What absorbs at 2902 cm⁻¹ in an FTIR spectrum?
A band near 2902 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 2902 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 | 13 | 13 | 1.0 |
| Carbohydrate | 2 | 2 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| Methyl | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| C-O single bond | 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 |
|---|---|---|---|
| PVA | 2902, 1660, 2930 | Alkyl C-H, Hydroxyl (O-H) | 1 |
| glycerol | 2902, 1585, 1630 | Alkyl C-H, Hydroxyl (O-H) | 1 |
| TiO2 | 2902, 1700, 1093 | Hydroxyl (O-H), Alkyl C-H | 1 |
| saliva | 2902, 1648, 1664 | Alkyl C-H, Carbohydrate | 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 2902 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
“C-H (aliphatic), and O-H are attributed to the bands at 1422, 1608, 2931, and 3420 cm-1 cm-1 cm-1 O-H stretching at 3458 and C-H stretching at 2902 are both absorption bands [26].”
Aziz 等 - 2022 - The Study of Ion Transport Parameters in MC-Based DOI: 10.3390/membranes12020139 -
Alkyl C-H confidence 1.0
“O-H stretching 3303 3305 3309 C-H stretching 2902”
Characteristics of a Plasticized PVA-Based Polymer Electrolyte Membrane and H+ Conductor for an Electrical Double-Layer Capacitor: Structural, Morphological, and Ion Transport Properties DOI: 10.3390/membranes -
Alkyl C-H confidence 1.0
“for the Cell-I is shifted to 2894 band at 2902 cm(cid:1)1 cm(cid:1)1 for the Cell-II structure at the shifted to 894 for the Cell-II, assigned as CH stretching in methylene22 NaOH concentration higher than 10.7 wt %, and it is at NaOH conce”
Characterization of chemically modified wood fibers using FTIR spectroscopy for biocomposites DOI: 10.1002/app.31746 -
C-O single bond confidence 1.0
“The symmetric and antisymmetric stretching modes of alcoholic -C-OH vibrations are obtained at 1401 2864 and 2902 cm-1”
Synthesis and characterization of cobalt ferrite nanoparticles for hyperthermia treatment application DOI: 10.1063/1.5052096 -
Alkyl C-H confidence 1.0
“Combined absorption of carboxylic -OH stretch and alcoholic -OH stretch Aliphatic -CH2 stretching 2902 Aliphatic -CH2 stretching 2900 Aliphatic -CH2 bending 1734”
Slightly carbomethylated cotton supported TiO2 nanoparticles as self-cleaning fabrics DOI: 10.1016/j.molcata.2014.11.012 -
Water (H2O) confidence 1.0
“Band assignment HS D-HS F-HS M-HS O-H stretching 3416-3244 3352 3479-3217 3460-3234 C-H stretching 2899 2906 2902 2912 water bending vibrations 1639 1639 1639 1639”
Bacterial nanocellulose from agro-industrial wastes: low-cost and enhanced production by Komagataeibacter saccharivorans MD1 DOI: 10.1038/s41598-020-60315-9 -
Alkyl C-H confidence 1.0
“The recorded FTIR spectrum shows characteristic bands of a cellulose structure, such as a peak located at 3401 cm-1 that corresponds to the stretching of the O-H groups and a peak at 2902 cm-1 due to C-H stretching [30].”
Application of a Low-Cost Cellulose-Based Bioadsorbent for the Effective Recovery of Terbium Ions from Aqueous Solutions DOI: 10.3390/met10121641 -
Alkyl C-H confidence 1.0
“cm-1 Stretching vibrations of CH and CH Phospholipids 2900 2 3 cm-1 CH symmetric stretch Lipids 2902 3”
Salivary ATR-FTIR Spectroscopy Coupled with Support Vector Machine Classification for Screening of Type 2 Diabetes Mellitus DOI: 10.3390/diagnostics13081396
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