What absorbs at 1245 cm⁻¹ in an FTIR spectrum?
A band near 1245 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 1245 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 |
|---|---|---|---|
| Acetate | 21 | 18 | 1.0 |
| Methacrylate | 20 | 17 | 1.0 |
| C-O single bond | 19 | 15 | 1.0 |
| Methoxy (OCH3) | 18 | 15 | 1.0 |
| Amide | 14 | 14 | 1.0 |
| Alkyl C-H | 9 | 8 | 1.0 |
| N h | 7 | 7 | 1.0 |
| Secondary amine | 6 | 6 | 1.0 |
| C n single bond | 6 | 6 | 1.0 |
| Carbohydrate | 5 | 5 | 1.0 |
| C c single bond | 5 | 5 | 1.0 |
| Ring structure | 4 | 4 | 1.0 |
| Carboxyl (COOH) | 4 | 4 | 1.0 |
| Carbonyl (C=O) | 4 | 4 | 1.0 |
| Ester | 4 | 3 | 1.0 |
| Aromatic ring | 4 | 3 | 1.0 |
| Hydroxyl (O-H) | 4 | 2 | 1.0 |
| Ketone | 2 | 2 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| Methyl | 1 | 1 | 1.0 |
| S eq o | 1 | 1 | 1.0 |
| Sulfate (SO4) | 1 | 1 | 1.0 |
| Hydrogen bond | 1 | 1 | 1.0 |
| C-S single bond | 1 | 1 | 1.0 |
| Protein | 1 | 1 | 1.0 |
| Acetyl | 1 | 1 | 1.0 |
| Bronsted acid site | 1 | 1 | 1.0 |
| Thiol | 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 |
|---|---|---|---|
| PVA | 1245, 1660, 2930 | Acetate, Methacrylate, C-O single bond | 1 |
| alginate | 1245, 1100, 1715 | Methacrylate, Acetate, Methoxy (OCH3) | 1 |
| rGO | 1245, 2358, 2930 | Methacrylate, Acetate, C-O single bond | 1 |
| polyaniline | 1245, 1565, 1570 | Methacrylate, Acetate | 1 |
| gold nanoparticles | 1245, 1638, 3252 | Methacrylate, Acetate | 1 |
| nanoparticles | 1245, 1732, 1647 | C-O single bond, 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 1245 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
“-OH stretching 2980-2920 stretching and bending vibrations of -CH Wavenumber (cm-1) Assignment 2061-1665 C-CH and O-CH stretch 1245”
Hydrating Capabilities of the Biopolymers Produced by the Marine Thermophilic Bacillus horneckiae SBP3 as Evaluated by ATR-FTIR Spectroscopy DOI: 10.3390/ma15175988 -
Alkyl C-H confidence 1.0
“C-H/N-H deformation) with small left-shifted variations at about 1245 A number of side-chain vibrations in the cm-1, 1310, 1390 and 1450 also known as non-specific or non-descriptive proteins, have appeared in spectra of skin cancers with a”
Eikje - 2011 - DNA-RNA, DNA-DNA, DNA-protein and protein-protein DOI: 10.1117/12.874692 -
Alkyl C-H confidence 1.0
“Raman cm-1 cm-1 band at 1245 is assigned to C-H stretching vibration of benzene ring.”
Jin 等 - 2018 - Polymer anode used in hydrometallurgy Anodic beha DOI: 10.1016/j.hydromet.2018.01.020 -
Alkyl C-H confidence 1.0
“Journal Pre-proof indicates a C=O stretch of carboxylic acid [6, 23] and IR spectrum of TSA conjugates showed a cm-1 -CH band at 1244.69 was the stretch of primary alcohol.”
Khalid 等 - 2020 - Thiolated sodium alginate conjugates for mucoadhes DOI: 10.1016/j.ijbiomac.2020.08.116 -
Acetate confidence 1.0
“[41-42] IR analysis of the whole plant extract of Gotu kola revealed that the presence of different functional groups ranging from O-H stretching, hydroxyl (3319.26 cm-1), C-H stretching, carbonyl (2921.96 cm-1), C=C stretching, aromatic ri”
Kumar 等 - 2021 - Centella asiatica mediated facile green synthesis DOI: 10.1016/j.inoche.2021.108865 -
Amide confidence 1.0
“cm-1 1211 C-O stretching vinyl ether C-O stretching vinyl ether cm-1 1245 Medium C-N stretching Medium C-N stretching”
Leemarose 等 - 2021 - Sustainable Synthesis of Gold Nanoparticles and it DOI: 10.13005/ojc/370216 -
Bronsted acid site confidence 1.0
“The increase in wavenum1500, 1576, and 1604 While both monodentate nitrates cm-1, ber of this peak at temperatures above 423 K can be interpreted s(NH 3) may be overlapping to form the peak at 1245 and (cid:228) as the desorption of NH from”
Pena 等 - 2004 - Identification of surface species on titania-suppo DOI: 10.1021/jp0313122 -
confidence 1.0
“As the aim of the analysis, the specific peak at 1245 among all of the states of PANI indicating the N-H stretching vibration was also reported in the spectra [35].”
Investigation of chemical bonding and electronic network of rGO/PANI/PVA electrospun nanofiber DOI: 10.1007/s00289-020-03442-7
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