Beyond Structural Elucidation - Introduction to qNMR Part III - Relaxation Delays

Beyond Structural Elucidation - Introduction to qNMR Part III - Relaxation Delays

In this blog, Part III of the qNMR series, I will be addressing relaxation and why it's important for quantitative nuclear magnetic resonance (qNMR) experiments. If this is your first time reading about qNMR and would like to know more, please check out our other posts where you can find a general introduction to qNMR as well as information for the types of calibrants available for qNMR experiments.

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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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Attached Proton Test, an 'APT' experiment for structural elucidation

Attached Proton Test, an 'APT' experiment for structural elucidation

A key step towards elucidating structures with NMR spectroscopy is the assignment of signals to specific groups within the molecule being analyzed. Two experiments, DEPT (Distortionless Enhancement by Polarization Transfer) and APT (Attached Proton Test), are typically used to aid this process with 13C NMR spectra.1 Both experiments are similar in that the number of attached protons (i.e. the multiplicity) is revealed by the phase of the 13C NMR signals. The key difference between the DEPT and APT experiment is that signals for quaternary carbons are observed in the APT experiment.

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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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Nucleophilic Substitution Reactions and Benchtop NMR

Nucleophilic Substitution Reactions and Benchtop NMR

Nucleophilic substitution reactions are frequently performed as an experiment in undergraduate organic chemistry courses. Reactions taking place at saturated carbons are mainly classified as SN1 or SN2, where S stands for substitution, N for nucleophilic, and the number indicates the molecularity of the reaction (1 for a unimolecular process, 2 for a bimolecular process). In the SN2 reaction the attack of the nucleophile and elimination of the leaving group occur simultaneously in a concerted process and its rate is proportional to the concentration of both the alkyl halide and the nucleophile.

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2017 Year in Review

2017 Year in Review

With great advances in areas such as metabolomics, quantitative NMR, and online analysis, 2017 was a very exciting year for NMR in general, but specifically so for Benchtop NMR! Benchtop NMR has continued to make NMR, one of the strongest characterization techniques, become a mainstream staple in teaching and research laboratories. As users realize how easy it is to incorporate the NMReady-60 spectrometers into their laboratories, they have continued to breakthrough into new and exciting applications.

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To D2O or not to D2O?

To D2O or not to D2O?

In the average case one can simply dissolve an analyte in an appropriate deuterated solvent and acquire a simple 1D spectrum to obtain all the required structural information.  However, sometimes doing so may not provide you with all of the information you need!  It is not uncommon to encounter labile proton peaks in functional groups such as alcohols, amines, amides, and carboxylic acids. 

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'Hop' off the Diagonal: COSY spectrum of α-humulene

'Hop' off the Diagonal: COSY spectrum of α-humulene

NMR spectroscopy is by far the most useful characterization technique in organic chemistry, especially if you have to elucidate the structure or configuration of your products. Arguably, 2D experiments such as COSY, HSQC, and HMBC have simplified this task tremendously. In this post I wanted to highlight the COSY of α-humulene. 

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