What absorbs at 1549 cm⁻¹ in an FTIR spectrum?
A band near 1549 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 1549 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 | 15 | 13 | 1.0 |
| Carbonyl (C=O) | 4 | 4 | 1.0 |
| N h | 3 | 3 | 1.0 |
| Alkene (C=C) | 3 | 3 | 1.0 |
| Carboxyl (COOH) | 3 | 3 | 1.0 |
| Alkyl C-H | 2 | 2 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| Ketone | 2 | 2 | 1.0 |
| Ester | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Chitosan | 1 | 1 | 1.0 |
| Carbonate | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
| C=n | 1 | 1 | 1.0 |
| C c single bond | 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 |
|---|---|---|---|
| MWCNT | 1549, 2876, 1430 | N h | 1 |
| MCM-41 | 1549, 2170, 1655 | N h | 1 |
| CMC | 1549, 1423, 1196 | Amide, Carbonyl (C=O) | 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 1549 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
-
Alkene (C=C) confidence 1.0
“and C-H plane bending at 1083 These are associated with the bipolaran structure and the cm-1 peak at 1549 is related to the C=C stretching mode [49].”
Highly Biological Active Antibiofilm, Anticancer and Osteoblast Adhesion Efficacy from MWCNT/PPy/Pd nanocomposite DOI: 10.1016/j.apsusc.2017.10.142 -
Carboxyl (COOH) confidence 1.0
“of others 4 cm-1 authors, they observed an infrared (IR) absorption band located between 1549 [23-26] and cm-1 (COO1555 [8,25], which was attributed to the asymmetric stretching of the carboxyl group ).”
Adsorption mechanisms of fatty acids on fluorite unraveled by infrared spectroscopy and first-principles calculations DOI: 10.1016/j.jcis.2020.09.062 -
Alkene (C=C) confidence 1.0
“Explicit assignment: '1549' as part of C=C”
Shi 等 - 2006 - The investigation of argon plasma surface modifica DOI: 10.1016/j.eurpolymj.2006.01.007 -
C c single bond confidence 1.0
“cm-1 This was evidenced by the appearance of a clearly discernible band at 2275 corresponding to asymmetric stretching of the appended terminal isocyanate groups, and the appearance of an aromatic cm-1 C-C stretch at 1549 in the FTIR spectr”
Synthesis and Characterization of Mesoporous Silica Functionalized with Calix[4]arene Derivatives DOI: 10.3390/ijms131013726 -
confidence 1.0
“The formation of new N-acyl urea linkages between the adsorbed CMC repeat units can then possibly explain the observed cm1 cm1 1639 (C = O stretching, CONH) and 1549 peak (N-H bending)(Posthumus et al.”
Azrak 等 - 2021 - Controlled Dispersion and Setting of Cellulose Nan DOI: 10.21203/rs.3.rs-376512/v1 -
Amide confidence 1.0
“Drugs2018,16,211 6of19 The PSC and ASC amide II bands were situated at wavenumbers of 1548.95 and 1545.17 cm-1 respectively;”
Ben Slimane 和 Sadok - 2018 - Collagen from Cartilaginous Fish By-Products for a DOI: 10.3390/md16060211 -
Amide confidence 1.0
“LLM confirmed rule peak-group candidate”
Bujok 等 - 2019 - Applicability of FTIR-ATR Method to Measure Carbon DOI: 10.1155/2019/2181370 -
Amide confidence 1.0
“As shown in Figure 5 and Table S3, the spectrum of FG exhibits characteristic cm-1, cm-1, cm-1, cm-1 cm-1, absorption bands at 1656 1549 1240 3327 and 2958 which absorption bands at 1656 cm-1, 1549 cm-1, 1240 cm-1, 3327 cm-1 and 2958 cm-1,”
Interaction between Negatively Charged Fish Gelatin and Cyclodextrin in Aqueous Solution: Characteristics and Formation Mechanism DOI: 10.3390/gels7040260
Have a spectrum with this band?
Upload your FTIR spectrum and get a full interpretation report — peak assignments with literature citations, library matches, and a literature-backed analysis — in seconds.