What absorbs at 1768 cm⁻¹ in an FTIR spectrum?
A band near 1768 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 3 cited sources
Quick answer
A band near 1768 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 |
|---|---|---|---|
| Carbonyl (C=O) | 3 | 3 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| Ketone | 2 | 2 | 1.0 |
| Ester | 2 | 2 | 1.0 |
| Carboxyl (COOH) | 2 | 2 | 1.0 |
| Amide | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| N h | 1 | 1 | 1.0 |
Ranking reflects accumulated literature evidence, not a single authoritative rule. Always confirm against your sample context.
Possible materials
| Material | Supporting peaks | Overlapping groups | Cited sources |
|---|---|---|---|
| polyimide | 1768, 1720, 1778 | Carbonyl (C=O), 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 1768 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
“ence electrode with a scan rate of 100 mV is attributed to N-H stretching vibration and the cm(cid:2)1 cm(cid:2)1 vibration at around 1768 Under these conditions, the cyclic voltammetry of and 1712 aristhe polyimide shows two pairs of rever”
Chao 等 - 2007 - Electroactive polyimide with oligoaniline in the m DOI: 10.1016/j.eurpolymj.2007.03.048 -
Acetate confidence 1.0
“cm1 cm-1 Peak at 1768 obtained was due to C=O whereas at 1713 the peak corresponded to cm-1 cm-1 benzene ring.”
Bhattacharyya 等 - 2017 - Metallization and APPJ treatment of bismaleimide DOI: 10.1155/2010/987357 -
Acetate confidence 1.0
“The disappearance of the νas(α-C=O) band with the maximum at 1768 cm-1 occurs relatively quickly, while the νs(β-C=O) band intensity at 1758 cm-1 decreases more slowly.”
Tisovsky 等 - 2017 - Effect of Structure on Charge Distribution in the DOI: 10.3390/molecules22111961
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