Video Experimental Relacionado

Updated: Aug 9, 2026

Generation of Local CA1 γ Oscillations by Tetanic Stimulation

Generation of Local CA1 γ Oscillations by Tetanic Stimulation

Published on: August 14, 2015

Las constantes de acoplamiento de espín-espín Geminal 2JCCH como sondas del ángulo de torsión fi glicosídica en

Thomas E Klepach¹, Ian Carmichael, Anthony S Serianni

¹Department of Chemistry and Biochemistry, University of Notre Dame, Indiana 46556-5670, USA.

Journal of the American Chemical Society

|July 7, 2005

Resumen

Los acoplamientos de RMN carbono-hidrógeno de dos enlaces ((2) J ((CCH)) en los anillos de aldopyranosilo están influenciados por las torsiones C-O. Nuevas ecuaciones interpretan estos acoplamientos, ayudando al análisis de la estructura de RMN de los oligosacáridos.

Área de la Ciencia:

Química computacional es la química computacional.
Espectroscopia de resonancia magnética nuclear Espectroscopia de resonancia magnética nuclear Espectroscopia de resonancia magnética nuclear Espectroscopia de resonancia magnética nuclear
Química de los carbohidratos Química de los carbohidratos

Sus antecedentes:

Las constantes de acoplamiento de espín-espín de la RMN de dos enlaces (13)C-(1)H ((2)J(CCH)) son sensibles a la estereoquímica en los anillos de aldopiranosilo.
Estudios previos indican dependencia de la orientación del sustituto y las torsiones C-O.

Objetivo del estudio:

Para aclarar teóricamente la dependencia de (2) J ((C2, H1) y (2) J ((C1, H2) en los ángulos de torsión C-O (phi y alfa) en los anillos de aldopyranosilo.
Desarrollar nuevas ecuaciones parametrizadas para interpretar estos acoplamientos de RMN.
Evaluar la utilidad de (2) J (((C2, H1) como una restricción estructural de RMN para los enlaces glucósidos.

Principales métodos:

Los cálculos de la teoría funcional de la densidad (DFT) se realizaron en modelos de anillos de piranosilo.
Los cálculos exploraron cuatro configuraciones relativas en C1 y C2, incluido un derivado de 2-deoxy.
Los acoplamientos J computarizados fueron validados contra mediciones experimentales.

Principales resultados:

(2) J ((CCH) muestra una dependencia primaria de la torsión C-O del carbono que lleva el protón acoplado y una dependencia secundaria de la torsión C-O del carbono acoplado.
Los efectos del par solitario de oxígeno en las longitudes de enlace influyen significativamente en la vía de acoplamiento.
Se obtuvieron nuevas ecuaciones parametrizadas para (2) J (((C1,H2) y (2) J ((C2,H1).

Conclusiones:

Las ecuaciones derivadas proporcionan un marco para interpretar (2) J ((CCH) en los sistemas de aldopyranosilo.
La ecuación para (2) J (((C2, H1) es particularmente valiosa para determinar el ángulo de torsión C1-O1 (phi) en los oligosacáridos.
Este trabajo mejora la aplicación de la espectroscopia de RMN en la aclaración de la estructura de los carbohidratos.

Más Videos Relacionados

Scalable Quantum Integrated Circuits on Superconducting Two-Dimensional Electron Gas Platform

Scalable Quantum Integrated Circuits on Superconducting Two-Dimensional Electron Gas Platform

Published on: August 2, 2019

Recording Gap Junction Current from Xenopus Oocytes

Recording Gap Junction Current from Xenopus Oocytes

Published on: January 21, 2022

Videos de Conceptos Relacionados

Spin–Spin Coupling Constant: Overview

Spin–Spin Coupling Constant: Overview

In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...

Spin–Spin Coupling: One-Bond Coupling

Spin–Spin Coupling: One-Bond Coupling

Coupling interactions are strongest between NMR-active nuclei bonded to each other, where spin information can be transmitted directly through the pair of bonding electrons. While nuclei polarize their electrons to the opposite spins, the bonding electron pair has opposite spins. Configurations with antiparallel nuclear spins are expected to be lower in energy. When coupling makes antiparallel states more favorable, J is considered to have a positive value. The one-bond coupling constant, 1J,...

Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)

Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)

Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...

Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)

Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)

Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the involved orbitals. The...

Problem-Solving: Tuning of a Guitar String

Problem-Solving: Tuning of a Guitar String

In the case of stringed instruments like the guitar, the elastic property that determines the speed of the sound produced is its linear mass density or the mass per unit length. This is simply called the linear density. If the string's linear density is constant along the string, then the linear density is simply the total mass divided by the total length.
The string's wave speed can be regulated by varying the linear density. Tension is the other property that determines the speed of...

The Swing Equation

The Swing Equation

The Swing Equation is a fundamental tool in power system dynamics, especially for analyzing the behavior of generating units like three-phase synchronous generators. This equation emerges from applying Newton's second law to the rotor of a generator, encompassing factors such as inertia, angular acceleration, and the interplay between mechanical and electrical torques.
In a steady-state operation, the mechanical torque (Τm) supplied to the generator is balanced by the electrical torque (Τe)...