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シラピラー[n]アーネス: 強化された電子結合と構成の多用途性

  • 0Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.

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Hybridization of Atomic Orbitals II 03:35

32.3K

sp3d and sp3d 2 Hybridization

To describe the five bonding orbitals in a trigonal bipyramidal arrangement, we must use five of the valence shell atomic orbitals (the s orbital, the three p orbitals, and one of the d orbitals), which gives five sp3d hybrid orbitals. With an octahedral arrangement of six hybrid orbitals, we must use six valence shell atomic orbitals (the s orbital, the three p orbitals, and two of the d orbitals in its valence shell), which gives six sp3d 2 hybrid...

Stability of Conjugated Dienes 01:28

3.4K

Introduction
A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.

The two main factors contributing to the enhanced stability of conjugated systems are the delocalization of π electrons and the sp2 hybridization of the carbons forming the single bonds.
Planar Conformers of Conjugated Dienes
Conjugated dienes adopt two planar configurations, s-cis and...

Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry 01:29

4.6K

Diels–Alder reactions between cyclic dienes locked in an s-cis configuration and dienophiles yield bridged bicyclic products.

Dienophiles with one or more electron-withdrawing substituents form stereochemically different products in which the substituents are oriented in an endo (towards) or exo (away) configuration relative to the double bond.

The endo isomer is formed faster and is the kinetic product. The exo isomer is more stable and is the thermodynamic...

Chirality at Nitrogen, Phosphorus, and Sulfur 02:30

5.7K

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...

[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction 01:16

10.2K

The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.

From a molecular orbital perspective, the interacting lobes of the two π systems must be in phase...

Diels–Alder Reaction Forming Cyclic Products: Stereochemistry 01:28

3.9K

The Diels–Alder reaction is one of the robust methods for synthesizing unsaturated six-membered rings. The reaction involves a concerted cyclic movement of six π electrons: four π electrons from the diene and two π electrons from the dienophile.

For the electrons to flow seamlessly between the two π systems, specific stereochemical and conformational requirements must be met.
Stereochemical Orbital Symmetry
The frontier molecular orbitals that satisfy the symmetry...