NMR Shift Predictor Inputs
The page uses a single stacked layout, while the input grid expands to three columns on large screens, two on medium screens, and one on mobile.
Plotly Graph
The graph shows the base shift, each correction, and the final predicted position.
Formula Used
This calculator uses an additive correction model. It starts from a base chemical shift for a chosen proton or carbon environment. It then adds or subtracts structural corrections that represent deshielding or shielding influences.
Base shift
The base shift represents a typical literature-centered region for a chosen site class, such as alkyl proton, aromatic proton, ether carbon, or carbonyl carbon.
Corrections
Each correction modifies the base value. Deshielding factors raise the ppm value. Shielding factors lower it. The calculator uses simple fixed increments so the result stays transparent and explainable.
Uncertainty window
The estimated range widens when more modifiers are used. That helps reflect the broader spread often seen in real spectra, especially for exchangeable protons and highly substituted carbon sites.
How to Use This Calculator
- Select whether you want a 1H or 13C estimate.
- Choose the base site class that best matches the atom you are studying.
- Add only the extra corrections that are not already captured by the base site.
- Press Calculate NMR Shift to show the result above the form.
- Review the predicted ppm, range, confidence, and interpretation.
- Use the Plotly graph to see how each correction moved the final value.
- Export the result with the CSV or PDF buttons.
- Compare the estimate with your real spectrum and confirm using splitting, integration, and reference data.
Example Data Table
These sample rows show how the additive model can move a signal from its base site reference into a more realistic range.
| Nucleus | Example Site | Base Shift | Total Correction | Predicted Shift | Estimated Range |
|---|---|---|---|---|---|
| 1H | Benzylic proton with extra oxygen influence | 2.35 ppm | +1.05 ppm | 3.40 ppm | 3.20 - 3.60 ppm |
| 1H | Vinylic proton near a carbonyl group | 5.35 ppm | +0.70 ppm | 6.05 ppm | 5.78 - 6.32 ppm |
| 1H | Carboxylic acid proton with strong hydrogen bonding | 11.20 ppm | +1.25 ppm | 12.45 ppm | 11.86 - 13.04 ppm |
| 13C | Ether carbon attached to oxygen | 65.00 ppm | +6.00 ppm | 71.00 ppm | 68.95 - 73.05 ppm |
| 13C | Conjugated ketone carbonyl carbon | 200.00 ppm | +5.00 ppm | 205.00 ppm | 202.20 - 207.80 ppm |
FAQs
What does this calculator estimate?
It estimates educational 1H and 13C chemical shifts using an additive correction model. It combines a base environment shift with structural and environmental adjustments.
Can this replace full spectral analysis?
No. Real NMR interpretation also depends on coupling, integration, symmetry, concentration, temperature, impurities, and instrument settings. Use this as a guided predictor.
Why do O-H and N-H peaks vary so much?
Exchangeable protons respond strongly to solvent, concentration, hydrogen bonding, and temperature. Their peaks may broaden, move, or even disappear after exchange experiments.
Does solvent polarity really matter?
Yes. Polar solvents can alter local shielding, stabilize hydrogen bonding, and shift exchangeable signals. The effect is often modest for fixed carbon sites but important for labile protons.
Why are 13C ranges wider than 1H ranges?
Carbon nuclei span a much larger chemical shift window because carbon environments differ more strongly in electron density and bonding patterns than most proton environments.
Does multiplicity change the chemical shift?
Multiplicity mainly affects splitting, not the core chemical shift. However, neighboring groups that cause splitting can also influence shielding through inductive and anisotropic effects.
Should I add every correction at once?
Only add meaningful corrections beyond the chosen base site. Overfilling options can double count effects and push predictions away from realistic values.
How should I compare this with a real spectrum?
Match the predicted region, not just one exact number. Then confirm with integration, multiplicity, carbon count, reference data, and the molecule’s expected functional groups.