What absorbs at 2345 cm⁻¹ in an FTIR spectrum?
A band near 2345 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 2345 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 |
|---|---|---|---|
| Carbon dioxide | 5 | 4 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| Alkyl C-H | 2 | 2 | 1.0 |
| C#c | 2 | 2 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| Adsorbed carbon monoxide | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Thiol | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Nitrile | 1 | 1 | 0.8 |
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 | 2345, 1735, 1650 | Alkyl C-H, Acetate, Methacrylate | 1 |
| hemicellulose | 2345, 1730, 897 | Alkyl C-H, Methacrylate, Acetate | 1 |
| nanotubes | 2345, 1735, 1630 | Alkyl C-H, Methacrylate, Acetate | 1 |
| Glycerol | 2345, 1585, 1630 | Methacrylate, Acetate, Alkyl C-H | 1 |
| hydroxyapatite | 2345, 1620, 1639 | Alkyl C-H, Methacrylate, Acetate | 1 |
| CaCO3 | 2345, 1141, 712 | Alkyl C-H | 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 2345 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
-
Carbohydrate confidence 1.0
“The CdS NPs synthesized by using D-glucose and EPS cm-1, showed peak at 2345.15 which also confirmed the presence of -SH group.”
Extracellular polymeric substances of a marine bacterium mediated synthesis of CdS nanoparticles for removal of cadmium from aqueous solution DOI: 10.1016/j.jcis.2015.10.004 -
Carbon dioxide confidence 1.0
“Typical characteristic bands corresponding to the carbonate groups of the CaCO3 component of hydroxyapatite are located around 1411cm(cid:3)1and1465cm(cid:3)1.Thesinteredsamplesshowedsmallfrequencybandsaround2345cm(cid:3)1and cm(cid:3)1 235”
Experimental data on the characterization of hydroxyapatite synthesized from biowastes DOI: 10.1016/j.dib.2019.104485 -
C#c confidence 1.0
“cm-1 C≡C Moreover, the sharp peaks at 2345 and 2227 cm-1 indicated C≡C stretching vibrations, and the same vibration.”
Basheer 等 - 2020 - Synthesis, Characterization, and Analysis of Hybri DOI: 10.3390/polym12061305 -
Thiol confidence 1.0
“Again, other minor peaks at 2345 cm(cid:0) cm(cid:0) 1, 1 S-H C-O 1340 and 1165 are for vibration of cysteine, CH2 side chain vibrations of collagen, and stretching vibration of of”
Hossain 和 Roy - 2023 - Monitoring the curing efficiency of a plant-based DOI: 10.1016/j.heliyon.2023.e16273 -
Carbon dioxide confidence 1.0
“LLM confirmed rule peak-group candidate”
Marie 等 - 2012 - PEM Anchorage on Titanium Using Catechol Grafting DOI: 10.1371/journal.pone.0050326 -
Alkyl C-H confidence 1.0
“At 2345 cm-1 the band referring to the alkyl chain denotes the cm-1 constituent of cellulose [56].”
Periquiteira (Cochlospermum orinocense): A Promising Amazon Fiber for Application in Composite Materials DOI: 10.3390/polym15092120 -
Adsorbed carbon monoxide confidence 1.0
“Moreover, cm-1 the concomitant presence of the band in 2345 with the ν(CO) stretching mode at high potentials support the ability of Pt(111) to oxidize glycerol to CO from adsorbed CO, but to a 2 lesser extent than observed in acidic media”
Sandrini 等 - 2018 - Mechanistic aspects of glycerol electrooxidation o DOI: 10.1016/j.elecom.2017.11.027 -
Carbon dioxide confidence 1.0
“cm-1 In Figure 4a (oxidation) a sharp band at 2345 corresponding to the formation of CO 2 arises at 0.8 V and increases abruptly at higher potentials.”
Taleb 等 - 2014 - Electrochemical and In Situ FTIR Study of o-Cresol DOI: 10.1007/s12678-013-0182-x.
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