What absorbs at 1175 cm⁻¹ in an FTIR spectrum?
A band near 1175 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 1175 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 | 12 | 9 | 1.0 |
| Methoxy (OCH3) | 11 | 8 | 1.0 |
| Methacrylate | 11 | 8 | 1.0 |
| Acetate | 11 | 8 | 1.0 |
| Silicon-oxygen (Si-O) | 4 | 4 | 1.0 |
| Amide | 4 | 4 | 1.0 |
| Carbohydrate | 4 | 4 | 1.0 |
| Secondary amine | 3 | 3 | 1.0 |
| C n single bond | 3 | 3 | 1.0 |
| Alkyl C-H | 3 | 3 | 1.0 |
| Silicon (Si) | 2 | 2 | 1.0 |
| Siloxane (Si-O-Si) | 2 | 2 | 1.0 |
| C c single bond | 2 | 2 | 1.0 |
| Ring structure | 2 | 2 | 1.0 |
| N h | 2 | 2 | 1.0 |
| Aromatic ring | 2 | 2 | 1.0 |
| Fluorine (C-F) | 2 | 1 | 1.0 |
| N-O bond | 1 | 1 | 1.0 |
| Oxygen heterocycle | 1 | 1 | 1.0 |
| Phosphorus | 1 | 1 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 1.0 |
| Sulfur | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Silicon hydride | 1 | 1 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Metal oxygen | 1 | 1 | 1.0 |
| Quinone | 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 |
|---|---|---|---|
| polyurethane | 1175, 2270, 1700 | Methacrylate, Acetate, C-O single bond | 1 |
| TiO2 | 1175, 1700, 1093 | Methacrylate, Acetate, C-O single bond | 1 |
| polyaniline | 1175, 1565, 1570 | Methacrylate, Acetate | 1 |
| humic acid | 1175, 1660, 1220 | Methacrylate, Acetate, Methoxy (OCH3) | 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 1175 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
-
Alkyl C-H confidence 1.0
“In 4FBN, the C@Ostretchingvibrationsoccurat1713 1014cm(cid:2)1 cm(cid:2)1inIRand1705cm(cid:2)1peaks observed in IR at 1175, 1117 and and in Raman, 998cm(cid:2)1 1173, 1110 and are assigned to C-H in-plane bending in Raman spectra.”
Arjunan 等 - 2012 - Quantum chemical studies and vibrational analysis DOI: 10.1016/j.saa.2012.08.053 -
Alkyl C-H confidence 1.0
“Raman band at 1175 is assigned to C-H out-plane bending vibration of quinone ring.”
Jin 等 - 2018 - Polymer anode used in hydrometallurgy Anodic beha DOI: 10.1016/j.hydromet.2018.01.020 -
confidence 1.0
“Then, after 5 min of the reaction, peaks at 1175 and 1063 can be observed with the asymmetric stretching of Si-O-Si and Al-O-Si.”
Alumino-Silicate Structural Formation during Alkali-Activation of Metakaolin: In-Situ and Ex-Situ ATR-FTIR Studies DOI: 10.3390/ma16030985 -
Acetate confidence 1.0
“The band at 1175 belonged to obtained in the present work is much higher than the other C-O stretching (Darvishi et al.”
Synthesis of photocatalytic zinc oxide nanoflowers using Peltophorum pterocarpum pod extract and their characterization DOI: 10.1007/s13204-021-01919-z -
Carbonyl (C=O) confidence 1.0
“or poorly organized hydrogen bonded carbonyl groups are still Interestingly, no noticeable change in peaks between 1175 and present at equilibrium, as indicated by the sizes of the 1733 and cmK1 cmK1 1425 are observed.”
Yilgor 等 - 2006 - FTIR investigation of the influence of diisocyanat DOI: 10.1016/j.polymer.2006.02.027 -
Aromatic ring confidence 1.0
“1208 -C=Cwith aromatic bending -SO3anti-symmetric stretching 1175 -C-H aromatic 1126”
Benbow 等 - 2018 - A Novel Soft Contact Piezo-Controlled Liquid Cell DOI: 10.1038/s41598-018-34673-4 -
Acetate confidence 1.0
“cm-1 and intensive C-O stretching band at 1260 (aryl ethers) and relatively intensive bands cm-1 and/or shoulders at 1220 (C-O stretching and O-H bending of carboxylic groups, cm-1 C-O stretching in phenoxy structures and ethers) and 1175 (”
Polarity-Based Sequential Extraction as a Simple Tool to Reveal the Structural Complexity of Humic Acids DOI: 10.3390/agronomy11030587 -
Acetate confidence 1.0
“The bands at 1175, 1605 and 1023 cm-1 corresponded to C-O stretching frequencies of (C-O-C), which are stereotypical of the polysaccharide backbone.”
Gad 等 - 2021 - Synergistic Effect of Titanium Dioxide (TiO2) and DOI: 10.21203/rs.3.rs-161064/v2
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