# NMR / IR Spectroscopy Peak Predictor

Predict characteristic ¹H / ¹³C NMR shifts and IR bands from the functional groups you select — annotated simulated spectrum, carbonyl discrimination table, every peak explained.

> Canonical page: https://elysiatools.com/en/tools/nmr-ir-peak-predictor

- **Category:** Science & Education

- **Keywords:** nmr predictor, ir spectrum predictor, chemical shift table, functional group identification, organic chemistry spectroscopy

## Overview

Additive textbook model (ChemDraw ChemNMR's approach): the predicted spectrum is the union of the selected groups' characteristic band sets, each with range, intensity, shape, diagnostic weight and a physical cause. Carbonyl ordering (acyl chloride > anhydride > ester > aldehyde > ketone > acid > amide) is the discrimination core; conjugation subtracts 20–40 cm⁻¹. Aromatic substitution patterns map to 690–900 cm⁻¹ oop bands (mono 690+750, ortho ~750, meta 690+780+880, para 800–850). ¹H ranges run 0.9–13.2 ppm with exchangeable-proton flags; ¹³C covers 0–220 ppm. Includes n+1 rule, Pascal intensities and coupling constants (alkene trans 12–18 vs cis 6–14 Hz). Educational accuracy, not quantum chemistry.

## Inputs

- **Functional groups (one per line)** (textarea): ester aromatic ring ketone
- **Apply conjugation shift to carbonyls** (checkbox)
- **Aromatic substitution pattern** (select)
- **Show IR spectrum panel** (checkbox)
- **Show ¹H NMR panel** (checkbox)
- **Show ¹³C NMR panel** (checkbox)

## When to use

- Predicting expected spectral peaks and chemical shift windows before analyzing laboratory NMR and IR data.
- Distinguishing between similar carbonyl-containing functional groups such as esters, ketones, and amides.
- Studying or teaching organic spectroscopy concepts, including aromatic substitution patterns, conjugation shifts, and n+1 spin-spin coupling.

## How it works

- Enter one or more functional groups into the input box, one per line (such as ester, aromatic ring, or ketone).
- Set structural modifiers by checking carbonyl conjugation and selecting an aromatic substitution pattern (mono, ortho, meta, or para).
- Toggle visibility for IR, ¹H NMR, and ¹³C NMR panels to view simulated spectra, peak ladders, and underlying physical explanations.

## Use cases

- Verifying whether an unknown sample's IR carbonyl stretch matches an ester, aldehyde, or conjugated ketone.
- Estimating ¹H and ¹³C NMR shift regions to assign peaks in synthetic reaction product spectra.
- Preparing annotated spectroscopy diagrams and educational reference tables for chemistry coursework.

## Frequently asked questions

### Is this tool running quantum chemical calculations?

No. It uses a textbook additive increment model based on empirical reference ranges from standard chemical literature.

### How does the conjugation option change the results?

Enabling conjugation subtracts 20–40 cm⁻¹ from carbonyl IR stretching frequencies to reflect resonance delocalization.

### What aromatic substitution patterns are supported in IR?

The predictor models out-of-plane C–H bending between 690–900 cm⁻¹ for monosubstituted, ortho (1,2), meta (1,3), and para (1,4) rings.

### Are exchangeable protons indicated in the ¹H NMR panel?

Yes. Labile protons on hydroxyl (–OH) and amine (–NH) groups are flagged with broad peak notations and D₂O exchange sensitivity.

### Can I hide spectrum panels I do not need?

Yes. Use the showIR, show1H, and show13C checkboxes to display only the spectral techniques relevant to your analysis.

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