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ACD/Labs Blog

Ryan Sasaki
I was flying home from Europe yesterday and was watching the Oscar award-winning movie “Good Will Hunting” starring Matt Damon, Robin Williams, Ben Affleck, and Minnie Driver: One thing I missed the first time I saw the movie, was a moment where Matt Damon’s character shows up at Minnie Driver’s dorm room to ask her...

Ryan Sasaki
PKC Pharmaceuticals is working very hard to try and not only remedy the issues that have come out of the Bosutinib issue described in previous posts and in other media outlets, but to also really understand what went wrong, what is out there, and how to clear the air on this issue. I believe they...

Ryan Sasaki
I’ve already described the Bosutinib fiasco in my last entry, and finished with a teaser that we would be back for more commentary on this topic. We plan a series of tests of our algorithms and systems to see if our software could have been used to prevent a situation like this. The main question...

Ryan Sasaki
For many years I have been looking for a high profile public case that represents a good example of why an automated NMR structure verification system can help prevent bad things from happening. We all know these types of examples exist, but they don’t generally become public knowledge. Yes, I’ve blogged about this topic many...

Arvin Moser
Coupling patterns that overlap can be deceptively simple. There are two possible coupling patterns for the CH2 signal at 3.39 ppm (top spectrum): a singlet or two ‘doublets’ (AB spin system) tilted towards each other. The bottom spectrum shows an example of two ‘doublets’ where the outer signals at 3.34 and 3.43 ppm are barely...

Arvin Moser
Coupling patterns can be deceptively simple. For an unknown compound, the expanded region of a 1H NMR spectrum below shows a signal at 3.39 ppm for a CH2 group. Is the coupling pattern for this two spin system a ‘true’ first-order singlet?

Arvin Moser
Part of the process of interpreting data from 2D NMR spectra is to adjust the intensity threshold in order to differentiate visually the signals from the noise. A certain level of cautious peak picking is needed so not to overlook a weak signal nor confuse a noisy region for a real signal. For an unknown...

Arvin Moser
Spectral data that exhibit weak signals (low S/N) can easily be misinterpreted. A good approach is to check the data against other data to confirm whether the signal is real or an artefact. For an unknown compound, the 1H -13C HSQC spectrum below is shown at two different intensity thresholds. The aromatic protons at 6.97...

Arvin Moser
With deuterated chloroform, the signals from the solvent can overlap with the signals from the unknown of interest. The following spectra are some examples one may encounter. In the expanded regions for each 13C NMR spectrum, Cases 1, 2, 3, 4 and 5 display a weak signal at ~76.8, 77.3, 77.5, 77.5, 77.5 ppm, respectively....

Arvin Moser
Solvent signals that overlap with signals from the unknown can be a hurdle in an elucidation. The energy wasted when misidentifying a signal can make an elucidation attempt wearisome and frustrating to put it mildly. Several 13C NMR spectra were collected in deuterated chloroform for a set of unknown compounds. Are any non-solvent signals evident...