What absorbs at 989 cm⁻¹ in an FTIR spectrum?
A band near 989 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 989 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 |
|---|---|---|---|
| Methoxy (OCH3) | 4 | 4 | 1.0 |
| Methacrylate | 4 | 4 | 1.0 |
| C-O single bond | 4 | 4 | 1.0 |
| Acetate | 4 | 4 | 1.0 |
| Phosphate (PO4) | 3 | 3 | 1.0 |
| Hydroxyl (O-H) | 3 | 2 | 1.0 |
| Silicon-oxygen (Si-O) | 2 | 2 | 1.0 |
| Silicon (Si) | 2 | 2 | 1.0 |
| Nucleic acid | 2 | 2 | 1.0 |
| Lipid | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Protein | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Alkyl C-H | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 0.9 |
| Metal hydroxyl | 1 | 1 | 0.9 |
| Metal oxygen | 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 |
|---|---|---|---|
| PE | 989, 1414, 1700 | Methacrylate, Acetate, Methoxy (OCH3) | 1 |
| PP | 989, 1700, 1043 | Methacrylate, Acetate, Methoxy (OCH3) | 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 989 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
-
Acetate confidence 1.0
“The absorption band from 1,140 to 1,251 be attributed to the C-O-C 989cm-1 cm-1 stretching vibration and is the characteristic absorption vibration of PMMA, The band at 1,731 is the 1,445cm-1 representative of acrylate carboxyl group.”
Naik 等 - 2019 - Optical and Electrical Properties of TCNQ Doped PM DOI: 10.1063/1.5100466 -
Hydroxyl (O-H) confidence 1.0
“The band at 988.67 cm-1 suggests OH deformation linked to 2Al2;”
Foliar Application of Nanoclay Promotes Potato (Solanum tuberosum L.) Growth and Induces Systemic Resistance against Potato Virus Y DOI: 10.3390/v14102151 -
Acetate confidence 1.0
“Another band at 989 was assigned to a C-O-CH vibration of the ester group.”
Optical photothermal infrared spectroscopy with simultaneously acquired Raman spectroscopy for two-dimensional microplastic identification DOI: 10.1038/s41598-022-23318-2 -
Silicon (Si) confidence 1.0
“A study of fly ash cm-1 activation reports an intense band in 989 related to Si-O asymmetric stretching vibration, which explains that the lower wavenumber of this band was associated with a lower degree of crosslinking of the amorphous pha”
Concepcion Rodriguez-Robledo 等 - 2018 - Cellulose-Silica Nanocomposites of High Reinforcin DOI: 10.3390/ma11040575 -
Phosphate (PO4) confidence 1.0
“The bands at 989, cm-1 1083, and 1156 could be assigned to the asymmetric stretching vibration of P-O-P bonds linked with large met-”
Enhancement of structural and optical properties of transparent sodium zinc phosphate glass–ceramics nano composite DOI: 10.1007/s41779-022-00716-3 -
Nucleic acid confidence 1.0
“The bands at 989 1238 and 1091 were 42assigned to PO (nucleic acids), antisymmetric and symmetric stretching modes of 2-) phosphates (PO found in DNA (Barth et al., 1995;”
Le Roux 等 - 2015 - Fourier Transform Infrared spectroscopy discloses DOI: 10.1016/S0301-4622 -
Acetate confidence 1.0
“cm-1 stretch (1154-1155 It is worth noting that the band at 989 associated with C-O-H bending vibration at the C6 position, indicating the stretch of the interchain interaction via hydrogen bonding cm-1 for PUL, was found in the PUL powder”
Li 等 - 2017 - Electrospinning Pullulan Fibers from Salt Solution DOI: 10.3390/polym9010032 -
Protein confidence 1.0
“Across the PC1 versus PC2 scores plot, the untreated and washed isolates clustered together cm-1, cm-1, cm-1 cm-1, along PC1 due to loadings bands at 1634 1084 1047 and 989 which were along PC1 due to loadings bands at 1634 cm-1, 1084 cm-1,”
Influence of the Sample Preparation Method in Discriminating Candida spp. Using ATR-FTIR Spectroscopy DOI: 10.3390/molecules25071551
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