Heteronuclear Spin-Spin Coupling on the NMReady-60PRO

Heteronuclear Spin-Spin Coupling on the NMReady-60PRO

Spin-spin coupling is an important facet of 1H NMR spectroscopy, as crucial details about the structure of a molecule are revealed based on the pattern of multiplets observed. In general, the signal for a group of equivalent protons will be split into a multiplet based on the n+1 rule, where nis the number of equivalent protons that are adjacent to the protons. For example, the signal of the CH2 protons in an ethyl group will be observed as a quartet (adjacent to three equivalent protons; 3+ 1) while the signal for the CH3protons in the same ethyl group will be a triplet (adjacent to two equivalent protons; 2+ 1).

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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:

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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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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!

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A bright application…

A bright application…

BODIPY dyes, which are boron difluoride compounds supported by dipyrrinato ligands, have gained recognition as being one of the more versatile fluorophores due to their superior photophysical properties.[1,2] BODIPY derivatives are used as stable functional dyes in several fields such as light harvesters, laser dyes, fluorescent switches, and biomolecular labels.[3-6] They gained popularity as biological probes due to the easy modification of the ligand framework, extension of the chromophore, and substitution of the fluorine atoms.6 Figure 1 shows some commercially available BODIPY dyes used as biological probes.

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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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The lightest metal with a heavyweight demand: Lithium

The lightest metal with a heavyweight demand: Lithium

Before the early 1950’s lithium was an ingredient found in Seven-up®; however, after concerns by the FDA it was removed from this popular beverage. Interestingly, about the same time it was found that lithium had antipsychotic properties, but it was only approved for human consumption in the 1970’s.[1] Despite being such a simple molecule lithium carbonate is still the most effective drug for the treatment of bipolar affective disorder! We don’t hear this side of the lithium history very often. In recent years this element has become very popular and its demand has increased considerably due to its widespread use in batteries for small electronic devices such as smart phones and laptops.[2]

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The Dangers of Making Too Many Assumptions. Electronegativity, Acidity, and Chemical Shift

The Dangers of Making Too Many Assumptions. Electronegativity, Acidity, and Chemical Shift

Last month (which you can see here), we learned about how an acidic proton behaves in a 1H NMR experiment, particularly when it’s surrounded by D2O. For example, when an H+ leaves CH3COOH to join an accommodating D2O molecule, the resulting acetate (H3CCOO–) segment is reasonably comfortable bearing that negative charge. This phenomenon is the reason the solution is “acidic” in the first place. But why is acetate so capable of dealing with this negative electronic charge?

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Boron NMR Spectroscopy

Boron NMR Spectroscopy

For my first blog I have decided to talk a little bit about boron because it’s a fascinating element that imparts remarkable properties to its compounds. And believe me, there are hundred of different compounds with very different properties containing boron centers. We find boron in compounds like boronic acids (A), boronic esters (B), and MIDA boronates (C), all of which are very popular in Suzuki coupling reactions to make new C–C bonds.  Another popular family of compounds containing boron are the BODIPY dyes (D). These derivatives, composed of a dipyrromethene ligand supporting a BF2 unit, are used as stable functional dyes in several fields, but their application as biomolecular labels is the most investigated by far.

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