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IR Spectrum Simulator
Predict the infrared absorption spectrum of any organic molecule from its structure. Every band is labelled by the bond responsible for it — fully interpretable, no black box.
Free · No credit card
Quantum-chemistry-based predictions
Draw or import any molecule and the simulator predicts a transmittance spectrum with each absorption band labelled by the bond responsible for it. Predictions are based on a bond-environment database built from thousands of high-precision DFT calculations. Each bond is matched to the closest entry using graph-isomorphism on its local chemical environment — so every peak is traceable back to a specific part of your structure.
When to use it
- Structure verification — confirm a synthesised compound contains the expected functional groups before running expensive experiments
- Spectral assignment — match observed bands to specific bonds in a proposed structure, accelerating identification
- Comparison with experimental data — overlay simulated and measured spectra to quickly spot discrepancies that hint at structural errors
- Teaching — understand which bonds absorb at which frequencies and how the chemical environment influences band position and intensity
Example — Ethanol
For ethanol (CH₃CH₂OH), the simulator predicts the following characteristic absorptions:
- ~3300–3500 cm⁻¹ — broad O–H stretch (hydrogen-bonded hydroxyl)
- ~2900–3000 cm⁻¹ — C–H stretches (methyl and methylene)
- ~1450 cm⁻¹ — C–H bending (CH₂ and CH₃)
- ~1050–1100 cm⁻¹ — C–O stretch
Each band is annotated with the atom numbers of the contributing bond, so you can immediately relate a spectral feature to a specific part of your structure.