What absorbs at 2847 cm⁻¹ in an FTIR spectrum?
A band near 2847 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 2847 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 | 18 | 16 | 1.0 |
| Methacrylate | 3 | 3 | 1.0 |
| Amide | 3 | 3 | 1.0 |
| Acetate | 3 | 3 | 1.0 |
| Carboxyl (COOH) | 3 | 3 | 1.0 |
| Hydrogen bond | 2 | 2 | 1.0 |
| Ketone | 2 | 2 | 1.0 |
| Ester | 2 | 2 | 1.0 |
| Carbonyl (C=O) | 2 | 2 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| Hydroxyl (O-H) | 2 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Ammonium | 1 | 1 | 1.0 |
| Water (H2O) | 1 | 0 | 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 |
|---|---|---|---|
| LDPE | 2847, 1720, 1737 | Alkyl C-H, Methacrylate, Acetate | 2 |
| chitosan | 2847, 1650, 1655 | Alkyl C-H, Amide, Acetate | 1 |
| gelatin | 2847, 1652, 3300 | Amide, Methacrylate, Acetate | 1 |
| polystyrene | 2847, 1020, 1600 | Alkyl C-H, Methacrylate, Acetate | 1 |
| PMMA | 2847, 1722, 1383 | Methacrylate, Acetate, Alkyl C-H | 1 |
| lignin | 2847, 1035, 1510 | Alkyl C-H, Methacrylate, Acetate | 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 2847 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
-
Carboxyl (COOH) confidence 1.0
“The peak at 2935 cm-1 (Figure 3) can be ascribed to -CH cm-1 shifts to 2943 in the doped PMMA sample (Figure 3) and a new peak at 2847 appeared, which is stretching and shifts to 2943 in the doped PMMA sample (Figure 3) and a new peak at 28”
Aziz 等 - 2017 - From Insulating PMMA Polymer to Conjugated Double DOI: 10.3390/polym9110626 -
Ammonium confidence 1.0
“The analysis of structural changes conducted by XRD analysis showed the peak shifting from cm-1 19.89° to 16.1° and specific peak spectra FTIR of 2846.93 due to increase basal spacing from ammonium intercalation.”
Hakim 等 - 2023 - Ammonium-Assisted Intercalation of Java Bentonite DOI: 10.12911/22998993/156665 -
Alkyl C-H confidence 1.0
“These compounds improve MP-PS stretching of the other C-H groups is detected at 2847 cm-1.”
Optimization of Polystyrene Biodegradation by Bacillus cereus and Pseudomonas alcaligenes Using Full Factorial Design DOI: 10.3390/polym14204299 -
Alkyl C-H confidence 1.0
“Structural Changes of Polyethylene by Fourier Transform Infrared (FTIR) Analysis stretching (1461 cm-1), C-H stretching symmetrically (2847 cm-1), and C-H stretching symWhen comparing treated LDPE to control samples, FTIR revealed both the”
Isolation and Characterization of Brucella spp., Low-Density Polyethylene (LDPE) Plastic Degrading Bacteria in Al-Ahsa Region, Saudi Arabia DOI: 10.3390/app13074629 -
Amide confidence 1.0
“2914 2914 2922 2922 2929 CH antisymmetric and symmetric stretching Amide B 2847 2847 2847 2840 2876 CH antisymmetric and symmetric stretching COOC=O Amide I 1738 1745 1656 1656 1648 stretch/hydrogen bond coupled 1603 1595 1544 1544 1551 NH”
Characterization of gelatin/chitosan ploymer films integrated with docosahexaenoic acids fabricated by different methods DOI: 10.1038/s41598-019-44807-x -
Acetate confidence 1.0
“In addition, characteristic bands of 1732cm-1, beeswax are observed: C=O stretching vibrations at sharp C-H stretching vibration bands at 2847cm-1 2915 and and sharp combination bands of CH stretching and bending of aliphatic chains at 4343”
Daher 等 - 2019 - Spectroscopic characterization of selected French DOI: 10.1080/03087298.2003.10441266. -
Alkyl C-H confidence 1.0
“During the co-culture growth of CPEF-6 with T-LDPE, 3614 cm-1 (-O-H stretching) (Figure 7B), 2914 cm-1 (-CH asymmetric stretching) (Figure we detected the production of laccase, and the activity of laccase gradually increased and 7C), 2847”
Gong 等 - 2023 - Biodegradation of Low Density Polyethylene by the DOI: 10.3390/jof9060605 -
Aromatic ring confidence 1.0
“Whereas the bands at 2936 and 2847 cm-1 stretching vibrations in aromatic and aliphatic O-H groups.”
Guo 等 - 2020 - The Influence of Compatibility on the Structure an DOI: 10.3390/polym12010056
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