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Chemical Shift: Internal References and Solvent Effects01:17

Chemical Shift: Internal References and Solvent Effects

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...
¹H NMR: Interpreting Distorted and Overlapping Signals01:02

¹H NMR: Interpreting Distorted and Overlapping Signals

Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
Mass Spectrum: Interpretation01:24

Mass Spectrum: Interpretation

An unknown compound can be established by identifying the molecular ion peak in the mass spectrum. The molecular ion peak is often weak or absent due to the predominance of fragmentation in high-energy electron beams. In such cases, a soft-energy electron beam can be used to scan the spectrum to enhance the intensity of the molecular ion peak. Additionally, chemical ionization, field ionization, and desorption ionization spectra are used to obtain a relatively intense molecular ion peak.To...
High-Resolution Mass Spectrometry (HRMS)01:15

High-Resolution Mass Spectrometry (HRMS)

The resolution of a mass spectrometer depends on the efficiency of separating ions with different ion masses. The mass of an atom is approximated to the sum of the masses of protons and neutrons inside, considering the masses of protons and neutrons as equal. However, the masses of the proton (1.6726 × 10−24 g) and neutron (1.6749 × 10−24 g) are not truly equal. There is a minor error in the expression of atomic masses relative to the simplest atom of hydrogen. For example, the mass of helium...
NMR Spectroscopy: Chemical Shift Overview01:15

NMR Spectroscopy: Chemical Shift Overview

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...
Polymers: Molecular Weight Distribution01:10

Polymers: Molecular Weight Distribution

For any given polymer, the weight average molecular weight (Mw) is higher than, if not equal to, the number average molecular weight (Mn). The only situation in which the weight average molecular weight and the number average molecular weight are equal is when a polymer consists only of chains with equal molecular weight. However, this never happens in a synthetic polymer, since it is difficult to control the polymerization process up to a molecular level with accuracy to a hundred percent.

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関連する実験動画

Updated: Jun 24, 2026

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
14:55

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy

Published on: September 17, 2017

内部参照拡散順序によるNMRスペクトロスコーピー (DOSY) による配列重量予測

Deyu Li1, Gerald Kagan, Russell Hopson

  • 1Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA.

Journal of the American Chemical Society
|March 28, 2009
PubMed
まとめ
この要約は機械生成です。

この研究では,未知の分子 (FW) の配方量 (FW) を決定するための内部参照相関DOSY法が導入されています. この実用的なテクニックは,種を様々な溶媒と濃度で正確に特徴付けます.

さらに関連する動画

Application and Methodology of the Non-destructive 19F Time-domain NMR Technique to Measure the Content in Fluorine-containing Drug Products
09:24

Application and Methodology of the Non-destructive 19F Time-domain NMR Technique to Measure the Content in Fluorine-containing Drug Products

Published on: August 22, 2017

関連する実験動画

Last Updated: Jun 24, 2026

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
14:55

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy

Published on: September 17, 2017

Application and Methodology of the Non-destructive 19F Time-domain NMR Technique to Measure the Content in Fluorine-containing Drug Products
09:24

Application and Methodology of the Non-destructive 19F Time-domain NMR Technique to Measure the Content in Fluorine-containing Drug Products

Published on: August 22, 2017

科学分野:

  • アナリティカル・ケミストリー (Analytical Chemistry) とは
  • 物理化学 物理化学
  • 有機化学 オーガニック・ケミストリー

背景:

  • 配列重量 (FW) は,反応性中間物質と有機金属複合体の特徴づけに不可欠です.
  • FWの正確な決定は,組成,集積,および溶解状態を理解するのに役立ちます.
  • 既存の方法は,様々な溶媒および濃度条件において,限界がある可能性があります.

研究 の 目的:

  • FW.を計算するための内部参照相関DOSYメソッドを開発し,検証する.
  • 異なる溶媒と濃度の方法の正確性と適用性を評価する.
  • この新しい特徴付け技術を実装する上で成功するためのガイドラインを提供すること.

主な方法:

  • 内部基準規格を備えた,利用された拡散オーダー光譜法 (DOSY).
  • 未知の種の配列重量 (FW) を計算するために,相関したDOSYを使用した.
  • 溶媒,濃度,溶液の粘度が精度に影響することを調査した.

主要な成果:

  • 小分子 (DIPA) と有機金属複合体 (集積1) の両方に優れた相関が得られました.
  • 相対的な拡散率が溶液粘度と逆相関し,ストークス-アインシュタイン方程式と一致することを実証した.
  • 予測の精度 (r^2,%差) は,密度変化と関連しており,密度が減少するにつれて改善します.

結論:

  • 内部参照相関DOSYメソッドは,FWの決定のための実用的で正確なアプローチを提供します.
  • この方法は,さまざまな溶液状態にある様々な分子や複合体に適用できる多用途です.
  • このテクニックは,未知の化学物質の種類を特徴付けるための貴重なツールを提供します.