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Arvin Moser
Zero filling is the process of adding a string of zeroes to the end of an FID. The following puzzle aims at understanding how zero filling impacts the line shape of a doublet. The following 1H NMR spectrum was collected with a total of 4K points (selective region is shown as spectrum E). Applying different...

Arvin Moser
The explanation offered herein covers one possible scenario to a complicated situation. Please note that other explanations are possible. The LC/MS data shows an unknown at 1.8 minutes exhibiting an [M+H]+ at m/z 260 and an [M-H]- at m/z 256. The difference of 4 mass units lends itself into a scenario of conflicting data. One...

Arvin Moser
The purpose of this puzzle is to examine data collected from multiple detectors with the hopes of sorting out the conflicting data surrounding the unknown. In an attempt to identify the structure for an unknown, UPLC data was collected using a C18 column with a run time of 2.2 minutes. The UV, ESI- and ESI+...

Arvin Moser
With each piece understood, a fragment(s) will emerge. From the 1H-13C HSQC spectrum, there are 3 CHn groups where n represents 1, 2 or 3 protons. The proton integrals indicate 2 CHs and 1 CH3 group. The CH3 group is observed as a singlet with 1H and 13C chemical shifts at 3.35 and 56.93 ppm;...

Arvin Moser
Piece by piece, fragment by fragment, an unknown compound is constructed until it is solved. The purpose of this puzzle is to focus on solving a fragment. The 1H-13C HSQC spectrum, shown below, is for an organic three-carbon fragment. The fragment is known to have 2 open sites that connect back to the structure. What...

Arvin Moser
As more information is needed to solve an unknown, it becomes useful to understand what information is available, make a hypothesis and then get to the grunt work of eliminating the unlikely candidates. Below is a summary explaining some of the information that can be extracted from the problem set. Given an unknown compound as...

Arvin Moser
It is fairly route for an elucidator investigating an unknown compound to relate data from multiple spectroscopies. This puzzle aims at establishing a molecular formula from a set of spectroscopic data. For an unknown organic, a ESI(neg.)-ToF mass spectrum for a singly-charged species and a 13C NMR spectrum are supplied below. In addition, the 1H...

Arvin Moser
Tying together the information from a 1H NMR and COSY spectrum, an elucidator can piece together certain fragments. Below is the solution for Logic Puzzle #21. The 1H NMR spectrum shows four aromatic methine multiplets at 6.61, 7.15, 7.22 and 7.58 ppm with coupling constants less than 2.5 Hz. The small coupling constants points to...

Arvin Moser
One of the trickiest parts of interpreting a 1H-1H COSY experiment is deciding how to classify the correlations. The goal of this puzzle is to assess the COSY correlations and narrow down a set of fragments that support the data. An expansion of the aromatic region of a 1H NMR spectrum shows four methine multiplets...

Arvin Moser
Diastereotopic protons that are also anisochronous exhibit different chemical shifts. As a general rule, the proximity of a chiral centre will influence the likelihood of diastereotopic proton signals being anisochronous. For the structure below, the CH2 labeled A is most likely to be anisochronous due to the adjacent chiral carbon. IUPAC: methyl 7-hydroxy-3,5-dioxo-7-phenylheptanoate InChi Key:...