What absorbs at 1165 cm⁻¹ in an FTIR spectrum?
A band near 1165 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 1165 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 |
|---|---|---|---|
| Methoxy (OCH3) | 12 | 12 | 1.0 |
| Methacrylate | 12 | 12 | 1.0 |
| Acetate | 12 | 12 | 1.0 |
| C-O single bond | 11 | 11 | 1.0 |
| Alkyl C-H | 8 | 8 | 1.0 |
| Silicon-oxygen (Si-O) | 5 | 5 | 1.0 |
| Aromatic ring | 4 | 4 | 1.0 |
| C c single bond | 3 | 3 | 1.0 |
| Ring structure | 3 | 3 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| Phosphate (PO4) | 2 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| Hydrogen bond | 1 | 1 | 1.0 |
| Methyl | 1 | 1 | 1.0 |
| S eq o | 1 | 1 | 1.0 |
| Metal oxygen | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Borate | 1 | 1 | 1.0 |
| Siloxane (Si-O-Si) | 1 | 1 | 1.0 |
| Carbohydrate | 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 | 1165, 1735, 1650 | Acetate, Methacrylate, C-O single bond | 1 |
| silica | 1165, 1100, 1080 | 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 1165 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
-
confidence 1.0
“low pH (#1.63) and high water cm21 The peaks appearing at about 1165 (longitudinal optic content (H 2O/TEOS~4), the rate of hydrolysis would be high stretching24,25) (LO) component of Si-O-Si asym.”
De 等 - 2000 - Hydrolysis-condensation reactions of TEOS in the p DOI: 10.1039/B003221M -
Borate confidence 1.0
“Furthermore, antisymmetrical tween 500 and 1400 Moreover, the reflectivity was at 0.4%-1%, 1.05-1.10 stretching of B-O brought the absorption peaks at 1165 and low values of and at the wavelength of cm-1[7,10,11].”
Preparation and properties of nanocrystal SmBO3 by nitrate-citrate sol-gel combustion method DOI: 10.1016/S1002-0721(08)60225-2 -
Ring structure confidence 1.0
“Justice Basheer Ahmed Sayeed cm-1 FTIRATR spectral peaks were obtained (1165 for ring vibration mode of C-O-H College for Women, Chennai - cm-1 and C-O-C bonds cholesterol ester with phosphoric acid, 1742 responsible for C=O 600018, Tamil N”
Khatheeja 等 - 2019 - COMPARATIVE STUDIES ON BIOCHEMICAL, HISTOPATHOLOGI DOI: 10.13040/IJPSR.0975-8232.10(2).836-45 -
confidence 1.0
“Another source of CO gas was produced cm(cid:0) 1 Si-O-C The peak that appeared at 1165 from the Boudouard reactions (5) spontaneously which had a negative can be related to the mol(cid:0) 1 = (cid:0) (ΔG Si-O-Si”
Ultra-fine beta SiC nanowires Isothermally converted from high activated silica by Carbothermic Reduction and Carburization at low temperature DOI: 10.1016/j.matchemphys.2020.123716 -
Acetate confidence 1.0
“The change of CI and crystallite size by larly, the band at 1165 assigned as C-O-C stretchb-(1!4)-glucosidic”
Oh 等 - 2005 - Crystalline structure analysis of cellulose treate DOI: 10.1016/j.carres.2005.08.007 -
Acetate confidence 1.0
“Other bands in the region of 1165 to A cm-1 1021 are almost similar for all the samples and are due to asymmetric C-O-C stretching, asymmetric in phase ring stretching, and C-O/C-C stretching vibrations (Table 1) that are”
Rout 等 - 2017 - A green approach to produce silver nano particles DOI: 10.1016/j.surfin.2017.03.004 -
confidence 1.0
“As per the FTIR spectrum, a characteristic peak of Si-O-Zn at 1165 was observed, indicating that T-ZnOw was successfully modified by KH-570.”
Lipophilic modification of T-ZnOw and optical properties of T-ZnOw/PVB composite films DOI: 10.1007/s00339-020-3436-5 -
Acetate confidence 1.0
“Peaks at 1082 and 14 focused on the vibration modes of absorbance peaks cm-1 1165 are induced by vibration of C-O and bending”
Zou 等 - 2016 - Whole blood and semen identification using mid-inf DOI: 10.1039/C5AY03337C.
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