What absorbs at 978 cm⁻¹ in an FTIR spectrum?
A band near 978 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 978 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 |
|---|---|---|---|
| Silicon-oxygen (Si-O) | 3 | 3 | 1.0 |
| Silicon (Si) | 3 | 3 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| Phosphate (PO4) | 2 | 2 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| Siloxane (Si-O-Si) | 2 | 2 | 1.0 |
| Amide | 2 | 2 | 1.0 |
| Alkyl C-H | 2 | 2 | 1.0 |
| C c single bond | 2 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Phosphorus | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Silicon hydride | 1 | 1 | 1.0 |
| Borate | 1 | 1 | 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 |
|---|---|---|---|
| saliva | 978, 1648, 1664 | Methacrylate, Methoxy (OCH3) | 1 |
| PHB | 978, 3440, 1724 | Methacrylate, Methoxy (OCH3) | 1 |
| PLLA | 978, 1182, 921 | Methoxy (OCH3), 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 978 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
“related to the PLLA crystal [19], the crystalline band It shows decreasing of the glass transition temperatures cm-1 at 978 is given to bending vibrations of -C-H (Tg)inthePLLA,PDLLAandPHBblendswithanadditive.”
El-Hadi - 2019 - Miscibility of CrystallineAmorphousCrystalline B DOI: 10.1080/03602559.2018.1455863 -
Borate confidence 1.0
“2) could 4(cid:2) unit-related B-O stretching correspond to BO 978-cm(cid:2)1 IR band indicates the vibrations.”
Lakshminarayana 等 - 2019 - Borotellurite Glasses for Gamma-Ray Shielding An DOI: 10.1007/s11664-018-6810-8 -
Hydroxyl (O-H) confidence 1.0
“cm-1 amide I and II may be substituted at 1643.1 The peak at 978.3 is associated with alcohol and amine stretching vibrations.”
Synthesis and Characterization of Sulfur Nanoparticles of Citrus limon Extract Embedded in Nanohydrogel Formulation: In Vitro and In Vivo Studies DOI: 10.3390/gels9040284 -
Amide confidence 1.0
“of the protein β-sheet (978 cm-1), and the band of Amide III (centered at 1255 cm-1).”
The Role of the Preanalytical Step for Human Saliva Analysis via Vibrational Spectroscopy DOI: 10.3390/metabo13030393 -
Silicon hydride confidence 1.0
“In the curve of paring curves b and c, it could be found that the cm-1 824 belonged to the symmetric deformation vibration of the four-membered ring in appeared in the infrared spectrum of the prepolymer appeared, which further proved that”
Chen 等 - 2021 - Synthesis of a novel UV-curable prepolymer 1,3-bis DOI: 10.2478/msp-2021-0030 -
Aromatic ring confidence 1.0
“1165 other scissoring mode vibrations were assigned at 1172, 1118, and 1093 cm-1 The C-H out-of-plane bending (twisting vibrations) was observed at 978 and calcm-1, culated at 984 a series of twisting vibrations bands were found at 970, 940”
Density Functional Theory and Molecular Docking Investigations of the Chemical and Antibacterial Activities for 1-(4-Hydroxyphenyl)-3-phenylprop-2-en-1-one DOI: 10.3390/molecules26123631 -
Phosphate (PO4) confidence 1.0
“The (cid:2872)(cid:2871)(cid:2879) PO P-O vibration asymmetry of in the cement was attributable to the adsorption bands PO3- (cid:2872)(cid:2871)(cid:2879) The P-O vibration asymmetry of in the cement was attributable to the adsorption PO P”
Synthesis and Characterization of New Composite Materials Based on Magnesium Phosphate Cement for Fluoride Retention DOI: 10.3390/ma16020718 -
Amide confidence 1.0
“The matic ring stretching and sharp peaks at 1392 and 1064 cm-1 C-N broad peaks indicate presence of oxygen spaces and local correspond to stretching vibrations of aliphatic 978cm-1 lattice disorder in sample [38].”
Green Synthesized Phytochemically (Zingiber officinale and Allium sativum) Reduced Nickel Oxide Nanoparticles Confirmed Bactericidal and Catalytic Potential DOI: 10.1186/s11671-020-3283-5
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