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.

Read More

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).

Read More

Lead NMR Spectroscopy

Lead NMR Spectroscopy

For many years tetraethyl lead was used as the principal fuel additive to enhance the octane rating of gasoline. In the mid-1970s the use of this substance was reduced because of the environmental hazards of lead and because it poisons catalytic converters. Nowadays, the main application of lead metal and lead oxide is in lead-acid batteries. In this application the cathode of the cell consists of lead dioxide packed on a metal grid and the anode is composed of lead metal. The electrochemical reaction is shown in the following equation:

Read More

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.

Read More

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).

Read More

Automation, Benchtop NMR and Industry

Automation, Benchtop NMR and Industry

Since it was discovered, the typical trend in NMR Spectroscopy has been towards higher field, evidenced by the rapid replacement of permanent magnets with supercons.[1]  Why?  Well, NMR Spectroscopy, of course, is one of the most information rich molecular spectroscopic techniques available, providing information of the type of nuclei, the number of those nuclei and even how they’re connected.  As you move to higher field you can immediately observe two things: 1) it’s easier to extract the aforementioned information because the resolution is better (i.e., more Hz/ppm dispersion) given the more favourable dispersion and 2) the data has inherently higher signal-to-noise ratio. 

 

Read More

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! 

Read More

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.

Read More

To apodize or not to apodize - the age old question

To apodize or not to apodize - the age old question

Are you familiar with the Apodization tool in Mnova? Apodization (also referred to as Weighting or Windowing) literally translates to ‘cutting off the feet’ from the original Greek. In this case, the ‘feet’ are the leakage or wiggles that appears when the NMR signal rapidly decays to zero. As such, apodization can enhance the resolution or the sensitivity (S/N ratio) in the spectrum and even remove truncation artefacts after data has been collected. This function is particularly useful for spectra acquired on a benchtop NMR instrument due to the lower S/N ratio compared to spectra collected on high-field instruments.

Read More

How strong was your coffee this morning?

How strong was your coffee this morning?

Who doesn’t want to start the day with a warm cup of coffee? Coffee has a stimulating effect on humans because of its caffeine content and for that reason it has become one of the most popular drinks in the world. Some clinical studies actually suggest that small amounts of caffeine everyday might be beneficial for adults. In this blog I am going to highlight an experiment done in collaboration with the Swager group at MIT using an organometallic complex to quantify the caffeine content in regular coffee without sample preparation!

Read More