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ACD/Labs Blog

Ryan Sasaki
This is a continuation of a series of posts that began here. In my last post, I promised to address how, by simply spending 2 minutes re-cutting their integrals, a chemist can extract much more valuable information from their spectra. The #1 thing in our NMR software that blows chemists away is the production of...

Ryan Sasaki
This is a continuation of a series of posts that began here. Here’s a short and sweet one. In my last post, I talked about how having immediate access to the processed data is something that most chemists like. From there, for a lot of chemists the workflow is very simple. Let’s just get the...

Arvin Moser
One of the trickiest parts of interpreting a 1H-13C HMBC is deciding whether a 13C resonance is coinciding with another 13C resonance, i.e. overlapping 13C peaks. A past blog, Part 1, describes a specific case where the possibility of two coinciding 13C resonances can be deciphered based on a high carbon correlation count. Herein, we...

Ryan Sasaki
This is a continuation of a series of posts that began here. I learned an interesting lesson a few years ago when I was presenting our software on-site to a group of chemists. I began the demonstration by opening up an FID. The response from most of the room was a mix of confusion as...

Arvin Moser
When dealing with a structure elucidation problem where little or no previous fragment information exists, the number of possibilities can seem endless. Although typically one envisions a neutral compound for the unknown, ionic compounds, such as salts and zwitterions, are also just as likely and thus can add to the complex nature of an elucidation....

Arvin Moser
The approach behind solving a structure elucidation problem is very similar to attempting a math problem or working on a jigsaw puzzle. This similar mental framework shares a basis, but not limited to, on understanding the basic rules that define the problem, and in some cases the creativity and flexibility to redefine the problem. When...

Arvin Moser
Chemical shift information offers a clue into an atom’s hybridization state. For example, carbon atoms with a carbon chemical shift greater than 90 ppm are typically considered as sp2 carbons. If 4 sp2 carbons are present, one can infer 2 alkene pairs. Five sp2 carbons and an available oxygen and nitrogen atom suggest the possibility...

Arvin Moser
A common misinterpretation of 2D NMR data can occur when dealing with weak correlations. Weak correlations are commonly introduced in how the sample is prepared or how the data is collected or processed. Examining the spectrum down to level of the density matrix can ensure all correlations are picked up. The 1H-13C HMQC below shows...

Arvin Moser
A previous blog described how a sodiated ion peak can be used to locate or calculate the molecular ion for an unknown compound. In a similar fashion, the dimer ion peak can be used to identify the mass of the unknown even if the molecular ion is no visible. The ESI+ MS data below shows...

Arvin Moser
In addition to using chemical shift information to ascertain a carbon’s proton count (i.e. C, CH, CH2 or CH3), 13C NMR experiments can be set up in a variety of ways to assist with this process. The following simulated spectra compare a variety of 13C NMR experiments for aspartame. Please note that there are variations...

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