This tool quickly identifies unknown peaks using a rich database of common functional groups and their signature absorption frequencies (in wavenumbers). Explore IR spectrum tables when you enter your data or download the full pdf version for instant reference. Try it now.
Infrared Frequency Lookup Tool
- Enter the wavenumber of interest in the box below
- Click "get
frequency groups" to view potential matches, expected peaks, intensity indications, and peak
assignment timing.
- Enter an IR absorption frequency (in cm⁻¹) to see common functional
groups associated with that region.
Enter a value between 3550 and 500 cm⁻¹. Results are based on general IR absorption tables and are not exhaustive.
Alkane
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 1350-1380 | Strong | δ(-(H)2C-H) |
| 1400-1470 | Medium | δ(-C-H) |
| 2800-3000 | Strong | ν(-C-H) |
Alkene
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 650-1000 | Medium | δ(=C-H) |
| 1640-1680 | Strong | ν(-C=C-) |
| 3000-3100 | Medium | ν(=C-H) |
Alkyne
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 610-700 | Medium | δ(≡C-H) |
| 2100-2260 | Weak | ν(-C≡C-) |
| 3270-3330 | Medium | ν(≡C-H) |
Aromatic
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 680-860 | Strong | δ(=C-H) |
| 1550-1700 | Medium | ν(-C=C-) |
| 3080-3020 | Variable | ν(=C-H) |
Alcohol
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 1087-1205 | Strong | ν(-C-OH) |
| 3200-3550 | Strong | ν(-(C)O-H) |
Phenol
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 680-860 | Strong | δ(C-H) |
| 1310-1390 | Strong | ν(C-OH) |
| 1550-1700 | Medium | ν(-C=C-) |
| 3200-3550 | Strong, Broad | ν(-(C)O-H) |
| 3330-3335 | Variable | ν(=C-H) |
Aldehyde/Ketone
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 1680-1750 | Strong | ν(-C=O) |
Ester
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 1163-1210 | Strong | ν(-C-O-) |
| 1735-1750 | Strong | ν(-C=O) |
Carboxylic Acid
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 910-950 | Medium | δ(-(C)O-H) |
| 1210-1320 | Medium | ν(-C-OH) |
| 1395-1440 | Medium | δ(-(C)O-H) |
| 1680-1760 | Strong | ν(-C=O) |
| 2500-3300 | Strong, Broad | ν(-(C)O-H) |
Carboxylic Acid Anhydride
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 1040-1050 | Strong, Broad | ν(-(O=)C-O-C(=O)-) |
| 1750-1820 | Strong | ν(-C=O) |
Primary Amine
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 660-900 | Medium | δ(-(C)-N-H) |
| 1020-1200 | Medium | ν(-C-N-) |
| 1500-1650 | Medium | δ(-(C)-N-H) |
| 3200-3500 | Medium, Two Bands | ν(-(C)-N-H) |
Secondary Amine
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 660-900 | Medium | δ(-(C)-N-H) |
| 1020-1200 | Medium | ν(-C-N-) |
| 3310-3350 | Medium | ν(-(C)-N-H) |
Tertiary Amine
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 1020-1200 | Medium | ν(-C-N-) |
Imine
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 2220-2260 | Weak | ν(-C=N-) |
Nitrile
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 2200-2300 | Medium | ν(-C≡N) |
Azide
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 2120-2160 | Strong | ν(-N=N=N) |
Oxyamine
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 1290-1370 | Strong | ν(-N-O-) |
| 1475-1550 | Strong | ν(-N-O-) |
Isocyanate
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 2250-2275 | Strong, Broad | ν(-N=C=O) |
Carbodiimide
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 2120-2145 | Strong | ν(-N=C=N-) |
Thiocyanate
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 2140-2175 | Strong | ν(-S-C≡N) |
Isothiocyanate
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 2140-2175 | Strong | ν(-N=C=S) |
Akyl Fluoride
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 1000-1400 | Strong | ν(-C-F) |
Alkyl Chloride
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 550-850 | Strong | ν(-C-Cl) |
Alkyl Bromide
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 515-690 | Strong | ν(-C-Br) |
Alkyl Iodide
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 500-600 | Strong | ν(-C-I) |
Thiol
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 2550-2600 | Weak | ν(-S-H) |
| 630-790 | Medium | ν(-C-S-) |
Sulfoxide
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 1030-1372 | Strong | ν(-S=O) |
Thioketone
| Expected Bands / cm-1 | Intensity/Width |
Assignment [δ = bend/ ν=stretch] |
| 1000-1250 | Weak | ν(-C=S) |
Please Note: This lookup is a quick reference guide. Always confirm assignments using complete IR tables, chemical context, and additional analytical techniques if needed.
This tool was created by one of our Former Application Scientists, Andrew. Please acknowledge Specac Ltd. and link to this web page if you use or reproduce it in any way.
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The same information is also available to download as a poster (see right).
