What absorbs at 2936 cm⁻¹ in an FTIR spectrum?
A band near 2936 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 2936 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 | 27 | 26 | 1.0 |
| Hydroxyl (O-H) | 6 | 6 | 1.0 |
| Methacrylate | 3 | 3 | 1.0 |
| Acetate | 3 | 3 | 1.0 |
| Methyl | 3 | 3 | 1.0 |
| Amide | 2 | 2 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| Ring structure | 2 | 2 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| Hydrogen bond | 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 |
| Lignin | 1 | 1 | 1.0 |
| Nucleic acid | 1 | 1 | 1.0 |
| Lipid | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Water (H2O) | 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 |
|---|---|---|---|
| TiO2 | 2936, 1700, 1093 | Hydroxyl (O-H), Alkyl C-H, Methacrylate | 1 |
| starch | 2936, 1650, 1540 | Hydroxyl (O-H), Methacrylate, Acetate | 1 |
| TiO2 nanoparticles | 2936, 1700, 455 | Hydroxyl (O-H), 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 2936 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
“The origin cm-1 of the vibration bands is as follows: at 3389 due to the NH stretching vibrations, cm-1 cm-1 at 2936 due to a CH-stretching vibrations, at 620 due to CH out-of-plane bending vibration.”
Synthesis and characterization thin films of conductive polymer (PANI) for optoelectronic device application DOI: 10.1063/1.4948838 -
Water (H2O) confidence 1.0
“The displayed weak absorption band at 2936 cm-1 suggested the asymmetric cm-1 water absorption [42].”
Lukova 等 - 2020 - Prebiotic Activity of Polyand Oligosaccharides O DOI: 10.3390/app10082648 -
Alkyl C-H confidence 1.0
“Stretching 3415, 1651 CH Asymmetric stretching 2936 3 CH”
Qin 等 - 2023 - Preparation and properties of silica solmelamine DOI: 10.1080/15685551.2022.2162280 -
Alkyl C-H confidence 1.0
“The peak at 2936 the ultimate tensile strength decreases at a 2.5% content corresponds to the C-H stretching whereas the peaks of chestnut husks and remains constant at 5% and 7.5%”
Preparation and characterization of a novel starch–chestnut husk biocomposite DOI: 10.1007/s42452-019-1204-y -
Alkyl C-H confidence 1.0
“The peaks of 2936 and 2832 were known as the stretching of asymmetric C-H alkanes [55] and PVP stretching of O-H, cm-1 were known as the stretching of asymmetric C-H alkanes [55] and PVP stretching respectively.”
TiO2 Nanoparticle Filler-Based Mixed-Matrix PES/CA Nanofiltration Membranes for Enhanced Desalination DOI: 10.3390/membranes11060433 -
Alkyl C-H confidence 1.0
“to the stretching vibration of the intramolecular hydrogen bond of the amino group of amide A, while cm-1 1036 are attributed to the characteristic vibrational modes of the pyranose ring [39], and the band the band observed around 2936 cm-1”
Preparation and Physicochemical Characterization of Softgels Cross-Linked with Cactus Mucilage Extracted from Cladodes of Opuntia Ficus-Indica DOI: 10.3390/molecules24142531 -
Alkyl C-H confidence 1.0
“stretching 2984 2 -CH Injection temperature (s) 20 3 3 -CH stretching 2936 Postinjection time (s) 10”
Cardenas-Trivino 等 - 2019 - Synthesis and Properties of Bionanocomposites of P DOI: 10.1155/2019/4520927 -
Alkyl C-H confidence 1.0
“In fact, in the presence of VeoVa, the ratio between larger number of CH groups in its side chain, the attribution of the band at ~2875 as 2 the intensities of the band at ~2875 cm-1 and the maximum band at 2936 cm-1 doubles: a spectral mar”
De Sa 等 - 2021 - Tracing Poly(Vinyl Acetate) Emulsions by Infrared DOI: 10.3390/polym13213609
Have a spectrum with this band?
Upload your FTIR spectrum and get a full interpretation report — peak assignments with literature citations, library matches, and a literature-backed analysis — in seconds.