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Organic Structure Elucidation

This document discusses resources available for structure elucidation of organic molecules at the Magnetic Resonance Research Center of the University of Notre Dame and gives brief recommendations.

Contents

• Sample Requirements

• Spectrometers

• Experiment Choice and Parameters

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Sample Requirements

Here are sample requirements for acquisition of necessary spectral data on Bruker 800 with a room-temperature probe (TXI).

 

1. Minimum advisable concentration:

• proton detection:  1-5 mM (millimol/L)
• carbon detection: 10+ mM

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2. Required sample volume:

• Normal tube = 0.6 ml
• Shigemi tube = 0.3 ml

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3. How much compound in milligrams will I need?

[Weight of your compound, mg] =   [concentration, mM]  *  [molecular weight, g/mol] * [sample volume, ml] /1000

Example:

To make a sample of 650 Da compound in a Shigemi tube, I need to have  
5 mM * 650 g/mol * 0.3 ml /1000  = 0.98 mg

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4. Stability

• The sample must be stable at room temperature for, at least, 24 hours.
• If the sample is unstable, you should use multi-block acquisition (contact Evgenii Kovrigin for instructions)

 

 

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Spectrometers

As of 2/2/2022, we recommend

• proton detection: Bruker 800 MHz with a TXI probe

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• carbon detection: Bruker 800 with a BBO probe or Bruker 500 or Varian 600 with broadband probes. Bruker 800 with TXI probe has lower carbon sensitivity but is still useful for trial carbon spectra.

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• IMPORTANT NOTE: Data of similar quality may be obtained on Bruker 500 or Varian 600 as on Bruker 800 with BBO probe but resolving closely spaced peaks of stereoisomers will still be more difficult than at the 800 MHz.

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Experiment Choice and Parameters

For detailed planning of your structure determination experiments, you should request a meeting with Dr. Evgenii Kovrigin.

Here are the publications you have to read:

1. Analysis of cross-correlations and structure elucidation; parameters of acquisition
   Burns and Reynolds, "MInimizing risk of deducing woring natural product structures from NMR data", Magn Reson Chem, 2021, 59: 500-533

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2. High-Resolution NMR Techniques in Organic Chemistry, 3rd Edition, by Timothy D.W. Claridge. Elsevier Science (May 27, 2016), ISBN-10 ‏ : ‎ 0080999867, ISBN-13 ‏ : ‎ 978-0080999869

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3. Burns DC, Reynolds WF, Optimizing NMR Methods for Structure Elucidation, Series: New Developments in NMR vol. 17, Royal Society of Chemistry, 2019

The following document is a brief summary of the workflow used at MRRC:   Structure Elucidation

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