NMR Analysis

Important information for this page

This page contains a collection of information how to reference analytical data. We provide this page to describe the preferred formatting of analytical evaluations in the Chemotion repository. The given preferences follow standards of journals/publishers and other stakeholders wherever we could find them. Currently, in particular the format of the metadata of the analytical data (everything before "=") is not reviewed critically. If you have suggestions and comments: please let us know or provide your ideas via the issue tracking option. https://github.com/ComPlat/chemotion_saurus/issues Updated: 01.03.2024

Inline notation for ¹H NMR data

The inline notation gives a short summary of the metadata and a list of all signals or signals group (for signals that cannot be separated from each other). For each signal, the shift should be provided along with at least the following information given in parentheses: multiplet abbreviations, coupling constants, and number of atoms represented by each signal should be provided. (see example No 1)

Examples for desired formatting:

(1) Standard example:

¹H NMR (400 MHz, CDCl₃, 25 °C): δ [ppm] = 7.28 (dd, J = 1.6, 7.7 Hz, 1H), 7.14 (ddd, J = 8.2, 7.3, 1.6 Hz, 1H), 6.74–6.66 (m, 2H), 4.94 (s, 2H), 4.04 (br.s, 2H), 2.12 (s, 3H).

(2) Example for a solvent that needs signal definition:

¹H NMR (400 MHz, DMF-d₇ [2.75 ppm], 25 °C): δ [ppm] = 7.28 (dd, J = 1.6, 7.7 Hz, 1H), 7.14 (ddd, J = 8.2, 7.3, 1.6 Hz, 1H), 6.74–6.66 (m, 2H), 4.94 (s, 2H), 4.04 (br.s, 2H), 2.12 (s, 3H).

(3) Example with solvent ratio where CDCl₃ is used as a reference:

¹H NMR (400 MHz, CDCl₃/DMF-d7 5:1, 25 °C): δ [ppm] = 7.28 (dd, J = 1.6, 7.7 Hz, 1H), 7.14 (ddd, J = 8.2, 7.3, 1.6 Hz, 1H), 6.74–6.66 (m, 2H), 4.94 (s, 2H), 4.04 (br.s, 2H), 2.12 (s, 3H).

(4) Example with additional standard TMS:

¹H NMR (400 MHz, CDCl₃, 25 °C, TMS): δ [ppm] = 7.28 (dd, J = 1.6, 7.7 Hz, 1H), 7.14 (ddd, J = 8.2, 7.3, 1.6 Hz, 1H), 6.74–6.66 (m, 2H), 4.94 (s, 2H), 4.04 (br.s, 2H), 2.12 (s, 3H).

(5) Example with order of coupling constants, if available and required:

¹H NMR (400 MHz, DMF-d₇ [2.75 ppm], 25 °C): δ [ppm] = 7.28 (dd, J = 7.7, 1.6 Hz, 1H), 7.14 (ddd, ³ J = 8.2, ³ J = 7.3, ⁴ J = 1.6 Hz, 1H), 6.74–6.66 (m, 2H), 4.94 (s, 2H), 4.04 (br.s, 2H), 2.12 (s, 3H).

(6) Example with couplings which are not H,H couplings:

¹H NMR (400 MHz, DMF-d₇ [2.75 ppm], 25 °C): δ [ppm] = 7.28 (dd, J = 1.6, J = 7.7 Hz, 1H), 7.14 (ddd, ³ J = 8.2, ³ J _H,F = 7.3, ⁴ J = 1.6 Hz, 1H), 6.74–6.66 (m, 2H), 4.94 (s, 2H), 4.04 (br.s, 2H), 2.12(s, 3H).

(7) Example with missing protons and impurities:

¹H NMR (400 MHz, MeOD-d₄, 25 °C): δ [ppm] = 7.28 (dd, J = 1.6, J = 7.7 Hz, 1H), 7.14 (ddd, ³ J = 8.2, ³ J _H,F = 7.3, ⁴ J = 1.6 Hz, 1H), 6.74–6.66 (m, 2H), 4.94 (s, 2H), 4.04 (br.s, 2H), 2.12 (s, 3H). Missing signal (1H, OH) due to H/D exchange in MeOD. Impurities: 10% impurities due to the formation of the cis-isomer during the measurement of the sample.

(8) Example for isomers:

¹H NMR (500 MHz, MeOD-d₄ [3.31 ppm]): δ [ppm] = 13.23 (bs, 0.4H, CO₂H-isomer1), 12.98 (bs, 0.6H, CO₂H-isomer2), 8.24 (d, 0.6H, J = 1.5 Hz, CH-isomer2), 8.21 (d, 0.4H, J = 1.5 Hz, CH-isomer1), 3.30 (s, 3H, CH₃-isomer1+-isomer2) etc.

(9) Example for assignment according to option 1:

¹H NMR (250 MHz, CDCl₃): δ [ppm] = 7.08 (dd, J = 7.6, 1.2 Hz, 1H, H-5), 6.97 (ps.td, J = 7.6, 1.2 Hz, 1H, H-7), 6.63 (ps.td, J = 7.6, 1.2 Hz, 1H, H-6), 6.48 (dd, J = 7.6, 1.2 Hz, 1H, H-8), 3.85 (bs, 1H, NH), 3.40–3.22 (m, 2H, H-2), 3.02–2.84 (m, 1H, H-4), 2.07–1.92 (m, 1H, H_a-3), 1.76–1.61 (m, 1H, H_b-3), 1.30 (d, J = 7.0 Hz, 3H, CH₃).

(10) Example for assignment according to option 2:

¹H NMR (250 MHz, CDCl₃): δ [ppm] = 7.08 (dd, J = 7.6, 1.2 Hz, 1H, NHCCH), 6.97 (ps.td, J = 7.6, 1.2 Hz, 1H, CHCC H), 6.63 (ps.td, J = 7.6, 1.2 Hz, 1H, NHCCHCH), 6.48 (dd, J = 7.6, 1.2 Hz, 1H, CHCCHCH), 3.85 (bs, 1H, NH), 3.40–3.22 (m, 2H, NHCH ₂), 3.02–2.84 (m, 1H, CHCH₃), 2.07–1.92 (m, 1H, CH _a), 1.76–1.61 (m, 1H, CH_b), 1.30 (d, J = 7.0 Hz, 3H, CH₃).

(11) Example for assignment according to option 3:

¹H NMR (250 MHz, CDCl₃): δ [ppm] = 7.08 (dd, J = 7.6, 1.2 Hz, 1H, H_ar), 6.97 (ps.td, J = 7.6, 1.2 Hz, 1H, H _ar), 6.63 (ps.td, J = 7.6, 1.2 Hz, 1H_ar), 6.48 (dd, J = 7.6, 1.2 Hz, 1H, H_ar), 3.85 (bs, 1H, NH), 3.40–3.22 (m, 2H, H-2), 3.02–2.84 (m, 1H, H-4), 2.07–1.92 (m, 1H, H_a -3), 1.76–1.61 (m, 1H, H_b-3), 1.30 (d, J = 7.0 Hz, 3H, CH ₃).

Alternatives for giving metadata

The following ways to cite the metadata for NMR are preferred: ¹H NMR (400 MHz, CDCl₃ [7.27 ppm], ppm) δ = ¹H NMR (400 MHz, CDCl₃, 25 °C): δ [ppm] =

Explanation of metadata for ¹H NMR data

• In a standard example, the metadata includes the type of the NMR measurement and further details in brackets. The details consist of the resonant frequency, the solvent in which the sample is dissolved and the temperature of the sample.
• If a solvent is used as reference (most common method), the reference shift has to be set to the available standards. (Gottlieb et al. 1997), (Fulmer et al. 2010)
• If a solvent is used as reference and there are different options which signal to be used (e.g. THF-d8, DMF-d7, ethanol-d6, pyridine-d5, toluene-d8), the used reference shift has to be added (see example No 2).
• If solvent combinations are used in the NMR experiment, the respective solvents and their proportions must be indicated. Please define the ratio by integration of the solvents in the NMR. Please take care that the degree of deuteration of the solvents is considered (see example No 3).
• If TMS is used as reference, "TMS" must be added to the parentheses (see example No 4). It is assumed that in this case the reference shift is set to 0.00 ppm.

Details of NMR data formatting - ¹H NMR signals

• Signal shifts are given from low field to high field.
• Signal details are given in parentheses in the following order: (1) multiplet abbreviations, (2) coupling constant, (3) number of atoms represented by the signal, (4) signal to atom assignment (optional, please refer to examples No 8 and No 9 regarding assignment styles).
• Signals should be reported to the nearest 0.01 ppm.

Multiplicity and coupling constants

• Each signal has to be given with the identified multiplicity and coupling constant(s) for well-resolved peaks.
• If the multiplicity is "m" (= multiplet), the signal has to be given as a range, e.g. 6.74–6.66 (m, 2H).
• Omit spaces while giving ranges for multiplets and use the "long minus" or "en dash": 6.74–6.66 (m, 2H). Hint: use the symbol "magic wand" for an automated formatting.
• Please use italic style for "J", add a space before and after "=", e.g. J = 2.2 Hz
• Coupling constants are given in the following order: large to small.
• Please give the coupling constant with an accuracy of 0.1 Hz.
• Mutually coupled protons in 1H NMR spectra must be quoted with precisely matching J values to assist thorough interpretation.
• Use the following abbreviations for defining the multiplicity of a signal: multiplet (m), singlet (s), doublet (d), triplet (t), quartet (q), quintet, sextet, septet, octet, and nonet. For further more complex signals, please see: https://www.chem.uci.edu/~jsnowick/groupweb/files/MultipletGuideV4.pdf
• Use "br." in addition for defining broadly shaped signals: br.s, br.t
• Indicate if a detected multiplicity does not correspond to the expected multiplicity (due to equivalent protons) and is observed due to coincidentally equal coupling constants: ps.t
• Range of the coupling: please give the range of the coupling (= distance in bonds) if known. If the range is given, the format for giving coupling constants should be changed to example No 5.
• If there are other couplings than H,H couplings, this needs to be indicated in the inline notation according to example No 6.

Number of protons

• Amount of protons is given without space: 1H instead of 1 H
• Missing signals: If there are missing signals due to H/D exchange, line broadening or signal overlap this needs to be stated as additional information to the analysis as in example No 7. Proton and carbon spectra will be automatically validated by the number of protons and carbons given in the analysis in comparison with the number of atoms given by the sum formula. Please use the following standard phrases if applicable: -- Missing signal (1H, OH) due to H/D exchange in MeOD -- Missing signals (2H, H-2) due to line broadening -- Missing signal (1H, H-7) due to overlap of signal with solvent Important with respect to the format: please add the information on the number and type of missing signals in brackets and use a comma to separate from other information such as the assignment within the bracket (1H, xx).

** Description for compounds that are obtained as mixtures of isomers and cannot be separated**

• Please give the number of protons per signal to achieve 1H/proton as combination of all isomers, see example No 8.

Assignments

Wherever possible, assignments should be given -but are not mandatory. Following, assignments are described for the example (S)-4-methyl-1,2,3,4-tetrahydroquinoline. If the assignments are given, they are added as the last part of the information in parentheses.

Option 1 for giving explicit and clear assignments: The assignment of signals to atoms by number (see example No 9) is valid in two cases:

• If one has a standardized numbering of the compound according to IUPAC and the numbering is clear with the structure and the use of the standardized chemical name as part of the description,
• If one provides a numbered structure as image format. This image has to be given as an additional dataset for the analysis.

Option 2 for giving explicit and clear assignments: The assignment can be done by giving fragments that describe the chemical environment of the proton sufficiently. In that case, the assigned nucleus is indicated by italicization. In the example of (S)-4-methyl-1,2,3,4-tetrahydroquinoline, the assignment can be given as described in example No 10.

Option 3 In some cases, an explicit and clear assignment might be (partly) difficult. In such cases, the assignment of groups can be done by giving fragment descriptions such as "ar" (=aryl). For the example of (S)-4-methyl-1,2,3,4-tetrahydroquinoline, the assignment can be given as described in example No 11.

Additional aspects important for the data in Chemotion repository

• Integrate all peaks in the ¹H NMR arising from the compound.
• The largest peak in the ¹H NMR spectrum should be full scale and arise from the analyte, not from the solvent or an impurity.
• NMR spectra should have sufficiently high signal-to-noise ratios so that all peaks can be adequately resolved.
• The minimum chemical shift range for ¹H NMR spectra should be −1 to 10 ppm and for ¹³C NMR spectra −10 to 200 ppm.

Impurities: Please check the purity of your compounds carefully before submitting your data. If the spectra contain by-products or solvents not mentioned in the content/description, the data will be returned for revision or rejected.
If your spectra contain impurities that cannot be eliminated, please indicate the percentage and origin (if known) of these impurities in all submitted analyses. This information is not part of the inline notation and will therefore not be included in the analytical data exported to journal supplementary information files. See the following statements and example No 7 for the correct way to report impurities:
-- Impurities: 10% impurities due to the formation of the cis-isomer during the measurement of the sample. -- Impurities: 1% ethyl acetate, unknown impurities at 1.11–2.22 ppm and 3.33 ppm. -- Impurities: approx. 5% impurities at 7.66 ppm and 2.44 ppm due to an unknown by-product.
Keep in mind that these must also be considered in the yield calculations.

Inline notation for ¹³C NMR data

The inline notation gives a short summary of the metadata and a list of all signals or signals group (for signals that cannot be separated from each other). For each signal, the shift should be provided along with at least the following information given in parentheses: multiplet abbreviations, coupling constants, and number of atoms represented by each signal should be provided. (see example No 1)

Examples for desired formatting:

(1) Standard example:

¹³C NMR (100 MHz, CDCl₃, 25 °C): δ [ppm] = (...), 129.5, 126.7 (2C), (...).

Explanation of metadata for ¹³C NMR data

see chapter "Explanation of metadata for ¹H NMR data" and example No 1

Details of NMR data formatting - ¹³C NMR signals

• Signal shifts are given from low field to high field.
• Signal details are given in parentheses in the following order: (1) multiplet abbreviations, (2) coupling constant, (3) number of atoms represented by the signal, (4) signal to atom assignment (optional, please refer to examples No xx and No xx regarding assignment styles).
• Signals should be reported to the nearest 0.1 ppm.
• Don't forget to give coupling constants for ¹³C NMR data if applicable (e.g. C-F coupling, C-P coupling).
• Give the amount of carbons if there is more than one carbon to be assigned to one signal (example No 1). Please assign atoms to the signals whenever possible and reasonable. In cases where the assignment of protons (e.g. of 6 protons for two methyl groups in a symmetrical compound) to one signal in 1H NMR is clear - the assignment of the corresponding (in that case 2) carbons to one signal in 13C NMR should be done as well.
• Isomers: If you can assign all signals: please give separate lists of 13C assignments for isomer 1 and isomer 2 and separate both analytical descriptions with the text-fragment: "Other isomer:"
• Rotamers: List all signals with their ratio that contributes to 1C. The sum of all ¹³C signals should correspond to the overall number of ¹³C atoms in the molecule.

Important for entries in the repository:

• If the assignment of signals to atoms in isomers (only then) is not possible, please list all signals, assign as many as you can and submit the measurement by changing the "process". Isomers which can't be assigned need to be reset to the unspecified term "process". Please add the info "due to an inseparable mixture of isomers, the total amount of protons/carbons could not be confirmed by a clear assignment" to the end of your analysis.

¹⁹F NMR spectroscopy data

If the compound contains Fluorine atoms, the analysis set should contain ¹⁹F NMR data. ¹⁹F NMR data should be given with the same information and formatting as described in the data and metadatasection of ¹H NMR data. Differences are:

• Signals should be reported to the nearest 0.1 ppm.

³¹P NMR spectroscopy data

If the compound contains phosphorus, the analysis set should contain ³¹P NMR data. ³¹P NMR data should be given with the same information and formatting as described in the data and metadatasection of ¹H NMR data. Differences are:

• Signals should be reported to the nearest 0.1 ppm.

¹¹B NMR spectroscopy data

If the compound contains boron, the analysis set should contain ¹¹B NMR data. ¹¹B NMR data should be given with the same information and formatting as described in the data and metadatasection of ¹H NMR data. Differences are:

• Signals should be reported to the nearest 0.1 ppm.
• Take care: borosilicate glass used for NMR tubes give a broad signal in ¹¹B NMR data.

additional information

Chemical shift values should be included for all peaks arising from the compound in the 1H and 13C spectra
Display the NMR baseline and include the minimum chemical shift range:
-1-9 ppm for 1H spectra
-10-190 ppm for 13C spectra
Extended range for functional groups that resonate from 9-14 ppm