2D NMR Experiments - HETCOR

2D NMR Experiments -  HETCOR

2D NMR experiments can provide an abundance of information for the structural elucidation of chemical compounds. An older example of a 2D experiment is the heteronuclear correlation (HETCOR) sequence. In this experiment, two different nuclei (usually 13C and1H) are correlated through single bond spin-spin coupling, revealing which proton and carbon groups are bonded to each other.

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Two solvents, two different spectra - Aromatic Solvent Induced Shifts

In my opinion, one of the most helpful papers[1]in the field of NMR spectroscopy in Organic Chemistry consists of ‘just’ two tables. In these, the chemical shifts (1Hand 13C) of as many as forty-two common impurities in twelve different deuterated solvents are listed. This is gold! Why? We know, that the signals of one and the same compound can show a rather high discrepancy in its chemical shifts in different solvents. But did you also know, that there is a concept called Aromatic Solvent Induced Shifts (ASIS), which benefits from this fact? 

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Getting COSY with the TOCSY Experiment

Getting COSY with the TOCSY Experiment

2D NMR experiments can provide a wealth of information to aid in the structural elucidation of chemical compounds. Of the many 2D NMR experiments available, the homonuclear correlation spectroscopy (COSY) sequence is one of the most popular and is used to identify which spin systems are directly coupled to each other. As an example, the 1H-1H COSY spectrum of 1-propanol recorded on the NMReady-60 is shown below in Figure 1.

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What's the 'ism' of today? Keto-Enol Tautomerism

What's the 'ism' of today? Keto-Enol Tautomerism

Tautomers are constitutional isomers that interconvert into each other by an exchange reaction, most commonly a proton transfer. Such two isomers can for example be a ketone and an enol. Keto-enol tautomerism (KET) becomes possible when there are hydrogen atoms adjacent to a carbonyl group (these hydrogen atoms are called α hydrogens). This tautomerism is depicted in Scheme 1 and is also discussed more here.

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Enantiomers – Image | Mirror Image

Enantiomers – Image | Mirror Image

Chirality has a huge impact on the chemistry of a molecule. Due to potentially different physiological effects, pharmaceutical compounds are often used as enantiomerically pure compounds. One enantiomer can act as a healing agent, the other might be toxic to humans. Crazy, right? It makes sense, if you think of how pharmaceuticals work in principle. They bind to receptors, which trigger something in the brain or somewhere else in the human body. These receptors have a special chemical specificity and only the active compounds fit and bind correctly with it. A receptor is a 3D body and thereby is dependent on the stereochemistry of the compounds.

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HSQC – Revealing the direct-bonded proton-carbon instrument

HSQC – Revealing the direct-bonded proton-carbon instrument

2D NMR experiments provide chemists with evidence to clarify and confirm resonance assignment.  Nowadays every organic chemist uses these experiments called COSY, HMBC and HSQC as routine analytics. Basically, with 2D experiments you correlate some kind of information between two 1D spectra. If we correlate two 1D spectra of the same nucleus we are dealing with homonuclear 2D NMR experiments. The most famous representative of this group is the COSY experiment (find theory here and application here).

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Evans Method with NMReady-60 for understanding 1H NMR of Paramagnetic Compounds

Evans Method with NMReady-60 for understanding 1H NMR of Paramagnetic Compounds

Due to the presence of unpaired d electrons in their metal ions, many transition metal complexes are paramagnetic. The unpaired electrons have a magnetic dipole moment due to their spin and act like tiny magnets, resulting in a small net attraction to an externally applied magnetic field. Unsurprisingly, the presence of paramagnetic ions has significant effects on both the chemical shift and lineshape of the 1H NMR spectrum of transition metal complexes, with the chemical shift range being much wider along with broadening of the signals.

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Unlocking the Key to Enzymes: Studying Enzyme Kinetics

Unlocking the Key to Enzymes: Studying Enzyme Kinetics

By virtue of its quantitative nature, NMR spectroscopy is increasingly becoming the method of choice to monitor a reaction and determine its kinetic parameters. We’ve demonstrated the ability of the NMReady-60 to monitor a reaction and subsequently extract kinetic parameters in a previous blog post. In this blog post, I’d like to show how the NMReady-60 can be used to study enzyme kinetics. Adapted from a Journal of Chemical Education article published by Olsen and Giles, the enzymatic hydrolysis of N-acetyl-DL-methionine by porcine acylase was studied.

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Spine disease? No, just a rigid backbone, but it keeps from flippin’ the ring!

Spine disease? No, just a rigid backbone, but it keeps from flippin’ the ring!

For this one I must begin with a little personal background information due to my special relationship to the scaffold of the target compound. During my diploma thesis I investigated gold(I) phosphine complexes as catalysts for the intermolecular hydroamidation of olefins.[1] I found that dinuclear gold complex showed superior reaction times and yields compared to mononuclear complexes, like Ph3PAuCl. This particular dinuclear complex [xantphos(AuCl)2] (1) was kicking the reaction of norbornene (2) and tosyl amide (3) and made my first academic publication possible (scheme 1).

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Eat Your Heart Out Mass Spec: Measuring 10B/11B Isotopic Ratio by NMR Spectroscopy

Eat Your Heart Out Mass Spec: Measuring 10B/11B Isotopic Ratio by NMR Spectroscopy

As I’m sure the readers of this blog know, NMR spectroscopy is used widely across all branches of chemistry due to its powerful structure elucidation capabilities and the inherently quantitative nature of the technique.  Organic relies primarily on 1H/13C  experiments where as inorganic chemistry can expand to other nuclei, like 31P and 11B.  However, there are many other applications for NMR other than just structural elucidation.  Perhaps a lesser known application of NMR spectroscopy, is its ability to determine the isotopic ratio of elements! In this blog post I would like to demonstrate a novel method to determine the 10B/11B isotopic ratio using our NMReady-60e and 1H NMR spectra! 

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