What absorbs at 2943 cm⁻¹ in an FTIR spectrum?
A band near 2943 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 2943 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 | 20 | 20 | 1.0 |
| Hydroxyl (O-H) | 3 | 3 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| Methyl | 2 | 2 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Acetate | 1 | 1 | 1.0 |
| N n bond | 1 | 1 | 1.0 |
| Alkene (C=C) | 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 |
|---|---|---|---|
| PVP | 2943, 2983, 1648 | Alkyl C-H, Hydroxyl (O-H) | 1 |
| PCL | 2943, 1751, 1724 | Alkyl C-H, Methoxy (OCH3), Hydroxyl (O-H) | 1 |
| polycaprolactone | 2943, 1580, 1751 | Methoxy (OCH3), 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 2943 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
“aliphatic CH stretching was observed as two peaks at 2943, and 2885 In addition, the FTIR Aloufi,A.S.;Sonbol,H.;Korany,S.M.”
Bio_Fabricated Levan Polymer from Bacillus subtilis MZ292983.1 with Antibacterial, Antibiofilm, and Burn Healing Properties DOI: 10.3390/app12136413 -
Alkyl C-H confidence 1.0
“with poly(vinyl alcohol) with the O-H stretching of alcohol at 3387 The 177 cm-1 vibrational band at 2943 refers to the C-H stretching of alkyl groups, including 178”
Synthesis of lanthanum tungstate interconnecting nanoparticles by high voltage electrospinning DOI: 10.1016/j.apsusc.2015.05.194 -
Alkyl C-H confidence 1.0
“FTIR spectra of the enzyme-treated plastic film revealed structural cm-1 that corresponded changes in the chemical composition, indicating a specific peak at 2943 C-H to alkenyl stretch.”
Lignin peroxidase isoenzyme: a novel approach to biodegrade the toxic synthetic polymer waste DOI: 10.1080/09593330.2017.1422550 -
N n bond confidence 1.0
“The peaks at 2943 and 2873 arise from the IEC N N W = ( - ) (3) E (meq g) o,HCl ,HCl dry -CH -CH -CH stretching of 3, 2, and groups.”
Fabricating hydroxyl anion conducting membranes based on poly(vinyl alcohol) and bis(2-chloroethyl) ether-1,3-bis[3-(dimethylamino)propyl] urea copolymer with linear anion-exchange sites for polymer electrolyte membrane fuel cell DOI: 10.1016/j.ssi.2017.06.003 -
Alkyl C-H confidence 1.0
“In conjunction, four overlapping signals can be applied to the (CH) stretching cm-1, modes: symmetrical CH stretching at approximately 2885 asymmetri2 cm-1 cm-1 cal CH stretching at approximately 2943 [16, 17], peaks at 1446 2”
Experimental and DFT studies on the structural and optical properties of chitosan/polyvinyl pyrrolidone/ZnS nanocomposites DOI: 10.1007/s00289-023-04700-0 -
Alkyl C-H confidence 1.0
“2970 0.9129 C H - C - C H bending 952 0.9222 3 3 C - H Methanol stretching 2943”
Assessment of quality of commercial hand sanitizers using Fourier transform infrared spectroscopy and gas chromatography DOI: 10.1016/j.mex.2023.102274 -
Alkyl C-H confidence 1.0
“LLM confirmed rule peak-group candidate”
Preparation of electrospun polycaprolactone nanofiber mats loaded with microalgal extracts DOI: 10.1002/elsc.201900009 -
Alkyl C-H confidence 1.0
“LLM confirmed rule peak-group candidate”
Development and characterization of natural sourced bioplastic for food packaging applications DOI: 10.1016/j.heliyon.2023.e13538
Have a spectrum with this band?
Upload your FTIR spectrum and get a full interpretation report — peak assignments with literature citations, library matches, and a literature-backed analysis — in seconds.