Chemical Exchange

Bain, Alex D.

doi:10.1016/s0066-4103(07)63002-6

Cited by 35 publications

(20 citation statements)

References 173 publications

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“…The EXSY pulse sequence ( Figure 14 ) is comprised of three 90° pulses ( Table S1 ). The first pulse frequency labels all spins in the system, which are then allowed to evolve over a variable delay period t 1 [ 107 ]. The second pulse inverts all spins which relax and possibly undergo chemical exchange during the mixing time t m and are observed following the application of a third pulse [ 107 ].…”

Section: Solid State Nmr Spectroscopy Techniquesmentioning

confidence: 99%

“…The first pulse frequency labels all spins in the system, which are then allowed to evolve over a variable delay period t 1 [ 107 ]. The second pulse inverts all spins which relax and possibly undergo chemical exchange during the mixing time t m and are observed following the application of a third pulse [ 107 ]. All spins maintain the labeling that was created by the first pulse which causes signals related to chemical exchange between sites to appear as off-diagonal cross peaks.…”

Section: Solid State Nmr Spectroscopy Techniquesmentioning

confidence: 99%

“…All spins maintain the labeling that was created by the first pulse which causes signals related to chemical exchange between sites to appear as off-diagonal cross peaks. Off-diagonal peaks have different coordinates on each frequency axis in the two-dimensional spectrum, whereas diagonal peaks (same coordinates on each axis) represent the fraction of spin which did not undergo chemical exchange ( Figure 15 ) [ 107 ]. Multiple exchange processes are represented by multiple sets of cross peaks.…”

Section: Solid State Nmr Spectroscopy Techniquesmentioning

confidence: 99%

See 2 more Smart Citations

Use of Solid-State NMR Spectroscopy for the Characterization of Molecular Structure and Dynamics in Solid Polymer and Hybrid Electrolytes

et al. 2021

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Solid-state NMR spectroscopy is an established experimental technique which is used for the characterization of structural and dynamic properties of materials in their native state. Many types of solid-state NMR experiments have been used to characterize both lithium-based and sodium-based solid polymer and polymer–ceramic hybrid electrolyte materials. This review describes several solid-state NMR experiments that are commonly employed in the analysis of these systems: pulse field gradient NMR, electrophoretic NMR, variable temperature T1 relaxation, T2 relaxation and linewidth analysis, exchange spectroscopy, cross polarization, Rotational Echo Double Resonance, and isotope enrichment. In this review, each technique is introduced with a short description of the pulse sequence, and examples of experiments that have been performed in real solid-state polymer and/or hybrid electrolyte systems are provided. The results and conclusions of these experiments are discussed to inform readers of the strengths and weaknesses of each technique when applied to polymer and hybrid electrolyte systems. It is anticipated that this review may be used to aid in the selection of solid-state NMR experiments for the analysis of these systems.

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Section: Solid State Nmr Spectroscopy Techniquesmentioning

confidence: 99%

Section: Solid State Nmr Spectroscopy Techniquesmentioning

confidence: 99%

Section: Solid State Nmr Spectroscopy Techniquesmentioning

confidence: 99%

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Use of Solid-State NMR Spectroscopy for the Characterization of Molecular Structure and Dynamics in Solid Polymer and Hybrid Electrolytes

et al. 2021

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“…The un-inverted peaks in the case of the cosine-sine modulated experiment, viz. the acid and the water peak show the characteristic dip 49,50 in their intensity profiles whereas the protonated acetone peak exhibits the typical inversion recovery behaviour.…”

Section: Resultsmentioning

confidence: 99%

Study of multi-site chemical exchange in solution state by NMR: 1D experiments with multiply selective excitation

Pal

2010

J Chem Sci

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Chemical exchange in solution state has been investigated traditionally by both 1D and 2D NMR, permitting the extraction of kinetic parameters (e.g. the spin-lattice relaxation time T 1 , the exchange rate constant k and the activation parameters). This work demonstrates a simple 1D NMR approach employing multiply selective excitation to study multi-site exchange processes in solution, applying it to systems that exhibit three-site exchange. This approach involves simultaneous excitation of all -or a chosen subset of -the exchanging sites by using an appropriately modulated shaped radiofrequency pulse. The pulse sequence, as well as analysis is summarized. Significant features of the experiment, which relies on sign labelling of the exchanging sites, include considerably shorter experiment time compared to standard 2D exchange work, clear definition of the exchange time window and uniform pulse non-ideality effects for all the exchanging sites. Complete kinetic information is reported in the study of dynamic processes in superacid solutions of two weak bases, studied by 1 H NMR. An analytical solution, leading to the determination of four rate parameters, is presented for proton exchange studies on these systems, which involve a mixture of two weak bases in arbitrary concentration ratio, and stoichiometric excess of the superacid.

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“…Chemical exchange studies provide provides fundamental knowledge on the physical chemistry of the molecules and it is an area continuing interest to the research community (2,20–23). For example in a recent study Bain and co-works (24) add valuable information of the effect of solvent on the dynamics of push-pull ethylene (25).…”

Section: Discussionmentioning

confidence: 99%

Modulations in restricted amide rotation by steric induced conformational trapping

Krishnan

Thompson

Goto

et al. 2012

Chemical Physics Letters

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The rotation around the amide bond in N,N-diethyl-m-toluamide (m-DEET) has been studied extensively and often used in laboratory instructions to demonstrate the phenomenon of chemical exchange. Herein, we show that a simple modification to N,N-diethyl-o-toluamide (o-DEET) significantly alters the dynamics of the restricted rotation around the amide bond due to steric interactions between the ring methyl group and the two N-ethyl groups. This alters the classic two-site exchange due to restricted rotation around the amide bond, to a three-site exchange, with the third conformation trapped at a higher-energy state compared to the other two. This often overlooked phenomenon is elucidated using variable-temperature NMR, two-dimensional exchange spectroscopy and molecular modeling studies.

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Chemical Exchange

Cited by 35 publications

References 173 publications

Use of Solid-State NMR Spectroscopy for the Characterization of Molecular Structure and Dynamics in Solid Polymer and Hybrid Electrolytes

Use of Solid-State NMR Spectroscopy for the Characterization of Molecular Structure and Dynamics in Solid Polymer and Hybrid Electrolytes

Study of multi-site chemical exchange in solution state by NMR: 1D experiments with multiply selective excitation

Modulations in restricted amide rotation by steric induced conformational trapping

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