. Differences in their crystal structures, including ion pairing and intermolecular interactions, likely explain their distinct colors.

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Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of Phosphorus(I)
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Published on: November 22, 2016

Area of Science:

  • Crystallography
  • Solid-state chemistry
  • Materials science

Background:

  • Polymorphism, the ability of a solid material to exist in more than one crystal form, is crucial in determining material properties.
  • Chromenium salts are known for their diverse applications, necessitating a thorough understanding of their solid-state structures.

Purpose of the Study:

  • To investigate the crystal structures of two monoclinic polymorphs of 2-(4-chlorophenyl)-4-methylchromenium perchlorate.
  • To elucidate the intermolecular interactions and packing arrangements responsible for the observed polymorphism and color differences.

Main Methods:

  • Single-crystal X-ray diffraction was employed to determine the crystal structures of the two polymorphs.
  • Analysis of crystallographic data included space group determination, unit cell parameters, and detailed examination of intermolecular interactions (e.g., pi-pi stacking, hydrogen bonding).

Main Results:

  • Two monoclinic polymorphs, designated (Ia) and (Ib) with space groups P2(1)/n and P2(1)/c respectively, were obtained.
  • Both polymorphs feature ion pairs formed by cations and anions, stabilized by Cl-O...pi interactions.
  • Distinct packing arrangements and intermolecular interactions, including pi-pi stacking and C-H...O hydrogen bonds, were observed in each polymorph, leading to differences in aromatic skeleton orientation and ultimately, color.

Conclusions:

  • The study successfully characterized two novel polymorphs of 2-(4-chlorophenyl)-4-methylchromenium perchlorate.
  • The observed differences in crystal structure and intermolecular interactions are directly correlated with the distinct colors of the polymorphs.
  • This research provides valuable insights into the structure-property relationships of chromenium salts and the phenomenon of polymorphism.