Skip To Content

ACD/Labs Blog

Arvin Moser
‘How many signals are present?’ is such a simple question, and yet, it is a fundamental question to an elucidator. Mistaken a signal or overlook one and the elucidator can run the risk of wasting time and effort.   The 13C [1H] NMR spectrum below shows 3 discernible signals that are attributed to the solvent CDCl3. In...

Arvin Moser
When dealing with small sample concentrations of an unknown compound, the NMR region where a large solvent signal appears rarely gets a second look. However, a large NMR signal can easily obscure a small signal. From one elucidator to another, check the solvent signal for any structural signals. In the 13C [1H] NMR spectrum below,...

Arvin Moser
Based on experience, fused ring systems on an unknown structure tend to conjure up variations of odd connections. The possibilities can seem endless. The diagram, shown below, samples a subset of fused ring systems for a given dataset. It is important to note that although certain systems may be more appealing to the eye, it...

Arvin Moser
Socrates is known for saying ‘Know thyself’, along the same line, chemists should ‘Know thy instrument’. The example below is one such case. The 13C NMR [1H] spectrum below exhibits 6 signals. If an unknown compound comprises of 7 carbon atoms, then the following scenarios, or combinations thereof, are possible to account for missing or extra...

Arvin Moser
Structure elucidation by NMR involves a deep understanding of various technical aspects behind data acquisition. Being aware of how the instrument works can facilitate the process and reduce the aggravation. For today’s puzzle, an unknown compound is known to comprise of 7 carbon atoms and exhibit the following 13C NMR spectrum with 1H decoupling. How...

Arvin Moser
The goal of this puzzle is to determine the respective benzene ring systems that would exhibit the following 1H NMR spectrum. The number of substituted benzene ring systems that would exhibit the following 1H NMR spectrum is 3 (assuming no repeating units). The keys to solving this puzzle lie with the determination of which multiplets...

Arvin Moser
The goal of this puzzle is to resolve the ambiguity exhibited within a 2D NMR spectrum and thus provide the correct signal correlation. Although this exercise may seem a trivial one, it is important to go over the rationale when correlating one signal to another. For the following 1H-13C HSQC-DEPT NMR spectrum it is important...

Arvin Moser
The goal of this puzzle is to resolve the ambiguity exhibited within a 2D NMR spectrum and thus provide the correct signal correlation. The following 1H-13C HSQC-DEPT NMR spectrum shows two one-bond correlations linked to the 1H signals 2.75 and 3.50 ppm and two closely spaced 13C signals at 61.5 and 62.2 ppm. Does the...

Arvin Moser
The goal of this puzzle is to determine how the molecular formulae of the intermediates may assist in reasoning out the final product. In this puzzle, let’s consider the following one-pot synthetic reaction (solvents and additional reactants are not shown). The molecular formula (MF) and the RDBE information are also presented. The chemical reaction illustrates...