What absorbs at 1128 cm⁻¹ in an FTIR spectrum?
A band near 1128 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 1128 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 |
|---|---|---|---|
| C-O single bond | 7 | 5 | 1.0 |
| Methoxy (OCH3) | 5 | 4 | 1.0 |
| Methacrylate | 5 | 4 | 1.0 |
| Acetate | 5 | 4 | 1.0 |
| Alkyl C-H | 4 | 4 | 1.0 |
| Secondary amine | 2 | 2 | 1.0 |
| C n single bond | 2 | 2 | 1.0 |
| Amide | 2 | 2 | 1.0 |
| Silicon carbon | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Methyl | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
| Metal oxygen | 1 | 1 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 0.8 |
| Carboxyl (COOH) | 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 |
|---|---|---|---|
| PLA | 1128, 1650, 1073 | Methacrylate, Acetate, Methoxy (OCH3) | 1 |
| TiO2 | 1128, 1700, 1093 | Methacrylate, Acetate, C-O single bond | 1 |
| CS | 1128, 1645, 1720 | Methacrylate, C-O single bond, 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 1128 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 FTIR spectroscopy study of neat PLA having various functional groups C=O al cm-1), cm-1), stretching vibrations (~ 1749 asymmetric C-O-C stretching (1180 symmetric and cm-1), cm-1), asymmetric -CH vibrations (1128 and 1042 C-OH side gro”
Ghosh 等 - 2020 - Blown films fabrication of poly lactic acid based DOI: 10.1016/j.mtcomm.2019.100737 -
Acetate confidence 1.0
“The peak at 1128 cm-1 was associated to the stretching of the C-O A white oak barrel was purchased from artisan”
Mondragon-Cortez 等 - 2022 - Application of Fourier transform infrared spectros DOI: 10.24275/rmiq/Alim2806 -
confidence 1.0
“1043cm(cid:2)1 ance of peaks at 1128, 1080, and may correspond to 2 (degrees) CAO stretching vibrations (Pamula et al., 2001).”
Molinaro 等 - 2013 - Effect of nanoclay-type and PLA optical purity on DOI: 10.1016/j.jfoodeng.2013.01.021 -
Metal oxygen confidence 1.0
“1039 correspond to the vibrations of the Ti-O-C of the butoxy groups bonded directly to the cm-1 cm-1) Interestingly, these bands (1128 and 1039 present a significant variation in their intensity ratios cm-1 when both systems are compared.”
Synthesis of vacancy-rich titania particles suitable for the additive manufacturing of ceramics DOI: 10.1038/s41598-022-19824-y -
Acetate confidence 1.0
“The bands at 1128 and 1170 are attributed to C-O and C-OH bending vibration and determine the proportion of the crystalline phase [48].”
High-Content Aloe vera Based Hydrogels: Physicochemical and Pharmaceutical Properties DOI: 10.3390/polym15051312 -
Acetate confidence 1.0
“cm-1 The vibration at 1128 from PVA is ascribed to the stretching of C-O from the crystalline The vibration at 1128 cm-1 from PVA is ascribed to the stretching of C-O from the crystalline region of the macromolecular chain where hydrogen bo”
Croitoru 等 - 2020 - Physically Crosslinked Poly (Vinyl Alcohol)Kappa- DOI: 10.3390/polym12030560 -
Acetate confidence 1.0
“3 cm-1, cm-1, 1454-1456 cm-1, CH3 rocking vibration assigned to 1128 cm-1, C-O-C stretching assigned to 1095-1098 vibration at 1454-1456 CH rocking vibration assigned to 1128 C-O-C stretching assigned 3 cm-1, cm-1,”
Impact of the Fused Deposition (FDM) Printing Process on Polylactic Acid (PLA) Chemistry and Structure DOI: 10.3390/app7060579 -
Amide confidence 1.0
“cm-1, (-2291.54eV), (-10569.73 molecule electronic energy vibration at 1372 N-O symmetric stretch at 1289 cm-1, cm-1 eV), core-core repulsion energy (8278.19eV), cosmo C-N stretch at 1128 and C-O stretch at”
Experimental and computational chemistry studies on the inhibition of aluminium and mild steel in 0. DOI: 10.1080/16583655.2018.1500514
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