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¹H NMR: Complex Splitting

¹H NMR: Complex Splitting

A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied...

¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR

¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR

The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.

¹H NMR of Conformationally Flexible Molecules: Temporal Resolution

¹H NMR of Conformationally Flexible Molecules: Temporal Resolution

At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...

Electrophilic 1,2- and 1,4-Addition of HX to 1,3-Butadiene

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The electrophilic addition of hydrogen halides such as HBr to alkenes and nonconjugated dienes gives a single product as per Markovnikov’s rule.

Carbon Skeletons

Carbon Skeletons

Life on Earth is carbon-based, as all macromolecules that make up living organisms contain carbon atoms. All organic compounds have a carbon backbone. Each carbon atom is tetravalent and can bond with four other atoms, making it an extraordinarily flexible component of biological molecules. Because carbon’s valence electrons are stable, it rarely becomes an ion. As the carbon chain increases in length, structural modifications such as ring structures, double bonds, and branching side...

¹H NMR: Long-Range Coupling

¹H NMR: Long-Range Coupling

The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene...

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Related Experiment Video

Updated: Apr 11, 2026

High-Sensitivity Nuclear Magnetic Resonance at Giga-Pascal Pressures: A New Tool for Probing Electronic and Chemical Properties of Condensed Matter under Extreme Conditions

High-Sensitivity Nuclear Magnetic Resonance at Giga-Pascal Pressures: A New Tool for Probing Electronic and Chemical Properties of Condensed Matter under Extreme Conditions

Published on: October 10, 2014

Backbone NxH compounds at high pressures.

Alexander F Goncharov¹, Nicholas Holtgrewe², Guangrui Qian³

¹Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, 350 Shushanghu Road, Hefei, Anhui 230031, China.

The Journal of Chemical Physics

|June 8, 2015

Summary

This summary is machine-generated.

Researchers explored nitrogen-hydrogen (N-H) compounds under high pressure. They discovered new oligomeric materials formed via barochemistry and photochemistry, potentially useful as energy-dense materials or planetary ices.

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High-Sensitivity Nuclear Magnetic Resonance at Giga-Pascal Pressures: A New Tool for Probing Electronic and Chemical Properties of Condensed Matter under Extreme Conditions

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$Synthesis and Microdiffraction at Extreme Pressures and Temperatures$

Synthesis and Microdiffraction at Extreme Pressures and Temperatures

Published on: October 7, 2013

Area of Science:

Materials Science
High-Pressure Physics
Computational Chemistry

Background:

Nitrogen (N2) and hydrogen (H2) mixtures are studied under extreme conditions.
Previous research identified complex van der Waals compounds in N-H systems.

Purpose of the Study:

Investigate the structural and chemical transformations of N2-H2 mixtures under high pressure.
Explore novel synthesis pathways for high energy-density materials.

Main Methods:

Combined optical and synchrotron X-ray diffraction using diamond anvil cells.
Employed first-principles theoretical structure predictions.
Investigated barochemistry (pressure-induced) and photochemistry (light-induced) transformations.

Main Results:

Observed formation of complex van der Waals N-H compounds above 10 GPa.
Discovered abrupt transformation to new oligomeric materials via barochemistry (>47 GPa) and photochemistry (≥10 GPa).
Oligomeric compounds are recoverable to ambient pressure at low temperatures (<130 K) and metastable at room temperature down to 3.5 GPa.

Conclusions:

Oligomeric N-H materials are thermodynamically favored over N2, H2, and NH3 mixtures above ~40 GPa.
Identified new synthesis routes for environmentally benign, high energy-density materials.
These materials may exist as alternative planetary ices under extraterrestrial conditions.