What absorbs at 757 cm⁻¹ in an FTIR spectrum?
A band near 757 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 757 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 | 3 | 3 | 1.0 |
| Carboxyl (COOH) | 2 | 2 | 1.0 |
| Aromatic ring | 2 | 2 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| Phosphorus | 1 | 1 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 1.0 |
| C-S single bond | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
Ranking reflects accumulated literature evidence, not a single fixed rule. Always confirm against your sample context.
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 757 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
-
Hydroxyl (O-H) confidence 1.0
“4 sites (B-type) or hydroxide sites (A-type) of apatite, the band positions are assigned differently for the A-type (757 cm-1).”
Awonusi 等 - 2007 - Carbonate assignment and calibration in the raman DOI: 10.1007/s00223-007-9034-0 -
Alkyl C-H confidence 1.0
“removing residual reactants and byproducts, Open cm(cid:1)1 -CH peak appearing at 757 possibly represents the”
Surface-initiated atom transfer radical polymerization grafting from nanoporous cellulose gels to create hydrophobic nanocomposites DOI: 10.1039/c8ra04163f -
Silicon-oxygen (Si-O) confidence 1.0
“The most inaction (Figure 3(b)), the morphology of the geopolymer is tensive band at 998 was due to Si-O-Al stretching vi757cm-1 constituted by a chain of polysilicate layers by the combration.”
El Alouani 等 - 2019 - Preparation, Characterization, and Application of DOI: 10.1155/2019/4212901 -
Acetate confidence 1.0
“cm(cid:0) cm(cid:0) 1 1 1 1 and 843 (stretching of C-O-C in epoxy), 757 (epoxide in A-PGMA (being masked by a broad band) and is strongly cm(cid:0) 1 -OH (due to, primary alcohol ring) [35,37,60].”
Functionalization of poly(glycidylmethacrylate) with iminodiacetate and imino phosphonate groups for enhanced sorption of neodymium - sorption performance and molecular modeling DOI: 10.1016/j.reactfunctpolym.2022.105389 -
Alkyl C-H confidence 1.0
“C-H Aromatic vibration mode 790-569 cm-1 C-H Out-of-plane bending vibration 757 cm-1”
Influence of Waste Toner on Asphalt Binder: Chemical and Rheological Characterization DOI: 10.3390/molecules28062794 -
C-S single bond confidence 1.0
“[δ(CH)], 3+)], 1380c 1360c symb(NH )], and changes indicate the following: (1) the presence of cystine in cm-1 cm-1, [(ρ C-S 1326c w(CH 2)] SEIRA signals increase in intensity P C-G) and two one rotamer on AgNPs (at 757 cm-1) compared to th”
Proniewicz 等 - 2021 - Is the Use of Surface-Enhanced Infrared Spectrosco DOI: 10.1021/acs.jpcb.1c00546 -
Carboxyl (COOH) confidence 1.0
“757/784 827/811 acid bands, such as and Glycogen bands were demonstrated to play an important role as a discriminant spectral marker”
Vibrational Spectroscopy for In Vitro Monitoring Stem Cell Differentiation DOI: 10.3390/molecules25235554 -
confidence 1.0
“Also, peak at 757cm-1 indicates crystallization technique presence of halogen-hydrogen interaction.”
Shete 等 - 2018 - Solid State Characterization and Tableting Studies DOI: 10.5530/ijper.52.1.8
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