What absorbs at 2000 cm⁻¹ in an FTIR spectrum?
A band near 2000 cm⁻¹ can point to several functional groups. Below are the most likely assignments, ranked by how much published evidence supports each — every one traceable to literature (DOI) and cross-validated against our 130,000+ reference spectra and knowledge graph.
Backed by 8 cited sources
Quick answer
A band near 2000 cm⁻¹ is usually interpreted by checking which functional groups repeatedly co-occur there in the literature, then confirming at least one or two additional peaks in the same sample. This page ranks those assignments by accumulated evidence rather than by a single fixed textbook rule.
Possible functional-group assignments
| Functional group | Supporting facts | Cited sources | Top confidence |
|---|---|---|---|
| Silicon hydride | 11 | 7 | 1.0 |
| Alkyl C-H | 8 | 7 | 1.0 |
| Silicon (Si) | 7 | 6 | 1.0 |
| Amide | 6 | 5 | 1.0 |
| Methacrylate | 6 | 5 | 1.0 |
| Acetate | 6 | 5 | 1.0 |
| Methoxy (OCH3) | 5 | 4 | 1.0 |
| Adsorbed carbon monoxide | 5 | 3 | 1.0 |
| Hydroxyl (O-H) | 4 | 4 | 1.0 |
| Carbonyl (C=O) | 4 | 4 | 1.0 |
| C-O single bond | 4 | 3 | 1.0 |
| Alkene (C=C) | 3 | 3 | 1.0 |
| Silicon-oxygen (Si-O) | 3 | 3 | 1.0 |
| Hydrogen bond | 3 | 3 | 1.0 |
| Aromatic ring | 2 | 2 | 1.0 |
| Water (H2O) | 2 | 2 | 1.0 |
| Secondary amine | 2 | 2 | 1.0 |
| C n single bond | 2 | 2 | 1.0 |
| Silicon silicon | 2 | 2 | 1.0 |
| Siloxane (Si-O-Si) | 2 | 2 | 1.0 |
| Phosphate (PO4) | 2 | 2 | 1.0 |
| C c single bond | 2 | 2 | 1.0 |
| Methyl | 2 | 2 | 1.0 |
| N-O bond | 2 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Lipid | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Metal oxygen | 1 | 1 | 1.0 |
| Carbonate | 1 | 1 | 1.0 |
| Carbon dioxide | 1 | 1 | 1.0 |
| Borate | 1 | 1 | 1.0 |
| Silicate | 1 | 1 | 1.0 |
| C=n | 1 | 1 | 0.5 |
| Protein | 1 | 0 | 1.0 |
Ranking reflects accumulated literature evidence, not a single fixed rule. Always confirm against your sample context.
Possible materials
| Material | Supporting peaks | Overlapping groups | Cited sources |
|---|---|---|---|
| honey | 2000, 2005, 1199 | Alkyl C-H, Amide | 1 |
| apatite | 2000, 3053, 1640 | Amide, Alkyl C-H | 1 |
Materials are shown only when the same literature pool supports this band and at least one additional characteristic peak.
Spectrum logic
This band becomes meaningful only when read with its neighboring peaks. In practice, analysts first look at the assignments above, then check whether the same sample also shows other peaks expected for the same structural motif. A lone band near 2000 cm⁻¹ is usually not enough for material identification by itself.
Real-world usage
This type of query is common in polymer identification, unknown plastic screening, QC troubleshooting, recycled-material verification, and literature-backed peak assignment review.
Common mistakes
- Treating one isolated band as proof of a material without checking at least one or two supporting peaks.
- Ignoring overlap: multiple functional groups can contribute near the same wavenumber.
- Skipping validation when additives, blends, oxidation, or contamination may distort the spectrum.
Verification advice
When ambiguity remains, validate the hypothesis with DSC, GC-MS, or TGA, especially for blends, degraded samples, and filled polymers.
Literature behind these assignments
-
C c single bond confidence 1.0
“and a weak D peak near 1320 FTIR plot of DLC films shows a peak 1550 cm-1 corresponding to C-H stretching mode and peaks below 2000 near 2900 corresponding to C-C modes and C-H bending modes.”
DEPOSITION OF WIDE BAND GAP DLC FILMS USING R.F. PECVD AT VERY LOW POWER DOI: 10.1142/S0217979211100102 -
Carbonyl (C=O) confidence 1.0
“Strong absorption band at cm(cid:1)1 1742 is a sign of the stretching of the ester carbonyl 2000 C--O group and indication to the acetylation of starch [4].”
Microwave assisted acetylation of mung bean starch and the catalytic activity of potassium carbonate in freesolvent reaction DOI: 10.1002/star.201200081 -
Amide confidence 1.0
“The peak amounts (Gallardo-Velazquez, Osorio-Revilla, Loa, & 1547cm(cid:3)1 resulted from N-H bending and observed at Rivera-Espinoza, 2009) The band which varied between 1700cm(cid:3)1 C-N stretching vibrations of Amide II (Coates, 2000;”
Cebi 等 - 2020 - An evaluation of FTIR spectroscopy for prediction DOI: 10.1080/00218839.2019.1707009 -
Hydrogen bond confidence 1.0
“characteristically assigned to another form of bending The lowering of the frequency tends to be a function of the degree and strength of the hydrogen bonding vibration, the out-of-plane bend or wagging vibration of (Coates, 2000).”
Chik 等 - 2011 - Predicting group of metabolites available in parti DOI: 10.5897/AJB11.2736 -
Phosphate (PO4) confidence 1.0
“The bands at ~2000 are due to overtones of PO 4.”
Clark 等 - 2016 - Quantification of CO2 concentration in apatite DOI: 10.2138/am-2016-5661 -
Alkyl C-H confidence 1.0
“2011), and changes in the relative importance of lignin methoxyl groups for which the CH stretching 3 vibrations have lower CH stretching frequencies (Coates 2000).”
Esteves 等 - 2013 - CHEMICAL CHANGES OF HEAT TREATED PINE AND EUCALYPT DOI: 10.4067/S0718-221X2013005000020 -
confidence 1.0
“For example, cm-1 the peak at 2000 is a combination of Si-O-Si stretch-”
Han 和 Aydil - 1997 - Structure and chemical composition of fluorinated DOI: 10.1116/1.580845 -
Silicon (Si) confidence 1.0
“cm-1-2100 cm-1 3) the peak centered at 2000 due to the Si-H stretching modes;”
Hou 等 - 2011 - Evolution of infrared spectra and optical emission DOI: 10.1088/1674-1056/20/7/077802
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