What absorbs at 1242 cm⁻¹ in an FTIR spectrum?
A band near 1242 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 1242 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 |
|---|---|---|---|
| Amide | 19 | 18 | 1.0 |
| Methacrylate | 18 | 16 | 1.0 |
| Acetate | 18 | 16 | 1.0 |
| C-O single bond | 18 | 16 | 1.0 |
| Methoxy (OCH3) | 15 | 13 | 1.0 |
| C n single bond | 8 | 8 | 1.0 |
| Alkyl C-H | 8 | 8 | 1.0 |
| Ester | 7 | 7 | 1.0 |
| Secondary amine | 7 | 7 | 1.0 |
| Carboxyl (COOH) | 6 | 6 | 1.0 |
| Nucleic acid | 4 | 4 | 1.0 |
| Phosphate (PO4) | 3 | 3 | 1.0 |
| Ketone | 3 | 3 | 1.0 |
| Carbonyl (C=O) | 3 | 3 | 1.0 |
| Carbohydrate | 3 | 3 | 1.0 |
| Fluorine (C-F) | 2 | 2 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| C c single bond | 2 | 2 | 1.0 |
| Lignin | 2 | 2 | 1.0 |
| Aromatic ring | 2 | 2 | 1.0 |
| Phosphorus | 1 | 1 | 1.0 |
| Sulfate (SO4) | 1 | 1 | 1.0 |
| Protein random coil | 1 | 1 | 1.0 |
| Protein beta sheet | 1 | 1 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| Borate | 1 | 1 | 1.0 |
| Siloxane (Si-O-Si) | 1 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Nitrate | 1 | 1 | 1.0 |
| Acetyl | 1 | 1 | 1.0 |
| N h | 1 | 1 | 0.95 |
| Alkene (C=C) | 1 | 1 | 0.9 |
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 |
|---|---|---|---|
| Cellulose | 1242, 1735, 1650 | Acetate, Methacrylate, C-O single bond | 1 |
| graphene oxide | 1242, 1150, 3400 | Methacrylate, Acetate, C-O single bond | 1 |
| asphalt binder | 1242, 1700, 1375 | Methacrylate, Acetate | 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 1242 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
“Figure 1 shows a schematic of a dielectric barman spectroscopy and mentioned that the absorption 1242cm-1 rier discharge (DBD) device which has been used to band at was attributed to the CH 2OH regenerate plasma throughout these experiments”
Characterization of Modified Tapioca Starch in Atmospheric Argon Plasma under Diverse Humidity by FTIR Spectroscopy DOI: 10.1088/0256-307X/30/1/018103 -
Acetyl confidence 1.0
“cm-1 The peak at 1242 of raw spectrum was EFB The moisture content (2-5%) seems to be necessary for attributed to a waxy acetyl group of hemicellulose ester the best reaction.”
Jahi 等 - 2020 - Empty Fruit Bunch Cellulose based Sorbent for Oil DOI: 10.17576/jsm-2020-4909-29 -
Acetate confidence 1.0
“This evidence is further supported by a strong band in 1050cm(cid:1)1 cm(cid:1)1 1250 region responsible for C-O absorption (1242.00 cm(cid:1)1).”
Green synthesis and biological evaluation of novel 5-fluorouracil derivatives as potent anticancer agents DOI: 10.1016/j.jsps.2019.09.013 -
Alkyl C-H confidence 1.0
“Similar to previous studies, SBS showed studies, SBS showed absorption reactions in the C=C bond and the C-H bond, with peaks absorption reactions in the C=C bond and the C-H bond, with peaks in the 700, 910, 966, cm-1 cm-1 cm(cid:2879)(cid”
Analysis of the Properties of Modified Asphalt Binder by FTIR Method DOI: 10.3390/ma15165743 -
Nitrate confidence 1.0
“monodentate nitrate species, indicated by split peaks at 1242 The lack of distinct features at 323 K for wavenumbers cm-1, cm-1 and 1295 shifted to lower wavenumbers and remained below 1500 makes it difficult to identify the individual”
Pena 等 - 2004 - Identification of surface species on titania-suppo DOI: 10.1021/jp0313122 -
Acetate confidence 1.0
“As for the bands at 1242 and cm-1, 1186 they refer to the stretching of C-O-C bands of epoxy, but mostly in the phenolic groups cm-1 present in the ramie fiber constituents [41].”
Pereira 等 - 2020 - Ballistic Performance of Ramie Fabric Reinforcing DOI: 10.3390/polym12112711 -
Acetate confidence 1.0
“The absorption peak at 1242 is because particle size of the Silica sol/MG resin composite modifier of the stretching of the C-O-C bond of the ether.”
Qin 等 - 2023 - Preparation and properties of silica solmelamine DOI: 10.1080/15685551.2022.2162280 -
Amide confidence 1.0
“The band at is assigned to C-N stretching mode of 1242cm-1 benzenoid ring.”
Rajakani 和 Vedhi - 2013 - Synthesis and electrochemical studies of TiO2 - Pa DOI: 10.4028/www.scientific.net/AMR.678.263
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