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ACD/Labs Blog

Ryan Sasaki
As I am closely approaching my one year anniversary of this blog (how time flies!), Arvin’s post entitled, “How Do I Know if my Unknown Contains a Fluorine Atom”,  reminded me an X-nuclei related post from almost a year ago. In that post I highlighted a best practice document written by Gary Martin for acquiring...

Arvin Moser
Ideally, identifying whether a fluorine atom(s) is present is as simple as acquiring a 19F NMR. However, running ‘uncommon’ experiments is not usually my first step in an elucidation (MDE). Imagine a scenario where the elucidator is unsure whether fluorine is present. He/she acquires a 19F NMR and sees no 19F resonances. Therefore the extra...

Arvin Moser
When faced with a crowded region in a 1H NMR spectrum, a 2D NMR experiment can assist in removing the ambiguity and in narrowing down the proton count. For the 1H NMR spectrum below, Multiplet F (the region between 1.4 to 1.8 ppm) displays an integral of 6.71. Although several factors may contrbute to the...

Arvin Moser
A very useful bit of information on the proton count comes from integrating a 1H NMR spectrum. However, overlapping resonances can make integration less than straightforward and in some cases ambiguous. Integration involves the following decisions to be made by the elucidator: which resonances to integrate, where the integral begins and ends, and what the...

Ryan Sasaki
I had a conversation with Geoff, one of my ACD/Labs colleagues just yesterday. He provided me with a great quote from a person he was talking to about software and usability. He said: "User-Friendly…hrmph…what that means to me is: love it for the first week, hate it forever!" I think that’s a great quote. I...

Arvin Moser
Here is a lesson I learnt over time while working on small molecules—my Elucidation Evolution. Thinking back to when I started doing elucidations of unknowns, my mindset was to collect loads of data (NMR, MS, IR, etc.) whether I needed it or not. Initially inexperienced, I was extracting bits and pieces of information from various...

Arvin Moser
In a substituted benzene ring, aromatic protons that are in the meta position can exhibit coupling to each other. This is referred to as meta or 4J coupling. The coupling pattern is typically a doublet with a coupling constant of ~2 Hz. On the contrary, a spectrum without any meta coupling indicates a lack of protons...

Arvin Moser
Looking for the next big pharmaceutical drug among natural products is a growing endeavour. However, a common drawback to working with natural products is the limited amount of sample. With a sample limitation, acquiring a 13C NMR spectrum within a reasonable time can be an issue. Rather than wasting instrument time on a 13C NMR,...

Arvin Moser
The second-order effects (also known as tilting or roofing) exhibited by multiplets can be used to identify multiplets coupled to each other. The 1H NMR spectrum below illustrates an example of strong coupling among three multiplets. The peak intensities across Multiplets A and B are different, that is, the peak on the right side of...

Ryan Sasaki
Do you currently use NMR for quantitative analysis? At the University of Ottawa NMR Facility Blog, Glenn Facey provides some acquisition tips for 1H NMR spectra. If you perform quantitative analysis on your spectra, how do you do it? Do you do it manually by hand, or do you use some software to help? I...