What absorbs at 2857 cm⁻¹ in an FTIR spectrum?
A band near 2857 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 2857 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 | 16 | 15 | 1.0 |
| Methacrylate | 3 | 3 | 1.0 |
| Carbonyl (C=O) | 3 | 3 | 1.0 |
| Amide | 3 | 3 | 1.0 |
| Acetate | 3 | 3 | 1.0 |
| Ketone | 2 | 2 | 1.0 |
| Ester | 2 | 2 | 1.0 |
| Carboxyl (COOH) | 2 | 2 | 1.0 |
| Secondary amine | 2 | 2 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Fatty acid | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Hydrogen bond | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| C n 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 |
|---|---|---|---|
| ZnO | 2857, 1400, 3430 | Alkyl C-H, Methacrylate, Amide | 2 |
| ZnO nanoparticles | 2857, 1219, 1726 | Alkyl C-H, Methacrylate, Amide | 1 |
| cellulose | 2857, 1735, 1650 | Alkyl C-H, Methacrylate, Amide | 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 2857 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
“They observed vibrations of C-H functional groups at 2856.67 cm-1 and 2926.11 cm-1.”
The Effect of High-Intensity Ultrasound and Natural Oils on the Extraction and Antioxidant Activity of Lycopene from Tomato (Solanum lycopersicum) Waste DOI: 10.3390/antiox11071404 -
Alkyl C-H confidence 1.0
“The absorption bands at 2927, 2934, 2857, and are due to the stretching vibration of CH groups.”
Innovative Investigation of Zinc Oxide Nanoparticles Used in Dentistry DOI: 10.3390/cryst12081063 -
Alkyl C-H confidence 1.0
“3 cm-1, 4716 8709 symmetric stretching vibration at 2876 the cm-1, CH symmetric stretching vibration at 2857 4777 9181 2 COOcm-1 the symmetric stretch band at 1391 and”
Wang 等 - 2012 - Differentiation in MALDI-TOF MS and FTIR spectra b DOI: 10.1186/1471-2180-12-182 -
confidence 1.0
“It exhibits a relatively broad peak at about 3306 cm-1 attributed to the N-H stretching vibrations (with NH involved in hydrogen bonding) and two other absorption bands around 2930 and 2857 cm-1 assigned to the asymmetric and symmetric C-H”
Evaluation of Water Sorption and Solubility and FTIR Spectroscopy of Thermoplastic Orthodontic Retainer Materials Subjected to Thermoforming and Thermocycling DOI: 10.3390/app13085165 -
Carbohydrate confidence 1.0
“cm-1 al.[31] in the FTIR spectra of all samples, which according to Rosa et is assigned to C = O 1734 2857cm-1 in the spectrum of ketone due to hemicelluloses.”
Alghooneh 等 - 2017 - Characterisation of cellulose from coffee silversk DOI: 10.1080/10942912.2016.1253097 -
Alkyl C-H confidence 1.0
“Spectrum of the PE film before irradiation show the 05 characteristic absorption peaks of long alkyl chain in the 2919cm-1, 2857cm-1, 1475cm-1, 715cm-1.”
Asghar 等 - 2011 - Comparative Solid Phase Photocatalytic Degradation DOI: 10.1155/2011/461930 -
Alkyl C-H confidence 1.0
“As shown in Figure S4 (zoomed part), prominent cm-1 cm-1 O-H 1250 can be attributed to stretching, while bands are because of stretching bands at 1576, 1607, and 1628 cm-1 C-H are due to the stretching of at 2857 and 2924 vibrations of the”
Bir 等 - 2022 - Multifunctional Ternary NLPZnO@L-cysteine-grafted DOI: 10.1021/acsomega.2c04936 -
Alkyl C-H confidence 1.0
“2857 cm-1 attributed to the MZ1 MZ1 MZ2 MZ2 CH of the alkane chain.”
Effect of the Zwitterion, p(MAO-DMPA), on the Internal Structure, Fouling Characteristics, and Dye Rejection Mechanism of PVDF Membranes DOI: 10.3390/membranes10110323
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