What absorbs at 1236 cm⁻¹ in an FTIR spectrum?
A band near 1236 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 1236 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 |
|---|---|---|---|
| Acetate | 17 | 16 | 1.0 |
| Amide | 16 | 16 | 1.0 |
| Methacrylate | 16 | 16 | 1.0 |
| C-O single bond | 15 | 15 | 1.0 |
| Methoxy (OCH3) | 14 | 14 | 1.0 |
| Alkyl C-H | 7 | 5 | 1.0 |
| Secondary amine | 5 | 5 | 1.0 |
| C n single bond | 5 | 5 | 1.0 |
| Phosphate (PO4) | 5 | 4 | 1.0 |
| Ester | 4 | 4 | 1.0 |
| Carboxyl (COOH) | 4 | 3 | 1.0 |
| Hydroxyl (O-H) | 3 | 3 | 1.0 |
| Phosphorus | 3 | 2 | 1.0 |
| Nucleic acid | 2 | 2 | 1.0 |
| Ketone | 2 | 2 | 1.0 |
| Carbonyl (C=O) | 2 | 2 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Hydrogen bond | 1 | 1 | 1.0 |
| Fluorine (C-F) | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Lignin | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Phospholipid | 1 | 1 | 1.0 |
| Protein beta sheet | 1 | 1 | 1.0 |
| Acetyl | 1 | 1 | 1.0 |
| Methyl | 1 | 1 | 0.8 |
| Silicon-oxygen (Si-O) | 1 | 1 | 0.6 |
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 |
|---|---|---|---|
| methylene blue | 1236, 1745, 1739 | Methacrylate, Acetate, Amide | 1 |
| cellulose nanocrystals | 1236, 1110, 1640 | Acetate, Methacrylate, C-O single bond | 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 1236 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
-
Phosphate (PO4) confidence 1.0
“0.14 0.01** Amide II 1542.34±1.54 1545.34±0.46 0.05* COO symmetric stretching 1396.38±2.09 1398.45±1.27 0.01** PO2 asymmetric stretching 1235.51±1.74 1250.20±0.57 0.01** C-O-C symmetric stretching 1156.29±1.22 1150.96±1.48 PO2 symmetric str”
Use of Fourier transform infrared spectroscopy for rapid comparative analysis of Bacillus and Micrococcus isolates DOI: 10.1016/j.foodchem.2008.08.063 -
Acetate confidence 1.0
“cm-1 in the spectrum of MB with 1664 this significantly sharp and strong peak at 1599 in thatofthemetabolites suggested theformationof carboxylgroups;the presenceof1082and 1236cm-1 peaks, associated with C-O stretching vibration,substantiat”
Biodegradation of Methylene Blue as an Evidence of Synthetic Dyes Mineralization during Textile Effluent Biotreatment by Acinetobacter pittii DOI: 10.1007/s40710-020-00443-6 -
Amide confidence 1.0
“In the Figure 1, in amide I vibrational region, are and 1236 respectively.”
Structural analysis of some soluble elastins by means of FTIR and 2D IR correlation spectroscopy DOI: 10.1002/bip.21524 -
Acetate confidence 1.0
“cm-1 Meanwhile, the peak at 1236 in raw TLWF spectrum is attributed to the C-O stretching vibration [26].”
Extraction and Characterization of Cellulose Nanocrystals from Tea Leaf Waste Fibers DOI: 10.3390/polym9110588 -
Amide confidence 1.0
“cm-1), cm-1), cm-1), (1450.65 C-N stretching (1394.53 amide III or C-N stretching (1235.67 CO-O-C cm-1), cm-1) symmetric stretching vibration (1073.59 stretching vibration of C-O groups ( 928.78 and”
Encapsulation of olive leaf phenolics within electrosprayed whey protein nanoparticles; production and characterization DOI: 10.1016/j.foodhyd.2019.105572 -
Alkyl C-H confidence 1.0
“A band observed at 1236 entails the antisymmetric C-H in-plane bending”
Velhal 等 - 2018 - Structural, electrical and microwave properties of DOI: 10.1088/2053-1591/aadaf7 -
Acetate confidence 1.0
“The absorption peak at 1236 of the pyrimidine ring, the out-of-plane swinging of the C O tortion cm-1is characterized by molecular vibrations, including the distorbonds, and the stretching and swinging of the C H and N H bonds.”
A comparative study on the experimental and calculated results of mid-infrared and Raman vibrational modes of nucleic acid bases DOI: 10.1016/j.jmgm.2017.04.016 -
Amide confidence 1.0
“[46], the peak at 1145 the amide band that accounts for the peak at 1236 cm-1[45].”
Antibacterial Activity of the Green Synthesized Plasmonic Silver Nanoparticles with Crystalline Structure against Gram-Positive and Gram-Negative Bacteria DOI: 10.3390/nano13081327
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