What absorbs at 1180 cm⁻¹ in an FTIR spectrum?
A band near 1180 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 1180 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 |
|---|---|---|---|
| C-O single bond | 24 | 21 | 1.0 |
| Methoxy (OCH3) | 19 | 17 | 1.0 |
| Methacrylate | 19 | 17 | 1.0 |
| Acetate | 19 | 17 | 1.0 |
| Amide | 9 | 9 | 1.0 |
| Alkyl C-H | 6 | 6 | 1.0 |
| N h | 5 | 5 | 1.0 |
| Secondary amine | 5 | 5 | 1.0 |
| C n single bond | 5 | 5 | 1.0 |
| Aromatic ring | 5 | 5 | 1.0 |
| Siloxane (Si-O-Si) | 5 | 4 | 1.0 |
| Silicon-oxygen (Si-O) | 5 | 3 | 1.0 |
| Ester | 4 | 4 | 1.0 |
| Carboxyl (COOH) | 4 | 4 | 1.0 |
| Hydroxyl (O-H) | 4 | 3 | 1.0 |
| Ketone | 3 | 3 | 1.0 |
| Carbonyl (C=O) | 3 | 3 | 1.0 |
| Nucleic acid | 3 | 3 | 1.0 |
| C c single bond | 2 | 2 | 1.0 |
| Oxygen heterocycle | 2 | 2 | 1.0 |
| Fluorine (C-F) | 2 | 2 | 1.0 |
| Phosphate (PO4) | 2 | 1 | 1.0 |
| Silicon (Si) | 2 | 1 | 1.0 |
| S eq o | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Protein | 1 | 1 | 1.0 |
| Chitosan | 1 | 1 | 1.0 |
| Metal oxygen | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Silanol (Si-OH) | 1 | 1 | 1.0 |
| Sulfate (SO4) | 1 | 1 | 1.0 |
| N c o | 1 | 1 | 1.0 |
| Borate | 1 | 1 | 1.0 |
| Hydrogen bond | 1 | 1 | 1.0 |
| Chlorine | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| Silicon nitrogen | 1 | 1 | 1.0 |
| N-O 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 |
|---|---|---|---|
| zinc oxide | 1180, 1627, 1638 | Methacrylate, Acetate, C-O single bond | 1 |
| PVDF | 1180, 1160, 840 | Methacrylate, Acetate | 1 |
| MgO | 1180, 699, 874 | Methoxy (OCH3), Methacrylate, C-O single bond | 1 |
| PHB | 1180, 3440, 1724 | Methacrylate, Acetate, Methoxy (OCH3) | 1 |
| PLLA | 1180, 1182, 921 | C-O single bond, Methoxy (OCH3), Methacrylate | 1 |
| CS | 1180, 1645, 1720 | Methacrylate, C-O single bond, 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 1180 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
-
N-O bond confidence 1.0
“film 1170cm-1 1180cm-1 same from to suggesting possible transformation from to This showed no film apparent defect on its surface.”
Arshad 等 - 2019 - Dielectric and Structural Properties of Poly(vinyl DOI: 10.1155/2019/5961563 -
C-O single bond confidence 1.0
“3400-3200 3450 ~3325 C─O─C 1140-1070 stretch/ether stretch 1180, 1031 1179, 1028 48404 (4 of 9) J.APPL.POLYM.SCI.2019, DOI: 10.1002/APP.48404 ARTICLE”
Influence of amine‐terminated additives on thermal and mechanical properties of diglycidyl ether of bisphenol A (DGEBA) cured epoxy DOI: 10.1002/app.48404 -
confidence 1.0
“[Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.] cm21 et al [41] proposed a mechanism for twist banding, which are assigned reported [7, 30] that the bands at 1180 C(cid:1)(cid:1)O(cid:1)(cid:1”
Effect of processing conditions on the development of morphological features of banded or nonbanded spherulites of poly(3hydroxybutyrate) (PHB) and polylactic acid (PLLA) blends DOI: 10.1002/pen.21991 -
C-O single bond confidence 1.0
“The FTIR spectroscopy study of neat PLA having various functional groups C=O al cm-1), cm-1), stretching vibrations (~ 1749 asymmetric C-O-C stretching (1180 symmetric and cm-1), cm-1), asymmetric -CH vibrations (1128 and 1042 C-OH side gro”
Ghosh 等 - 2020 - Blown films fabrication of poly lactic acid based DOI: 10.1016/j.mtcomm.2019.100737 -
confidence 1.0
“Si-O Si-O symmetric stretching 1040 - [2,16] 2(cid:3)1019 N-H N-H wag-rocking 1150 [15] Si-O Si-O asymmetric stretching 1180 - [2,16] 7(cid:3)1019 2000 [15] Si-H H-Si-Si3”
Effect of PECVD silicon oxynitride film composition on the surface passivation of silicon wafers DOI: 10.1016/j.solmat.2011.09.052 -
Aromatic ring confidence 1.0
“N=O (NO ) symmetric stretching 1340 2 C-N stretching (aryl) 1180 In plane aromatic C-H deformation”
Synthesis and characterization of Heck-cross coupling 4-(4-nitrostyryl) aniline as potential precursor in Schiff-base synthesis DOI: 10.1063/1.5002293 -
confidence 1.0
“A weak absorption peak at 450 cm-1 corresponds to the Si-N stretching while a N-H bending peak is also observed at 1180 cm-1 [20].”
Deposition of Silicon Nitride Films using Chemical Vapor deposition for Photovoltaic Applications DOI: 10.1016/j.rinp.2016.11.029 -
confidence 1.0
“(iii) Two successive distinct broad bands with the first extended It is to be mentioned that the clear identification and strong -1 from 780 to 1150 cm and showing two peaks at 930 and appearance of the vibrational bands due to both borate”
Marzouk 等 - 2021 - Judd-Ofelt analysis of spectroscopic measurements DOI: 10.1016/j.molstruc.2021.130925
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