What absorbs at 736 cm⁻¹ in an FTIR spectrum?
A band near 736 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 7 cited sources
Quick answer
A band near 736 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 |
|---|---|---|---|
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| Alkyl C-H | 2 | 2 | 1.0 |
| Carbonyl (C=O) | 2 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| Nitrogen heterocycle | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| Carbonate | 1 | 0 | 0.6 |
Ranking reflects accumulated literature evidence, not a single authoritative 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 736 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
-
Silicon (Si) confidence 1.0
“smaller peaks at 736 and 697 both ascribed to Si-phenyl 6.”
Modification of Chrysotile Surface by Organosilanes: An IR–Photoacoustic Spectroscopy Study DOI: 10.1006/jcis.2001.7524 -
Nitrogen heterocycle confidence 1.0
“LLM confirmed rule peak-group candidate”
Wang 等 - 2014 - Target Synthesis of a Novel Porous Aromatic Framew DOI: 10.6023/A14020121 -
Alkyl C-H confidence 1.0
“Bands at 736 and 873 in OneFill suggested cm-1, cm-1, cm-1, the presence of C-H bending.”
Assiry 等 - 2023 - Microstructural and Elemental Characterization of DOI: 10.3390/app13074517 -
Alkyl C-H confidence 1.0
“In the FTIR spectra of the NCE, 1090, 2080, 3070, and 4060 polymers, the 729-, 744-, 744-, 729-, In the FTIR spectra of the NCE, 1090, 2080, 3070, and 4060 polymers, the 729-, 744-, 744-, 729-, and 736-cm-1 and 736-cm-1 peaks are δCH (out-o”
Li 等 - 2019 - Blends of Cyanate Ester and Phthalonitrile-Polyhed DOI: 10.3390/polym11010054 -
Acetate confidence 1.0
“Signals at 736 cm-1, 1212 cm-1 and 1047 cm-1 corresponded to 1047 and 900 Signals at 736 1212 and 1047 corresponded to -C=O, -C-C-Oand -C-O groups, respectively, representing the characteristics of CTA -C=O, -C-C-Oand -C-O groups, respectiv”
Membrane Fouling Behavior of Forward Osmosis for FruitJuice Concentration DOI: 10.3390/membranes11080611 -
Acetate confidence 1.0
“Further, a furan ring was and out-of-plane wagging deformation were detected at 3327 Further, a furan ring detected by characteristic peaks at 1011 and 736 cm-1 that were caused by C-O-C antisymcm-1”
Wen 等 - 2021 - Development of Low-Viscosity and High-Performance DOI: 10.3390/ma -
confidence 0.9
“Explicit assignment in text.”
Uner 等 - 2016 - Centaurea solstitialis and Silybum marianum weeds DOI: 10.1007/s13726-015-0396-2
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