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Related Concept Videos

Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)01:22

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

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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...
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Spin–Spin Coupling Constant: Overview01:08

Spin–Spin Coupling Constant: Overview

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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...
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Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)01:20

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

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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...
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Spin–Spin Coupling: One-Bond Coupling01:17

Spin–Spin Coupling: One-Bond Coupling

1.2K
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,...
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Coupled Reactions01:17

Coupled Reactions

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Cellular processes such as building and breaking down complex molecules occur through stepwise chemical reactions. Some of these chemical reactions are spontaneous and release energy, whereas others require energy to proceed. Cells often couple the energy-releasing reaction with the energy-requiring one to carry out important cell functions. 
Energy in adenosine triphosphate or ATP molecules is easily accessible to do work. ATP powers the majority of energy-requiring cellular reactions....
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Simplification of a Force and Couple System: II01:23

Simplification of a Force and Couple System: II

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In a three-dimensional system, multiple forces can act on an object. These forces can be combined into a single equivalent force, known as the resultant force. Similarly, the moments generated by these forces can be combined into a single equivalent moment, the resultant couple moment. In certain situations, these two entities may not be mutually perpendicular, meaning they do not have a 90-degree angle between them. This unique condition requires a deeper understanding of the interplay between...
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Related Experiment Video

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Author Spotlight: Universal Molecular Retention with 11-Fold Expansion Microscopy
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Universal J-coupling prediction.

Juuso Lehtivarjo1, Matthias Niemitz, Samuli-Petrus Korhonen

  • 1School of Pharmacy, University of Eastern Finland , P.O. Box 1627, 70211 Kuopio, Finland.

Journal of Chemical Information and Modeling
|March 6, 2014
PubMed
Summary

This study introduces a fast, data-driven method for predicting small molecule J-coupling constants. The approach enhances automatic spectrum analysis by combining database searching with k-Nearest Neighbors regression for accurate predictions.

Area of Science:

  • Computational Chemistry
  • Spectroscopy
  • Data Science

Background:

  • Accurate prediction of J-coupling constants is crucial for small molecule characterization in chemical analysis.
  • Existing methods may lack the speed and coverage required for automated spectral analysis.

Purpose of the Study:

  • To develop a data-driven computational method for predicting small molecule J-coupling constants.
  • To optimize the method for speed, maintainability, and prediction coverage within automated spectral analysis workflows.

Main Methods:

  • Database searching using hash codes derived from coupling path atom types.
  • k-Nearest Neighbors (kNN) regression utilizing atomic charges, torsion angles, and steric bulk.
  • Parametrization of substituent and conformational dependencies.

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Main Results:

  • The developed method demonstrates efficient retrieval of J-coupling data through hash-based database searching.
  • kNN regression effectively resolves substituent and conformational effects on coupling constants.
  • The approach is designed for high performance in automated spectral analysis.

Conclusions:

  • The presented data-driven approach offers a fast and maintainable solution for J-coupling prediction.
  • This method can significantly improve the efficiency and accuracy of automated small molecule spectrum analysis.
  • The integration of hash codes and kNN regression provides a robust framework for computational chemistry applications.