What absorbs at 1345 cm⁻¹ in an FTIR spectrum?
A band near 1345 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 1345 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 |
|---|---|---|---|
| Alkyl C-H | 7 | 7 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| N-O bond | 1 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| Chitosan | 1 | 1 | 1.0 |
| Metal oxygen | 1 | 1 | 1.0 |
| N h | 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 |
|---|---|---|---|
| TiO2 | 1345, 1700, 1093 | Alkyl C-H, Methacrylate, C-O single bond | 1 |
| alumina | 1345, 460, 1000 | Alkyl C-H | 1 |
| chitosan | 1345, 1650, 1655 | Alkyl C-H, Methacrylate, C-O single bond | 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 1345 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
“B.Bozzinietal./JournalofPowerSources195 (2010) 4119-4123 4123 C Oasymmetricstretchinginacetate), wereobservedat1330(O 1340/1345cm-1 (OH and CH wagging combination of ethanol”
In situ spectroelectrochemical measurements during the electro-oxidation of ethanol on WC-supported Pt-black, based on sum-frequency generation spectroscopy DOI: 10.1016/j.jpowsour.2010.01.017 -
Metal oxygen confidence 1.0
“From the TiO2 spectrum, several peaks at 467 cm-1, 1345 cm-1, 1629 cm-1, and 3396 cm-1 can be observed.”
Influence of Sputtering Temperature of TiO2 Deposited onto Reduced Graphene Oxide Nanosheet as Efficient Photoanodes in Dye-Sensitized Solar Cells DOI: 10.3390/molecules25204852 -
Alkyl C-H confidence 1.0
“Peaks at 1459 and 1345 cm-1 are due to the stretching vibration of C-H in CH2 and”
Walnut Oil Oleogels as Milk Fat Replacing System for Commercially Available Chocolate Butter DOI: 10.3390/gels8100613 -
confidence 1.0
“This is also consistent with the AldO cm-1 cm2 4.8 about 100 in the experiments of their Figure Taking identification of a peak at 1345 as being due to in cm3 into account the different reaction volumes (408 in ref 8 experiments in which al”
Roscoe 和 Abbatt - 2005 - Diffuse reflectance FTIR study of the interaction DOI: 10.1021/jp050766r -
Acetate confidence 1.0
“New peaks that emerged at ~765 cm-1 as seen in Polymers2022,14,3019 5of13 Figure 2d, and at ~1345 cm-1 in Figure 2c, are from the O = C-O deformation and the C-H of the formate ion (HCOO-), confirming the incorporation of AFT into the biopo”
Proton-Conducting Biopolymer Electrolytes Based on Carboxymethyl Cellulose Doped with Ammonium Formate DOI: 10.3390/polym14153019 -
Alkyl C-H confidence 1.0
“The broad peaks between 1440 cm-1 and 1390 result from C-H deformation vibration of lipids and cellulose, those between 1375 and cm-1 1345 from the CH bending vibrations in aliphatic groups, while a shoulder or a convolution”
Morphological, Physicochemical and FTIR Spectroscopic Properties of Bee Pollen Loads from Different Botanical Origin DOI: 10.3390/molecules24213974 -
Hydroxyl (O-H) confidence 1.0
“The diffraction patterns of FEN in solid dispersions (C-H stretch aliphatic), 1345 (in-plane O-H bend) and cm-1 were similar to those of the pure drug, suggesting a simple 1111 (C-O stretch), which were consistent in all”
Dissolution study and thermal analysis of fenofibrate–Pluronic F127 solid dispersions DOI: 10.1007/s10973-015-5013-2 -
Chitosan confidence 1.0
“The presence of a band at 1344.95 N(cid:3)(cid:3)H indicates the characteristic bending vibrations of the groups present in chitosan.”
Immobilization of catalase onto chitosan and chitosan–bentonite complex: A comparative study DOI: 10.1016/j.btre.2018.e00258
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