What absorbs at 2005 cm⁻¹ in an FTIR spectrum?
A band near 2005 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 2005 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 |
|---|---|---|---|
| Alkyl C-H | 4 | 3 | 1.0 |
| Methacrylate | 4 | 3 | 1.0 |
| Acetate | 4 | 3 | 1.0 |
| Amide | 3 | 3 | 1.0 |
| Carbonyl (C=O) | 3 | 3 | 1.0 |
| Methoxy (OCH3) | 3 | 2 | 1.0 |
| C-O single bond | 3 | 2 | 1.0 |
| Ketone | 2 | 2 | 1.0 |
| Ester | 2 | 2 | 1.0 |
| Carboxyl (COOH) | 2 | 2 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| Siloxane (Si-O-Si) | 1 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Silicon hydride | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| Metal oxygen | 1 | 1 | 1.0 |
| N h | 1 | 0 | 1.0 |
Ranking reflects accumulated literature evidence, not a single authoritative rule. Always confirm against your sample context.
Possible materials
| Material | Supporting peaks | Overlapping groups | Cited sources |
|---|---|---|---|
| PEG | 2005, 1650, 1342 | Alkyl C-H, Methacrylate, Acetate | 1 |
| cellulose | 2005, 1735, 1650 | Alkyl C-H, Acetate, Methacrylate | 1 |
| lignin | 2005, 1035, 1510 | Alkyl C-H, Methacrylate, Acetate | 1 |
| hydrogel | 2005, 1632, 1062 | Amide, Methacrylate, Acetate | 1 |
| honey | 2005, 1199, 1345 | Methacrylate, Acetate, Alkyl C-H | 1 |
| gold nanoparticles | 2005, 1638, 3252 | Amide, Alkyl C-H, Methacrylate | 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 2005 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
-
Alkyl C-H confidence 1.0
“Thus the concentration of TPC in carbohydrate structure and characteristic of C H or C O honey is variable and depends on the geographical and stretching vibration (Tewari and Irudayaraj 2005).”
Physicochemical, antioxidant and FTIR-ATR spectroscopy evaluation of Kashmiri honeys as food quality traceability and Himalayan brand DOI: 10.1007/s13197-020-04878-5 -
Acetate confidence 1.0
“Further, a slight red-shift in the C=O stretching cm-1 Alexandridis 2005;”
Behera 和 Ram - 2013 - Synthesis and characterization of core-shell gold DOI: 10.1007/s13204-012-0076-x -
Carbonyl (C=O) confidence 1.0
“G-type lignin (Faix, 1991) Lignin 1269 Guaiacyl ring breathing with carbonyl stretching (Kubo and Kadla, 2005) Lignin 1030”
Dinant 等 - 2019 - Synchrotron FTIR and Raman spectroscopy provide un DOI: 10.1093/jxb/ery396 -
Hydroxyl (O-H) confidence 1.0
“to C=O stretching, C-N stretching, O-H bending and C-H evaluated by X-ray diffractometer, PANAlytical Model PW stretching vibrations, respectively (Can 2005;”
Mahmud 等 - 2018 - Influence of Poly (Ethylene Glycol) on the Charact DOI: 10.17576/jsm-2018-4706-14 -
Hydroxyl (O-H) confidence 1.0
“AppliedClayScience228(2022)106648 Si-O to the apical vibrations of apical bonds, in-plane Si-O-Si stretching vibrations, Si-O-Al vibrations, inner surface hydroxyl groups Al-O-H O-H vibrations in Al-O-H, respectively (Hoch vibrations and in”
Potential reactivity assessment of mechanically activated kaolin as alternative cement precursor DOI: 10.1016/j.clay.2022.106648 -
C-O single bond confidence 1.0
“et al., 1964) 2015) C-C (Labb´e p Pectin 1018 (Wilson et al., and C-O, 1504 et al., 2000) OCH vibration 2005) 1018 (McCann et al., 1500 (Sills and”
Unveiling the compositional remodelling of Arbutus unedo L. fruits during ripening DOI: 10.1016/j.scienta.2022.111248 -
Methoxy (OCH3) confidence 1.0
“2005) and methoxyl vibration (Moran et al.”
Chemical functional groups of extractives, cellulose and lignin extracted from native Leucaena leucocephala bark DOI: 10.1007/s00226-020-01258-2 -
Acetate confidence 1.0
“cm-1 1600 cm-1 was associated with the C=O stretching of proteins (Jabs 2005) or residual aceWhile the band at 1600 was associated with the C=O stretching of proteins (Jabs cm-1 tate, the low-intensity peak at 3000 cm-1 was associated with”
Minhas 等 - 2023 - Green Synthesis of Zinc Oxide Nanoparticles Using DOI: 10.3390/catal13030549
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