What absorbs at 2969 cm⁻¹ in an FTIR spectrum?
A band near 2969 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 2969 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 | 8 | 8 | 1.0 |
| Hydroxyl (O-H) | 5 | 5 | 1.0 |
| Methyl | 3 | 3 | 1.0 |
| Hydrogen bond | 2 | 2 | 1.0 |
| Carbonyl (C=O) | 2 | 2 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| Methacrylate | 1 | 1 | 1.0 |
| Acetate | 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 |
|---|---|---|---|
| PVC | 2969, 834, 1195 | Alkyl C-H, Hydroxyl (O-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 2969 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
“The C-H stretching band on neighboring CHCl groups at 2969 cm-1 disappeared after the hydrothermally dechlorinated products.”
Understanding Hydrothermal Dechlorination of PVC by Focusing on the Operating Conditions and Hydrochar Characteristics DOI: 10.3390/app7030256 -
Hydroxyl (O-H) confidence 1.0
“This was possible through ITS (internal trancm-1 O-H bonds, while the peaks at 2969 and 2805 belong to the alkane (C-H) bonds;”
Impact of Dragon Fruit Waste in Microbial Fuel Cells to Generate Friendly Electric Energy DOI: 10.3390/su15097316 -
Alkyl C-H confidence 1.0
“Figure 7 shows the co-added FTIR spectra during cm-1 this step and only decomposition products of the PDMS chains are detected: the 2969 band is cm-1 assigned to C-H bond vibration from the methyl moiety of PDMS, 1265 band to C-H bond of cm”
Eugenol-based thermally stable thermosets by Alder-ene reaction: From synthesis to thermal degradation DOI: 10.1002/app.39269. -
Alkyl C-H confidence 1.0
“Additional bands at 2969 and 3430 were associated C-- with C-H stretching and intermolecular O-H bonded to O groups, respectively (Parvinzadeh and Ebrahimi, 2011a).”
Binational survey of personal protective equipment (PPE) pollution driven by the COVID-19 pandemic in coastal environments: Abundance, distribution, and analytical characterization DOI: 10.1016/j.jhazmat.2021.128070 -
Acetate confidence 1.0
“The sharp and well-defined peaks detected cm-1 cm-1 ≈2969 at and 2935 are attributed to -CH3 and -CH2 and have been previously observed in melanoidin samples [43].”
Protein Hydrolysis and Glycosylation as Strategies to Produce Bioactive Ingredients from Unmarketable Prawns DOI: 10.3390/foods10112844 -
Aromatic ring confidence 1.0
“Meanwhile, the bands assigned to PA-5 2969 cm-1 at 3039, 2969 and 2868 are due to aromatic rings 1595”
Liquid phase synthesis of aromatic poly(azomethine)s, their physicochemical properties, and measurement of ex situ electrical conductivity of pelletized powdered samples DOI: 10.1080/15685551.2016.1231042 -
Hydroxyl (O-H) confidence 1.0
“The peak at 2968.79 is stretching cm-1 for O-H.”
Biodegradation of Azo Dye Methyl Red by Pseudomonas aeruginosa: Optimization of Process Conditions DOI: 10.3390/ijerph19169962 -
Alkyl C-H confidence 1.0
“The FTIR spectrum of the control membrane (Figure 5) Comparing to the controle membrane, the Tg of PSf/MC displayed the characteristics absorption peaks of all the bonds, cm-1 membranes is slightly lower, this may be due to the presence in”
Nadour 等 - 2017 - Effects of Methylcellulose on the Properties and M DOI: 10.1590/1980-5373-MR-2016-0544
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