What absorbs at 1171 cm⁻¹ in an FTIR spectrum?
A band near 1171 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 1171 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 | 8 | 7 | 1.0 |
| Secondary amine | 7 | 6 | 1.0 |
| C n single bond | 7 | 6 | 1.0 |
| Methacrylate | 6 | 6 | 1.0 |
| Acetate | 6 | 6 | 1.0 |
| Methoxy (OCH3) | 5 | 5 | 1.0 |
| C-O single bond | 5 | 5 | 1.0 |
| Alkyl C-H | 2 | 2 | 1.0 |
| Aromatic ring | 2 | 2 | 1.0 |
| Ester | 2 | 2 | 1.0 |
| Silicon-oxygen (Si-O) | 2 | 2 | 1.0 |
| Sulfate (SO4) | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Nitrogen heterocycle | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Ammonium | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| S eq o | 1 | 1 | 0.95 |
| Sulfonyl | 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 |
|---|---|---|---|
| magnetite | 1171, 1740, 1263 | Methacrylate | 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 1171 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
-
Acetate confidence 1.0
“FTIR spectrum (Figure 8) of produced FAME indicates the characteristic peak C=O cm-1 stretching band of methyl esters at 1740 and C-O stretching bands at 1171, 1197 and cm-1.”
Kanakdande 等 - 2019 - Pineapple Waste and Wastewater Route for Biodiese DOI: 10.1590/1678-4324-2019180499 -
Amide confidence 1.0
“A cm-1 sharp peak at 1171 explained the C-N stretching vibration of the pure crystal violet dye.”
Trichoderma asperellum laccase mediated crystal violet degradation–Optimization of experimental conditions and characterization DOI: 10.1016/j.jece.2016.11.044 -
Silicon (Si) confidence 1.0
“the bands observed at 953, 1076, and 1171cm-1 energy of electrons when they jump from higher energy are attributed to Si-O stretching vibrations.”
Ahmad 等 - 2021 - Spectroscopic Analysis for Harnessing the Quality DOI: 10.1155/2021/6629640 -
C-O single bond confidence 1.0
“cm-1 COO-), cm-1 1453 (CH scissoring), 1394 (C=O stretch of 1242 (asymmetric 2 cm-1 cm-1 PO stretch), 1171 (ester C-O symmetric stretch) and 1080 (CO stretch).”
Bel'skaya 等 - 2021 - Application of FTIR Spectroscopy for Quantitative DOI: 10.3390/diagnostics11122391 -
Ester confidence 1.0
“Moreover, a statistically cm-1, significant decrease in absorbance of the FTIR band at 1171 assigned to the -CO-O-Casymmetric stretching vibrations of cholesterol esters (Figure 3A), was observed only in the D-gal model [47].”
Spectroscopic Signature of Red Blood Cells in a D-Galactose-Induced Accelerated Aging Model DOI: 10.3390/ijms22052660 -
confidence 1.0
“characteristics for Si-O vibration of beryl and bands at 1014 cm-1 are characterize for internal Si-O stretching vibration while bands at 1171-1203 cm-1 are characteristics for Be-O vibration and Si-O stretching vibration (Reshma et al., 20”
Fawzy - 2021 - Separation of fine beryl from quartz via magnetic DOI: 10.37190/ppmp/132329 -
Acetate confidence 1.0
“The FTIR spectrum of HeLa cm-1 is ascribed to C-O stretching of proteins in at 1171 cells exhibited several bands representing changes in cancer cells (Rigas et al., 1990) and CO-O-C stretching of”
Knockdown of Death Receptor 5 Antisense Long Noncoding RNA and Cisplatin Treatment Modulate Similar Macromolecular and Metabolic Changes in HeLa Cells DOI: 10.55730/1300-0152.2634 -
Acetate confidence 1.0
“1171cm-1 ] 2858 2858 2858 sCH2 row band maximum at , followed with decreasing ]C=O intensity by well-defined peak maxima positioned at 1144 1745 1745 1752 (esters) 1100cm-1 ]C=O(acids/ketones)”
Invernizzi 等 - 2018 - Mid and Near-Infrared Reflection Spectral Database DOI: 10.1155/2018/7823248
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.