Improve your learners’ NMR interpretation skills | news

Nuclear magnetic resonance (NMR) spectroscopy is a versatile tool used in many scientific fields, including chemistry, materials science, biology, and medicine.

Beyond structure elucidation, scientists use NMR spectroscopy to study reaction kinetics, reaction mechanisms, and intermolecular interactions. Interpreting NMR spectra is a key skill and consequently an integral component of teaching post-16 spectroscopy.

Students first encounter NMR spectra in high school, where they use it to determine the structures of simple organic molecules as part of problem-solving-style questions. As an information-rich technique, students can use many components of spectra to obtain structural information such as number, intensity and shape of signals, chemical shift, and J-coupling constants. While often challenging, these questions develop critical thinking skills.

In response to the limited number of academic resources available to practice NMR interpretation, researchers developed The NMR challenge, an online resource containing over 500 authentic NMR spectra of 200 organic compounds. Users can submit solutions using the structure drawing tool and confirm the correct solution.

In response to the limited number of educational resources available for practicing NMR interpretation, researchers developed the NMR Challenge (bit.ly/3XPsAJd), which contains more than 500 authentic NMR spectra of 200 organic compounds. Users can submit solutions using the structure drawing tool and confirm the correct solution.

They found several common mistakes that reflected students’ misunderstanding of the basic principles of NMR spectra.

The creators of the site organized the issues in a complex way. Ground state 148 1D spectra (1H, 13C and 19F) and suitable for secondary school students. Advanced mode contains 2D spectra. Within the basic and advanced levels, there is a further classification: easy, moderate and difficult.

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A New paper, the researchers who created the site – analyzed the success rates of all 200 tasks in the NMR Challenge, which contains 428,000 solutions from around the world, the largest database of answers to NMR tasks. Through this analysis, they identified several common mistakes that may reflect students’ misunderstanding of the basic principles of NMR spectra. The following three case studies summarize key findings.

Interpreting findings

Case Study 1: When considering isomeric esters, the researchers found that students were adept at using spectral information to identify molecular fragments such as the monosubstituted benzene ring, ethyl chain, and ester group. However, students were less able to use chemical shift values ​​to identify the linkage of these fragments.

Case study 2: When considering substitution patterns in substituted benzenes, students recognized only para-substituted structures well. A very complicated splitting method 1H spectrum for ortho- and meta-substituted benzenes may be due. However, you can use the number of signals 13C spectra distinguish homodisubstituted benzenes, which learners rarely consider.

Case Study 3: Many spectra also involve intramolecular interactions, for example, the formation of a hydrogen bond between an exchangeable hydrogen atom (for example, OH) and a hydrogen bond acceptor (for example, O in a carbonyl). Students often misidentified the increase in chemical change in exchangeable hydrogen 1Since H NMR spectra are identified, exact structures are not drawn.

Teaching Tips

Use The NMR challenge Recommend it for free in your teaching and as an independent practice for your students. It provides feedback on the submission and lets the user know if their answer is correct.

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The study provides further analysis Support information, including the most common mistakes. You can adapt this for additional classroom activity based on simulated-peer assessment.

The researchers identify several key observations to consider when teaching NMR spectroscopy:

  • Focus on tasks that consider isomeric structures, determine their structural fragments and connections.
  • Compare the spectra of esters with the spectra of their alcohol and carboxylic acid precursors.
  • While students were able to identify para-distributed benzene rings, ortho- and meta-distributed ones were more challenging. Help students become familiar with the multiplication of hydrogen atoms in these systems with plenty of exercises.

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