FTIR Spectrum Table
A complete infrared spectrum table covering 125 functional group absorption bands from 400 to 4000 cm⁻¹. Search by wavenumber or group name, filter by functional group category, and sort by frequency, intensity, or bond type. Built as a fast reference for students and researchers interpreting IR spectra. See the visual FTIR chart for a printable diagram, or explore guides on carbonyl peak identification, the fingerprint region, and how to read FTIR spectra.
125 entries400–4000 cm⁻¹8 categories
Quick Wavenumber Lookup
Enter a peak wavenumber from your spectrum to find matching functional groups.
cm⁻¹
FTIR Absorption Bands
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Range:–cm⁻¹
125 of 125 entries
O-H stretch (free)
Alcohols, Phenols3610–3670 cm⁻¹strongsharp
N-H stretch (1° amine, asymmetric)
Amines3350–3500 cm⁻¹mediumdoublet
N-H stretch (2° amine)
Amines3310–3500 cm⁻¹weaksharp
≡C-H stretch (terminal alkyne)
Alkynes3260–3330 cm⁻¹strongsharp
N-H stretch (1° amine, symmetric)
Amines3250–3400 cm⁻¹mediumdoublet
O-H stretch (hydrogen bonded)
Alcohols, Phenols3200–3550 cm⁻¹strongbroad
N-H stretch (amide)
Amides3180–3350 cm⁻¹mediumbroad
=C-H stretch (alkene)
Alkenes3020–3100 cm⁻¹mediumsharp
C-H stretch (aromatic)
Aromatics3000–3100 cm⁻¹mediumsharp
C-H stretch (CH₃ asymmetric)
Alkanes2950–2970 cm⁻¹strongsharp
C-H stretch (CH₂ asymmetric)
Alkanes2915–2940 cm⁻¹strongsharp
C-H stretch (CH₃ symmetric)
Alkanes2860–2885 cm⁻¹strongsharp
C-H stretch (CH₂ symmetric)
Alkanes2845–2870 cm⁻¹mediumsharp
C-H stretch (aldehyde, Fermi doublet high)
Aldehydes2820–2860 cm⁻¹mediumdoublet
C-H stretch (aldehyde, Fermi doublet low)
Aldehydes2700–2760 cm⁻¹mediumdoublet
NH₃⁺ stretch (amine salt/zwitterion)
Amine Salts2600–3100 cm⁻¹strongbroad
S-H stretch (thiol)
Thiols2550–2600 cm⁻¹weaksharp
O-H stretch (carboxylic acid)
Carboxylic Acids2500–3300 cm⁻¹strongbroad
O-H stretch (chelated enol)
Enols2500–3200 cm⁻¹variablebroad
CO₂ asymmetric stretch (atmospheric)
Atmospheric2310–2390 cm⁻¹strongdoublet
P-H stretch
Phosphorus Compounds2275–2440 cm⁻¹mediumsharp
Se-H stretch (selenol)
Selenium Compounds2260–2310 cm⁻¹weaksharp
N=C=O stretch (isocyanate)
Isocyanates2250–2275 cm⁻¹strongsharp
O-C≡N stretch (cyanate ester)
Cyanate Esters2240–2270 cm⁻¹strongsharp
C≡N stretch (nitrile)
Nitriles2210–2260 cm⁻¹strongsharp
C≡C stretch (internal alkyne)
Alkynes2190–2260 cm⁻¹weaksharp
C=C=O stretch (ketene)
Ketenes2140–2160 cm⁻¹strongsharp
S-C≡N stretch (thiocyanate)
Thiocyanates2140–2175 cm⁻¹strongsharp
N=C=N stretch (carbodiimide)
Carbodiimides2120–2145 cm⁻¹strongsharp
C≡C stretch (terminal alkyne)
Alkynes2100–2140 cm⁻¹weaksharp
Si-H stretch
Organosilicon2100–2250 cm⁻¹mediumsharp
N₃ asymmetric stretch (azide)
Azides2090–2160 cm⁻¹strongsharp
C=N₂ stretch (diazo)
Diazo Compounds2080–2110 cm⁻¹strongsharp
N=C=S stretch (isothiocyanate)
Isothiocyanates2050–2110 cm⁻¹strongsharp
C=C=N stretch (ketenimine)
Ketenimines1990–2020 cm⁻¹strongsharp
C=C=C stretch (allene)
Allenes1900–2000 cm⁻¹mediumsharp
C=O stretch (anhydride, symmetric)
Anhydrides1800–1850 cm⁻¹strongsharp
C=O stretch (acyl halide)
Acyl Halides1770–1815 cm⁻¹strongsharp
C=O stretch (β-lactam, 4-membered)
Lactams1760–1780 cm⁻¹strongsharp
C=O stretch (ester)
Esters1735–1750 cm⁻¹strongsharp
C=O stretch (lactone)
Lactones1735–1770 cm⁻¹strongsharp
C=O stretch (aldehyde)
Aldehydes1720–1740 cm⁻¹strongsharp
C=O stretch (anhydride, asymmetric)
Anhydrides1720–1775 cm⁻¹strongsharp
C=O stretch (carbonate)
Carbonates1720–1780 cm⁻¹strongsharp
C=O stretch (α,β-unsaturated ester)
Esters1715–1735 cm⁻¹strongsharp
C=O stretch (ketone)
Ketones1705–1725 cm⁻¹strongsharp
C=O stretch (carboxylic acid)
Carboxylic Acids1700–1725 cm⁻¹strongsharp
C=O stretch (γ-lactam, 5-membered)
Lactams1695–1715 cm⁻¹strongsharp
C=O stretch (carbamate/urethane)
Carbamates1690–1740 cm⁻¹strongsharp
C=O stretch (conjugated ketone)
Ketones1665–1700 cm⁻¹strongsharp
C=O stretch (δ-lactam, 6-membered)
Lactams1660–1680 cm⁻¹strongsharp
Aromatic overtone/combination bands
Aromatics1650–2000 cm⁻¹weakmultiple
C=O stretch (urea)
Ureas1640–1690 cm⁻¹strongsharp
C=O stretch (amide I)
Amides1630–1690 cm⁻¹strongsharp
C=O stretch (hydroxamic acid)
Hydroxamic Acids1630–1680 cm⁻¹strongsharp
C=C stretch (alkene)
Alkenes1620–1680 cm⁻¹variablesharp
C=N stretch (imine/oxime)
Imines1620–1690 cm⁻¹variablesharp
N-O stretch (organic nitrate, asymmetric)
Organic Nitrates1620–1660 cm⁻¹strongsharp
N=O stretch (organic nitrite)
Organic Nitrites1610–1680 cm⁻¹strongsharp
C=C stretch (aromatic, ~1600 cm⁻¹)
Aromatics1585–1615 cm⁻¹variablesharp
N-H bend (1° amine, scissors)
Amines1580–1650 cm⁻¹mediumsharp
H₂O bend (atmospheric water vapor)
Atmospheric1580–1650 cm⁻¹variablemultiple
COO⁻ stretch (carboxylate, asymmetric)
Carboxylate Salts1550–1610 cm⁻¹strongsharp
N-H bend (amide II)
Amides1510–1570 cm⁻¹strongsharp
NO₂ asymmetric stretch
Nitro Compounds1500–1570 cm⁻¹strongsharp
N=O stretch (nitroso, monomer)
Nitroso Compounds1500–1600 cm⁻¹strongsharp
C=C stretch (aromatic, ~1475 cm⁻¹)
Aromatics1450–1510 cm⁻¹variablesharp
C-H bend (CH₃ asymmetric deformation)
Alkanes1440–1465 cm⁻¹mediumsharp
C-H bend (CH₂ scissors)
Alkanes1440–1475 cm⁻¹mediumsharp
O-H bend (carboxylic acid)
Carboxylic Acids1395–1440 cm⁻¹mediumsharp
COO⁻ stretch (carboxylate, symmetric)
Carboxylate Salts1390–1420 cm⁻¹strongsharp
S=O stretch (sulfonyl chloride, asymmetric)
Sulfonyl Chlorides1380–1410 cm⁻¹strongsharp
S=O stretch (sulfate ester, asymmetric)
Sulfate Esters1380–1415 cm⁻¹strongsharp
C-H bend (CH₃ symmetric umbrella)
Alkanes1370–1390 cm⁻¹mediumsharp
S=O stretch (sulfonic acid, asymmetric)
Sulfonic Acids1342–1350 cm⁻¹strongsharp
S=O stretch (sulfonamide, asymmetric)
Sulfonamides1335–1370 cm⁻¹strongsharp
NO₂ symmetric stretch
Nitro Compounds1310–1370 cm⁻¹strongsharp
B-O stretch
Boronic Acids1310–1380 cm⁻¹strongsharp
S=O stretch (sulfone, asymmetric)
Sulfones1290–1350 cm⁻¹strongsharp
N-O stretch (organic nitrate, symmetric)
Organic Nitrates1255–1285 cm⁻¹strongsharp
C-N stretch (aromatic amine)
Amines1250–1360 cm⁻¹strongsharp
N→O stretch (aromatic N-oxide)
N-Oxides1250–1310 cm⁻¹strongsharp
Si-CH₃ deformation
Organosilicon1240–1280 cm⁻¹strongsharp
O-H bend (in-plane, alcohol)
Alcohols1230–1320 cm⁻¹mediumsharp
C-O stretch (epoxide ring)
Epoxides1230–1280 cm⁻¹strongsharp
C-O-C stretch (vinyl ether)
Ethers1200–1260 cm⁻¹strongsharp
S=O stretch (sulfate ester, symmetric)
Sulfate Esters1185–1200 cm⁻¹strongsharp
S=O stretch (sulfonyl chloride, symmetric)
Sulfonyl Chlorides1177–1204 cm⁻¹strongsharp
C-O stretch (phenol)
Phenols1170–1250 cm⁻¹strongsharp
S=O stretch (sulfonamide, symmetric)
Sulfonamides1155–1170 cm⁻¹strongsharp
C-O stretch (ester C-O-C)
Esters1150–1300 cm⁻¹strongsharp
P=O stretch
Phosphorus Compounds1150–1300 cm⁻¹strongsharp
S=O stretch (sulfonic acid, symmetric)
Sulfonic Acids1150–1165 cm⁻¹strongsharp
C-O stretch (3° alcohol)
Alcohols1125–1175 cm⁻¹strongsharp
S=O stretch (sulfone, symmetric)
Sulfones1120–1170 cm⁻¹strongsharp
C-O stretch (2° alcohol)
Alcohols1085–1125 cm⁻¹strongsharp
C-O-C stretch (ether)
Ethers1060–1150 cm⁻¹strongsharp
C=S stretch (thioamide/thione)
Thiocarbonyls1060–1200 cm⁻¹strongsharp
C-O stretch (1° alcohol)
Alcohols1040–1085 cm⁻¹strongsharp
S=O stretch (sulfoxide)
Sulfoxides1030–1070 cm⁻¹strongsharp
C-N stretch (aliphatic amine)
Amines1020–1250 cm⁻¹mediumsharp
C-F stretch
Haloalkanes1000–1400 cm⁻¹strongsharp
Si-O stretch
Organosilicon1000–1100 cm⁻¹strongbroad
Ring breathing (aromatic)
Aromatics990–1010 cm⁻¹variablesharp
P-O-C stretch (phosphate ester, asymmetric)
Phosphorus Compounds990–1050 cm⁻¹strongsharp
=C-H oop bend (trans alkene)
Alkenes960–975 cm⁻¹strongsharp
N→O stretch (aliphatic N-oxide)
N-Oxides950–970 cm⁻¹strongsharp
=C-H oop bend (vinyl/terminal)
Alkenes905–920 cm⁻¹strongsharp
=C-H oop bend (vinylidene)
Alkenes880–900 cm⁻¹strongsharp
C-H oop bend (1,4-disubstituted/para)
Aromatics800–860 cm⁻¹strongsharp
O-O stretch (peroxide)
Peroxides800–900 cm⁻¹weaksharp
C-H oop bend (1,3-disubstituted/meta)
Aromatics770–810 cm⁻¹strongsharp
P-O-C stretch (phosphate ester, symmetric)
Phosphorus Compounds740–830 cm⁻¹mediumsharp
C-H oop bend (1,2-disubstituted/ortho)
Aromatics735–770 cm⁻¹strongsharp
C-H oop bend (monosubstituted aromatic)
Aromatics730–770 cm⁻¹strongsharp
C-H rock (CH₂ rocking)
Alkanes715–740 cm⁻¹mediumsharp
N-H wag (2° amine)
Amines700–750 cm⁻¹weakbroad
Ring oop bend (monosubstituted aromatic)
Aromatics690–710 cm⁻¹strongsharp
Ring oop bend (1,3-disubstituted/meta)
Aromatics680–720 cm⁻¹strongsharp
=C-H oop bend (cis alkene)
Alkenes650–730 cm⁻¹mediumsharp
N-H wag (1° amine)
Amines650–900 cm⁻¹variablebroad
C-S stretch
Thioethers570–710 cm⁻¹weaksharp
C-Cl stretch
Haloalkanes550–800 cm⁻¹strongsharp
C-Br stretch
Haloalkanes500–680 cm⁻¹strongsharp
C-I stretch
Haloalkanes500–600 cm⁻¹strongsharp
How to Use This FTIR Spectrum Table
Follow these steps to identify functional groups from your infrared spectrum. Each absorption band in the table above corresponds to a specific molecular vibration — matching your observed peaks to these reference values is the core of FTIR spectrum interpretation.
- Start with the strongest, most distinctive peaks in your spectrum. Strong, isolated absorptions are the most reliable for identification.
- Check each wavenumber against the table — use the search box or category filters to narrow results. Look for entries whose wavenumber range brackets your observed peak position.
- Confirm with peak shape and intensity. A broad peak near 3300 cm⁻¹ suggests hydrogen-bonded O-H, while a sharp peak at the same position points to N-H.
- Look for corroborating peaks. Functional groups produce multiple absorptions — if you see C=O at 1720 cm⁻¹, check for O-H at 2500–3300 cm⁻¹ (carboxylic acid) or C-H at 2720 cm⁻¹ (aldehyde).
- Consider the full pattern, not just individual peaks. The fingerprint region (below 1500 cm⁻¹) is especially useful for confirming compound identity against reference spectra.
Understanding the Four Spectral Regions
| Region | Wavenumber Range | Key Bonds |
|---|---|---|
| X-H Stretching | 4000–2500 cm⁻¹ | O-H, N-H, C-H stretches |
| Triple Bond | 2500–2000 cm⁻¹ | C≡C, C≡N, cumulated C=C=C |
| Double Bond | 2000–1500 cm⁻¹ | C=O, C=C, C=N, aromatic ring |
| Fingerprint | 1500–400 cm⁻¹ | C-O, C-N, C-C stretches; bending modes |
Tips for Common Functional Groups
- Carbonyls — the C=O stretch (1650–1800 cm⁻¹) is the most reliable diagnostic peak in infrared spectroscopy. Its position narrows down the compound class.
- Alcohols — look for a broad O-H stretch (3200–3550 cm⁻¹) paired with a strong C-O stretch (1000–1260 cm⁻¹).
- Amines — primary amines show two N-H stretches (doublet near 3350–3500 cm⁻¹), secondary amines show one.
- Aromatics — look for C-H stretches just above 3000 cm⁻¹ and ring breathing modes near 1600–1450 cm⁻¹.
For a complete walkthrough, see the step-by-step FTIR interpretation guide.
Frequently Asked Questions
What are the main regions of an FTIR spectrum?
An FTIR spectrum is typically divided into four regions: the X-H stretching region (4000–2500 cm⁻¹) for O-H, N-H, and C-H bonds; the triple bond region (2500–2000 cm⁻¹) for C≡C and C≡N; the double bond region (2000–1500 cm⁻¹) for C=O, C=C, and C=N; and the fingerprint region (1500–400 cm⁻¹) containing complex bending and skeletal vibrations unique to each molecule.
How do I identify a carbonyl group in an FTIR spectrum?
The carbonyl (C=O) stretch appears as a strong, sharp absorption between 1650–1800 cm⁻¹. The exact position depends on the type: ketones near 1715 cm⁻¹, aldehydes near 1725 cm⁻¹, carboxylic acids near 1710 cm⁻¹, esters near 1735–1750 cm⁻¹, and amides near 1630–1680 cm⁻¹. This is one of the most diagnostic peaks in IR spectroscopy.
What is the fingerprint region in FTIR?
The fingerprint region (1500–400 cm⁻¹) contains complex absorption patterns from C-C, C-O, and C-N single bond stretches and various bending modes. This region is unique to each compound, like a fingerprint, making it valuable for compound identification by comparing against reference spectra.
How do I use an FTIR spectrum table to identify functional groups?
Start by noting the strongest peaks in your spectrum. Look up each peak’s wavenumber in the table to find matching functional groups. Confirm your assignment by checking that the peak shape (broad vs. sharp) and intensity (strong, medium, weak) match the expected pattern. Then look for corroborating peaks — for example, if you see a C=O stretch at 1710 cm⁻¹, check for a broad O-H near 2500–3300 cm⁻¹ to confirm a carboxylic acid.
What is the difference between FTIR and IR spectroscopy?
IR (infrared) spectroscopy is the broad technique of measuring how molecules absorb infrared light. FTIR (Fourier Transform Infrared) is the modern implementation that uses an interferometer and Fourier transform math to collect the entire spectrum at once, rather than scanning one wavelength at a time. Virtually all modern IR spectrometers are FTIR instruments, so the terms are often used interchangeably.
Why are some FTIR peaks broad and others sharp?
Peak shape reflects the bonding environment. Broad peaks usually indicate hydrogen bonding — the O-H stretch in alcohols (3200–3550 cm⁻¹) is broad because hydrogen bonds create a range of slightly different O-H bond strengths. Sharp peaks indicate a well-defined bond in a consistent environment, such as a free O-H or a C=O stretch. Doublets arise from symmetric and asymmetric stretching modes of groups like primary amines (two N-H bonds).
What wavenumber range does FTIR spectroscopy cover?
Standard FTIR instruments measure the mid-infrared region from 4000 to 400 cm⁻¹ (2.5–25 µm wavelength). This range captures the fundamental vibrations of most organic functional groups. Extended-range instruments can also measure the near-infrared (14,000–4000 cm⁻¹) and far-infrared (400–10 cm⁻¹) regions.