What absorbs at 748 cm⁻¹ in an FTIR spectrum?
A band near 748 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 748 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 | 7 | 6 | 1.0 |
| Aromatic ring | 3 | 3 | 1.0 |
| Methyl | 2 | 2 | 1.0 |
| Hydroxyl (O-H) | 2 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Metal oxygen | 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 |
|---|---|---|---|
| PANi | 748, 2930, 1300 | Aromatic ring, 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 748 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
“903 901 902 903 C-H blending vibration of epoxide ring 748”
Imperiyka 等 - 2014 - Preparation and Characterization of Polymer Electr DOI: 10.1155/2014/638279 -
Alkyl C-H confidence 1.0
“Another specific band of aniline also are confirmed at 881 cm-1 cm-1 and 748 as bending vibration of C-H and wag vibration of N-H from primary amine.”
International Conference on Innovation on Polymer Science and Technology DOI: 10.1088/1757-899X/223/1/012051 -
confidence 1.0
“In addition, a weak broad band absorption cm-1 at wave number of 748 is attributed to vibration of Ti-O-Ti (7).”
Nizar 等 - 2018 - The Effect of Titanium Tetrahedral Coordination of DOI: 10.1088/1757-899X/335/1/012036 -
confidence 1.0
“Explicit assignment: stretching vibration modes at 720 and 748 correspond to HfO2.”
Pandey 等 - 2016 - Impact of post deposition annealing in O-2 ambient DOI: 10.1016/j.optmat.2014.08.005 -
confidence 1.0
“The peaks observed in the of range AC 720cm-1 748cm-1are to associated with the stretching vibration of bridging oxygen”
Yaacob 等 - 2018 - Comprehensive study on compositional modification DOI: 10.1016/j.solidstatesciences.2018.05.006 -
Alkyl C-H confidence 1.0
“The band at 986 is the bands at 1386.5 and 748 cm-1 are attributed to the α-methyl group vibrations.”
Awad 等 - 2020 - Experimental Investigation of Methyl Methacrylate DOI: 10.3390/ma13245793 -
Aromatic ring confidence 1.0
“propyl group appear at 2 933 In addition, aromatic C-H cm-1 cm-1, SEM imaging of CPR-loaded adsorbent bending and stretching appear at 748 and 3 030 respectively.”
Bajpai 等 - 2014 - The adsorptive removal of a cationic drug from aqu DOI: 10.4314/wsa.v40i1.6 -
confidence 1.0
“(O corresponds to oxygen from the corner of the heteropolyanion structure), W-O e-W c IR spectrum of PDPA doped with the PTA heteropolyanions is characterized by the IR (O corresponds to oxygen from the side of the heteropolyanion structure”
The Photoluminescence and Vibrational Properties of Black Phosphorous Sheets Chemically/Electrochemically Functionalized in the Presence of Diphenylamine DOI: 10.3390/polym14214479
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