What absorbs at 2018 cm⁻¹ in an FTIR spectrum?
A band near 2018 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 2018 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 |
|---|---|---|---|
| Alkyl C-H | 5 | 5 | 1.0 |
| Carbohydrate | 3 | 3 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| Alkene (C=C) | 2 | 2 | 1.0 |
| Siloxane (Si-O-Si) | 1 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 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 |
|---|---|---|---|
| ZnO NPs | 2018, 1664, 875 | Alkyl C-H, Hydroxyl (O-H) | 1 |
| polyurethane | 2018, 2270, 1700 | Alkyl C-H | 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 2018 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
-
Carbohydrate confidence 1.0
“Zghari et al., 2018) also called wagging band (Manzato et al., 2017) confirms Mostly, the crystalline cellulose structure is related to the hydrogen well the unaltered crystalline cellulose II undergoing regenerbonding between intermolecula”
Structural characterization of Argania spinosa Moroccan wooden artifacts during natural degradation progress using infrared spectroscopy (ATR-FTIR) and X-Ray diffraction (XRD) DOI: 10.1016/j.heliyon.2019.e02477 -
Alkyl C-H confidence 1.0
“alkanes and the alkyl groups that could be attributed to the metal reduction peak (Alavi and Karimi, 2018).”
Green synthesis and characterization of titanium dioxide nanoparticles using leaf extract of Pouteria campechiana and larvicidal and pupicidal activity on Aedes aegypti DOI: 10.1016/j.envres.2021.111333 -
Alkene (C=C) confidence 1.0
“the stretching CH alkene stretching vibration (Raman 2018).”
Akkurt 等 - 2023 - Ability of Cupriavidus necator H16 to resist, bior DOI: 10.2166/wst.2023.188 -
Alkyl C-H confidence 1.0
“The band at 1099 on the other hand, decreased in the presence of oleic acyl groups, while the overlapping of the methylene rocking vibration and the Sustainability2018,10,4112 9of13 cm-1 out-of plane bending vibration of the cis-disubstitut”
Durazzo 等 - 2018 - Qualitative Analysis of Traditional Italian Dishes DOI: 10.3390/su10114112 -
Carbonyl (C=O) confidence 1.0
“detected in the spectra of the PUs between 3050 and 2800 The hard segments carbonyl bands Polymers 2018, 10, x FOR PEER REVIEW 7 of 17 cm-1 Polymers 2018, 10, x FOR PEER REVIEW 7 of 17 can be observed between 1705-1691 [30,34].”
Gregori Valdes 等 - 2018 - Synthesis and Characterization of Isosorbide-Based DOI: 10.3390/polym10101170 -
C c single bond confidence 1.0
“Thus, the bands at 940 and 936 are most rutinoside, and quercetin-3-O-glucoside This makes likely assigned to C-C and C-O vibration (Movasaghi et al., sense, since these compounds record high vibration intensity at 2018),whilethepeakat1,030”
Rapid Prediction of Fig Phenolic Acids and Flavonoids Using Mid-Infrared Spectroscopy Combined With Partial Least Square Regression DOI: 10.3389/fpls.2022.782159 -
Hydroxyl (O-H) confidence 1.0
“different which corresponded to presence of functional It was observed that biosynthesized ZnO NPs have C=C groups H-Br stretching (alkyl halides class), more stability for a very longer time without causing O=C=O different stretching (conj”
Iqtedar 等 - 2020 - Biosynthesis, optimization and characterization of DOI: 10.24275/rmiq/Bio1605 -
Alkyl C-H confidence 1.0
“ν(C-O)- ν(O-H)-bands between 1200 and 1450 as well as the decrease of the and at 3400 plus the Energies 2018, 11, x 8 of 12 cm-1 Energies 2018, 11, x 8 of 12 ν(C-H)-band at 2900 suggests a dehydration and partial aromatization of the materi”
Kruse 和 Zevaco - 2018 - Properties of Hydrochar as Function of Feedstock, DOI: 10.3390/en11030674
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