What absorbs at 1431 cm⁻¹ in an FTIR spectrum?
A band near 1431 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 1431 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 | 6 | 6 | 1.0 |
| Acetate | 4 | 4 | 1.0 |
| Methacrylate | 3 | 3 | 1.0 |
| Hydroxyl (O-H) | 3 | 3 | 1.0 |
| C c single bond | 2 | 2 | 1.0 |
| Amide | 2 | 2 | 1.0 |
| Carbohydrate | 2 | 2 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| N-O bond | 2 | 2 | 1.0 |
| Water (H2O) | 2 | 2 | 1.0 |
| Ring structure | 2 | 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 |
| Hydrogen bond | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 1.0 |
| Lignin | 1 | 1 | 1.0 |
| Carbonate | 1 | 1 | 0.9 |
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 |
|---|---|---|---|
| Chitosan | 1431, 1650, 1655 | Alkyl C-H, Acetate, Methacrylate | 1 |
| Nanocellulose | 1431, 1540, 1646 | Alkyl C-H, Hydroxyl (O-H), Methacrylate | 1 |
| cellulose | 1431, 1735, 1650 | Alkyl C-H, Acetate, 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 1431 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
-
Water (H2O) confidence 1.0
“This was cm-1 found that trapped water molecules within the cellulose supported by characteristic peaks of lignin at 1431”
Extraction and Characterization of Nanocellulose from Raw Oil Palm Leaves (Elaeis guineensis) DOI: 10.1007/s13369-019-04131-y -
Acetate confidence 1.0
“The intensity of C-O vibration at 1431 of C0 was higher than 191 that of C1, C3 and C5.”
Investigating the effect of carbon nanotube on early age hydration of cementitious composites with isothermal calorimetry and Fourier transform infrared spectroscopy DOI: 10.1016/j.cemconcomp.2020.103513 -
Alkyl C-H confidence 1.0
“LLM confirmed rule peak-group candidate”
Mahardiani 等 - 2022 - Nanofiber Fabrication from Palm Fiber Waste for Su DOI: 10.48317/IMIST.PRSM/morjchem-v10i2.32648 -
Water (H2O) confidence 1.0
“related to some suggested polymerization of the phosphate network and formation of pyrophosphate units cm-1) with vibrations at (1384 and the high response cm-1 cm-1 (i) The first far-IR band with peaks at 460 and 545 of a new band 1431 whi”
Photoluminescence, optical and structural properties of Pr3+-doped fluorophosphate glasses and their induced defects by gamma irradiation DOI: 10.1007/s10854-018-9120-2 -
Acetate confidence 1.0
“2 the gel was heated up to 400 (cid:1)C the acetate peaks decreased in intensity, and evidence of carbonate groups (C@O cm(cid:2)1 appeared, as signified by the peaks at 1431 4.”
Tangwiwat 和 Milne - 2005 - Barium titanate sols prepared by a diol-based sol- DOI: 10.1016/j.jnoncrysol.2004.12.008 -
Alkyl C-H confidence 1.0
“Both bands cm-1 cm-1 at 1431 and 1483 reflected the stretching of C-H groups, while the band at cm-1 1740 showed the stretching of C=O carboxylic groups, confirming the presence of cm-1, cm-1, polycarboxylate in BioRoot.”
Assiry 等 - 2023 - Microstructural and Elemental Characterization of DOI: 10.3390/app13074517 -
Alkyl C-H confidence 1.0
“• Vibrations of-OH groups from PEG and CHI are evidenced by the peak at around 1431 cm-1 corresponding to δCH2 in CH2OH groups.”
Caprarescu 等 - 2020 - Biopolymeric Membrane Enriched with Chitosan and S DOI: 10.3390/polym12081792 -
Hydroxyl (O-H) confidence 1.0
“The three peaks are coracteristic absorption peak of telescopic vibration of O-H, responding to three different chemical environcm-1 and the 1431 is the characteristic absorption peak of 29Si ments of Si on POSS-triol.”
Chen 等 - 2019 - Preparation of POSS-triolwollastonite composite p DOI: 10.1515/secm-2019-0001
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