What absorbs at 1997 cm⁻¹ in an FTIR spectrum?
A band near 1997 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 1997 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 | 4 | 1.0 |
| Aromatic ring | 2 | 2 | 1.0 |
| Hydroxyl (O-H) | 2 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Carbonate | 1 | 1 | 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 |
|---|---|---|---|
| cotton | 1997, 1030, 1638 | Alkyl C-H, Hydroxyl (O-H), Carbohydrate | 1 |
| quartz | 1997, 800, 3053 | Hydroxyl (O-H), Alkyl C-H | 1 |
| apatite | 1997, 3053, 1640 | Hydroxyl (O-H), 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 1997 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
-
Hydroxyl (O-H) confidence 1.0
“Although cell elongation is deficiency significantly affects the position and intenceased by B deficiency, the rapid cell division does sity of carboxylic bands (Figure 3(b)), and the denot stop and cell wall synthesis continues, ultimately”
Changes in chemical composition and structure of root cell wall of citrus rootstock seedlings in response to boron deficiency by FTIR spectroscopy DOI: 10.1080/14620316.2017.1362327 -
Carbonate confidence 1.0
“cm(cid:3)1 CO235 1651 physisorbed were observed and characterized for adsorbed CO2 and and a peak at 1735 due to carboxylate (CO32(cid:3) cm(cid:3)1 (COOe species.34 ).36 carbonate species ) The peak at 1997 may be due to For Ce0.5ZSM-5 cat”
CO oxidation and 4-nitrophenol reduction over ceria-promoted platinum nanoparticles impregnated with ZSM-5 zeolite DOI: 10.1016/j.jre.2021.07.009 -
Alkyl C-H confidence 1.0
“The protein-to-lipid ratio was also calculated by taking symmetric stretching band at which arises from P-O stretching, for Micrococcus species (Stuart, the ratio of the area of the CH 3 2876cm(cid:2)1 to the area of the CH asymmetric stret”
Use of Fourier transform infrared spectroscopy for rapid comparative analysis of Bacillus and Micrococcus isolates DOI: 10.1016/j.foodchem.2008.08.063 -
Alkyl C-H confidence 1.0
“The frequency range of and the out-of-plane bending vibration of cm(cid:1)1 cm(cid:1)1 3009-2800 is due to CH stretching absorptions, (Guillen & Cabo, 1997b).”
Syahariza 等 - 2005 - Detection of lard adulteration in cake formulation DOI: 10.1016/j.foodchem.2004.10.039 -
Carbonyl (C=O) confidence 1.0
“Peaks at 1696 correspond to the benzoyl carbonyl stretch cm-1 and those at 1721 and 1724 correspond to the acid carbonyl stretch (Taylor and A Zografi, 1997).”
Bandi 等 - 2004 - Preparation of budesonideand indomethacin-hydrox DOI: 10.1016/j.ejps.2004.06.007. -
Alkyl C-H confidence 1.0
“Deo & Natarajan, 1997 Absorbance bands 300 - 600 CH Rocking vibrations Deo & Natarajan, 1997 and the characteristic functional groups.”
Merma 等 - 2017 - DOI: 10.1590/0370-446720167000063 -
Aromatic ring confidence 1.0
“In this context, the heterogeneity of the cm-1, aromatic ring stretching) (Agarwal and Ralph 1997).”
Pedersen 等 - 2015 - Bacterial and abiotic decay in waterlogged archaeo DOI: 10.3929/ethz-b-000095042 -
Alkyl C-H confidence 0.9
“Text: 'peaks at 1997 and 1969 cm-1 indicate bending of the CH bond, i.e., the presence of aromatic groups'”
Grgac 等 - 2022 - The Effect of Ultrasonic Treatment on the Binding DOI: 10.3390/ma15020470
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