What absorbs at 750 cm⁻¹ in an FTIR spectrum?
A band near 750 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 750 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 | 21 | 18 | 1.0 |
| Aromatic ring | 14 | 12 | 1.0 |
| Metal oxygen | 9 | 8 | 1.0 |
| Boron nitrogen | 5 | 4 | 1.0 |
| Acetate | 4 | 3 | 1.0 |
| Silicon-oxygen (Si-O) | 3 | 3 | 1.0 |
| N h | 3 | 3 | 1.0 |
| Phosphate (PO4) | 3 | 3 | 1.0 |
| Hydrogen bond | 3 | 3 | 1.0 |
| Methacrylate | 3 | 3 | 1.0 |
| Amide | 3 | 3 | 1.0 |
| C c single bond | 3 | 3 | 1.0 |
| Silicon (Si) | 3 | 2 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| Secondary amine | 2 | 2 | 1.0 |
| C n single bond | 2 | 2 | 1.0 |
| Ring structure | 2 | 2 | 1.0 |
| Carboxyl (COOH) | 2 | 1 | 1.0 |
| Oxygen heterocycle | 2 | 0 | 1.0 |
| Water (H2O) | 2 | 0 | 1.0 |
| Sulfur heterocycle | 1 | 1 | 1.0 |
| C-S single bond | 1 | 1 | 1.0 |
| Silicon carbon | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| N eq o | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Borate | 1 | 1 | 1.0 |
| Methyl | 1 | 1 | 1.0 |
| Chlorine | 1 | 1 | 1.0 |
| Carbon dioxide | 1 | 1 | 0.9 |
| Bromine | 1 | 0 | 1.0 |
| Carbon bromine | 1 | 0 | 1.0 |
| Carbohydrate | 1 | 0 | 1.0 |
| Hydroxyl (O-H) | 1 | 0 | 0.9 |
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 |
|---|---|---|---|
| polypropylene | 750, 1030, 1600 | Alkyl C-H | 1 |
| PVC | 750, 834, 1195 | Alkyl C-H | 1 |
| ZnO | 750, 1400, 3430 | Metal oxygen, Alkyl C-H | 1 |
| Fe2O3 | 750, 1130, 1631 | Metal oxygen, Alkyl C-H | 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 750 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
-
confidence 1.0
“From the it 3 658cm-1 ρ can be seen that the changes in both V and with Fe 2O are almost is assigned to the TeO trigonal bipyramid (tbp) [38,39] a 3 4 750cm-1 ρ linear.”
Effects of Fe2O3 replacement of ZnO on elastic and structural properties of 80TeO2–(20−x)ZnO–xFe2O3 tellurite glass system DOI: 10.1016/j.jnoncrysol.2012.04.017 -
Boron nitrogen confidence 1.0
“There are two low-intensity peaks at ~750 and 1378 cm(cid:1)1 for B-N-B bending and B-N stretching modes, to be composed of agglomerates of nanocrystals resemAm respectively, for the h-BN phase.”
Chowdhury 等 - 2004 - Novel electrodeposition route for the synthesis of DOI: 10.1016/j.matlet.2004.05.079 -
Alkyl C-H confidence 1.0
“In addition, strong peaks can Molecules2023,28,4948 11of18 be seen at 750 cm-1, corresponding to the stretching vibration of the C-H band in the aro-”
Identifying, Quantifying, and Recovering a Sorbitol-Type Petrochemical Additive in Industrial Wastewater and Its Subsequent Application in a Polymeric Matrix as a Nucleating Agent DOI: 10.3390/molecules28134948 -
Alkyl C-H confidence 1.0
“cm-1, 20 corresponding to the CH stretching of the 750”
Kato 等 - 2005 - X-ray photoemission spectroscopy and Fourier trans DOI: 10.1116/1.1914816 -
Alkyl C-H confidence 1.0
“Effect of Fullerene on Cross-Link Density, cm-1 skeletal.34 A sharp peak at 750 is due to CH rocking 2 Young's Modulus and Water Resistance Property vibration of n-butyl group.”
Katiyar 等 - 2017 - Fullerene (C-60) Containing Cross-Linked Polyacryl DOI: 10.1166/jnn.2017.12880 -
confidence 1.0
“The peak at 750 cm-1 ascribed to C-Cl disappeared, indicating”
Understanding Hydrothermal Dechlorination of PVC by Focusing on the Operating Conditions and Hydrochar Characteristics DOI: 10.3390/app7030256 -
Acetate confidence 1.0
“Table4 Peakareasforreflectancemicro-FTIRspectra.AR1=areaof3100-3000cm-1/areaof3000-2800cm-1.AR2=areaof900-700cm-1/areaof3000-2800cm-1.%2960=areaofband centeredat2960cm-1/areaof3000-2800cm-1.%2920=areaofbandcenteredat2920cm-1/areaof3000-2800”
Geochemical and petrographic alteration of rapidly heated coals from the Herrin (No. 6) Coal Seam, Illinois Basin DOI: 10.1016/j.coal.2016.08.022 -
Metal oxygen confidence 1.0
“The peak at 750 cm-1 identifies the inner layer cm-1 vibration of Al-O-Si groups in illite [63,64].”
Varrica 等 - 2019 - ATR-FTIR Spectral Analysis and Soluble Components DOI: 10.3390/ijerph16142507
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