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Related Concept Videos

Chemical Shift: Internal References and Solvent Effects01:17

Chemical Shift: Internal References and Solvent Effects

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In an NMR sample, precise measurement of the absolute absorption frequencies of nuclei is difficult. A standard internal reference compound is added, and the frequency difference between the reference signal and sample signals is measured.
The internal reference compound generally used in NMR spectroscopy is tetramethylsilane (TMS). TMS is preferred because it is chemically inert, soluble in NMR solvents, and easily removable. Also, the highly shielded methyl protons in TMS yield an intense...
1.0K
NMR Spectroscopy: Chemical Shift Overview01:15

NMR Spectroscopy: Chemical Shift Overview

2.6K
The position of the absorption signal of a sample is reported relative to the position of the signal of tetramethylsilane (TMS), which is added as an internal reference while recording spectra. The difference between the absorption frequencies of the sample and TMS (in Hz) is divided by the spectrometer operating frequency (in MHz) to obtain a dimensionless quantity called the chemical shift. It is reported on the δ (delta) scale and expressed in parts per million.
For instance, the proton...
2.6K
¹H NMR Chemical Shift Equivalence: Homotopic and Heterotopic Protons01:03

¹H NMR Chemical Shift Equivalence: Homotopic and Heterotopic Protons

3.7K
Protons in identical electronic environments within a molecule are chemically equivalent and have the same chemical shift. The replacement test is a useful tool to identify chemical equivalence and predict NMR spectra. A substituent replaces each of the protons being examined and the resulting molecules are compared. If the same molecule is obtained, the protons are equivalent or homotopic. Replacement of any hydrogens in ethane by chlorine yields chloroethane because all six protons are...
3.7K
Imaging Studies II: Positron Emission Tomography and Scintigraphy01:25

Imaging Studies II: Positron Emission Tomography and Scintigraphy

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Positron Emission Tomography (PET) is a medical imaging technique that provides crucial insights into the body's physiological functions at a molecular level. It is an indispensable resource for diagnosing, staging, and monitoring various illnesses, notably cancer, neurological disorders, and cardiovascular conditions.
Fundamental Principles of PET
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Other Nuclides: 31P, 19F, 15N NMR01:16

Other Nuclides: 31P, 19F, 15N NMR

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Many organic, inorganic, and biological molecules contain spin-half nuclei such as nitrogen-15, fluorine-19, and phosphorus-31. As a result, NMR studies of these nuclei have found extensive applications in chemical and biological research.
While fluorine-19 and phosphorous-31 have high natural abundances (100%) and positive gyromagnetic ratios, nitrogen-15 has a low natural abundance and a negative gyromagnetic ratio. However, nitrogen-15 is still preferred over nitrogen-14 (which has a...
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¹H NMR Chemical Shift Equivalence: Enantiotopic and Diastereotopic Protons00:58

¹H NMR Chemical Shift Equivalence: Enantiotopic and Diastereotopic Protons

2.8K
Replacing each alpha-hydrogen in chloroethane by bromine (or a different functional group) yields a pair of enantiomers. Such protons are called prochiral or enantiotopic and are related by a mirror plane. Enantiotopic protons are chemically equivalent in an achiral environment. Because most proton NMR spectra are recorded using achiral solvents, enantiotopic hydrogens yield a single signal.
In chiral compounds such as 2-butanol, replacing the methylene hydrogens at C3 produces a pair of...
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Updated: Nov 13, 2025

Investigations on the GaIII Complex of EOB-DTPA and Its 68Ga Radiolabeled Analogue
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Thallium chemical shift referencing.

Roy E Hoffman1

  • 1Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel.

Journal of Magnetic Resonance (San Diego, Calif. : 1997)
|March 12, 2021
PubMed
Summary
This summary is machine-generated.

Accurate referencing of thallium (Tl) chemical shifts is challenging due to their sensitivity. This study precisely measures TlNO3 shifts at infinite dilution, providing crucial data for reliable nuclear magnetic resonance (NMR) referencing.

Keywords:
205Tl230TlChemical shiftThallium nmr

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Area of Science:

  • Nuclear Magnetic Resonance (NMR) Spectroscopy
  • Inorganic Chemistry
  • Physical Chemistry

Background:

  • Thallium (Tl) chemical shifts are highly sensitive to environmental conditions, complicating accurate referencing.
  • Existing literature often references Tl shifts indirectly using proton (1H) standards and empirical factors.
  • Previous studies referenced Tl shifts to thallium nitrate (TlNO3) in aqueous solution at infinite dilution.

Purpose of the Study:

  • To accurately determine the 203Tl and 205Tl chemical shifts of TlNO3 at infinite dilution.
  • To investigate the influence of concentration and temperature on Tl chemical shifts.
  • To correlate Tl chemical shift behavior with ionic association in solution.

Main Methods:

  • Precise measurement of 203Tl and 205Tl NMR chemical shifts.
  • Experimental determination of chemical shift variations with varying solute concentration.
  • Temperature-dependent NMR measurements to assess Tl chemical shift behavior.

Main Results:

  • The chemical shift of TlNO3 at infinite dilution was accurately measured as -22.16 ppm for 203Tl and 0.75 ppm for 205Tl, relative to standard frequency ratios to proton.
  • The study quantified the dependence of thallium chemical shifts on concentration and temperature.
  • Observed Tl chemical shift variations were analyzed in the context of ionic association.

Conclusions:

  • Established precise reference values for 203Tl and 205Tl NMR spectroscopy.
  • Provided insights into the factors affecting Tl chemical shifts, aiding in spectral interpretation.
  • The findings facilitate more accurate and consistent referencing in thallium NMR studies.