What absorbs at 1234 cm⁻¹ in an FTIR spectrum?
A band near 1234 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 1234 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 |
|---|---|---|---|
| Methacrylate | 17 | 17 | 1.0 |
| Acetate | 17 | 17 | 1.0 |
| C-O single bond | 14 | 14 | 1.0 |
| Methoxy (OCH3) | 13 | 13 | 1.0 |
| Amide | 13 | 13 | 1.0 |
| Ester | 6 | 6 | 1.0 |
| Alkyl C-H | 5 | 5 | 1.0 |
| Phosphate (PO4) | 5 | 4 | 1.0 |
| Ketone | 4 | 4 | 1.0 |
| Carboxyl (COOH) | 4 | 4 | 1.0 |
| Carbonyl (C=O) | 4 | 4 | 1.0 |
| Nucleic acid | 4 | 3 | 1.0 |
| Secondary amine | 3 | 3 | 1.0 |
| C n single bond | 3 | 3 | 1.0 |
| Ring structure | 3 | 2 | 1.0 |
| Carbohydrate | 2 | 2 | 1.0 |
| Acetyl | 2 | 2 | 1.0 |
| Methyl | 2 | 2 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Sulfate (SO4) | 1 | 1 | 1.0 |
| S eq o | 1 | 1 | 1.0 |
| Lipid | 1 | 1 | 1.0 |
| Protein beta sheet | 1 | 1 | 1.0 |
| Protein | 1 | 1 | 1.0 |
| Metal oxygen | 1 | 1 | 1.0 |
| Siloxane (Si-O-Si) | 1 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Lignin | 1 | 1 | 1.0 |
| Amino acid | 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 |
|---|---|---|---|
| Epoxy | 1234, 1660, 1735 | Methacrylate, Acetate, C-O single bond | 1 |
| polyurethane | 1234, 2270, 1700 | Methacrylate, Acetate, C-O single bond | 1 |
| epoxy resin | 1234, 905, 1100 | Methacrylate, Acetate, Methoxy (OCH3) | 1 |
| cellulose nanocrystals | 1234, 1110, 1640 | Acetate, Methacrylate, C-O single bond | 1 |
| alginate | 1234, 1100, 1715 | Methacrylate, Acetate, Methoxy (OCH3) | 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 1234 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
-
C-O single bond confidence 1.0
“C-O-C stretching in esters 1161 (m) 1155 (s) 1159 (s) C-O-C stretching in esters 1234 (w)”
Barnaby 等 - 2018 - Free Radical Scavenging Capacity, Carotenoid Conte DOI: 10.1155/2018/1762342 -
Amino acid confidence 1.0
“stretching mode of groups of serine, threonine, and tyrosine of proteinEE A comparison of the spectra showed significant changes in AmideIII(NAHbending,CANstretch,CACstretch) 1234 Amide III absorbance throughout the whole range tested, i.e.”
Application of infrared spectroscopy in the identification of Ewing sarcoma: A preliminary report DOI: 10.1016/j.infrared.2017.05.006 -
Amide confidence 1.0
“the case of cancerous tissues in peak at 1234 This characteristic absorption band belongs to amide III and it appeared mainly due N-H bending, C-N stretch, C-C stretching vibrations in bone tissue [22].”
Chaber 等 - 2017 - Fourier Transform Infrared (FTIR) spectroscopy of DOI: 10.1016/j.infrared.2017.07.017 -
Acetate confidence 1.0
“Changes in the peaks of the FTIR spectrum at 2852 cm-1 (C-H stretching), 1732 (C=O stretching) and 1234 (C-O stretching) indicated that the alkali treatment completely removed hemicelluloses and lignin from the fiber surface.”
Isolation and Characterization of Cellulose Nanocrystals from Oil Palm Mesocarp Fiber DOI: 10.3390/polym9080355 -
Ring structure confidence 1.0
“cm-1 The existence of the epoxide ring in the purified ENR-25 is shown by peak at 875 due to half ring stretching of the epoxide while the full ring stretching is at 1234 cm-1 [9].”
Dahham 等 - 2018 - The Influences of Zirconium Dioxide on ENR-25ZrO2 DOI: 10.1088/1742-6596/1019/1/012055 -
Amide confidence 1.0
“The vibrational bands at 1299 1234 cm-1 20 π-delocalized and 1112 have been assigned to the protonation level of PANI-ES due to the AC C-N+ 21 electrons and interpreted as a stretching vibration of the polaron structure, and to the”
Multimorphologies of Hydrochloride Polyaniline Synthesized by Conventional and Interfacial Polymerization DOI: 10.1016/j.molstruc.2017.04.104 -
Alkyl C-H confidence 1.0
“cm-1 In addition, the leaf spectra detected a medium peak at 2917.81 and a strong peak at cm-1, 1233.97 indicative of the C-H (stretching) group of alkanes and the C-O (stretching) group of alkyl aryl ethers, respectively.”
Phytochemical Composition of Combretum molle (R. Br. ex G. Don.) Engl. & Diels Leaf and Stem Extracts DOI: 10.3390/plants12081702 -
Amide confidence 1.0
“Control, Pe5, Pe15, and Pe25 exhibited their characteristic amide III peak at wavenumcm-1, bers 1234, 1226, 1226, and 1224 respectively.”
Ahmad 等 - 2021 - Recovery of Gelatin from Bovine Skin with the Aid DOI: 10.3390/polym
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