What absorbs at 3338 cm⁻¹ in an FTIR spectrum?
A band near 3338 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 3338 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 |
|---|---|---|---|
| Hydroxyl (O-H) | 10 | 10 | 1.0 |
| Alkyl C-H | 4 | 4 | 1.0 |
| N h | 2 | 2 | 1.0 |
| Hydrogen bond | 1 | 1 | 1.0 |
| Carbohydrate | 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 |
|---|---|---|---|
| PET | 3338, 1408, 800 | Alkyl C-H, N h | 1 |
| starch | 3338, 1650, 1540 | Hydroxyl (O-H), Alkyl C-H | 1 |
| Nanotubes | 3338, 1735, 1630 | Alkyl C-H, Hydroxyl (O-H) | 1 |
| graphene oxide | 3338, 1150, 3400 | Hydroxyl (O-H), Alkyl C-H | 1 |
| bamboo | 3338, 1737, 1731 | 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 3338 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
-
Hydroxyl (O-H) confidence 1.0
“The cm-1 peak intensity of the transmittance band at approximately 3338 was assigned to the O-H stretching vibration, which drastically decreased after the 4-methylcatecol treatment.”
Liew 等 - 2016 - 4-Methylcatechol-treated Jute-Bamboo Hybrid Compos DOI: 10.1016/j.carbpol.2003.11.015 -
confidence 1.0
“cm1 The FT-IR analysis of the PET akes gives an indication of N-H stretching at 3338.04 and”
Odigbo 等 - 2023 - Polyethylene terephthalate (PET) biodegradation by DOI: 10.21203/rs.3.rs-2044624/v1 -
Hydroxyl (O-H) confidence 1.0
“Modified starch exhibited absorption peaks at 3338, 2925, and 1743 Journal which assigned to the stretching vibrations of poly -OH and -CH 2, deformation of -”
Ratnaningsih 等 - 2020 - Physicochemical properties, in vitro starch digest DOI: 10.1016/j.ijbiomac.2019.09.092 -
Hydroxyl (O-H) confidence 1.0
“3a, the bands cm-1 at 3347 assigned as -OH stretching vibration is shifted to lower wavenumbers 3338 cm-1.”
Bian 等 - 2021 - Crystalline Structure Analysis of All-cellulose Na DOI: 10.1007/s10570-017-1259-0 -
Hydroxyl (O-H) confidence 1.0
“cm-1 The bands widened between 3500 and 3252 referring to the striation band The bands widened between 3500 and 3252 cm-1 referring to the striation band of the cm-1, of the group (OH), mainly O-H stretching bands at 3338 C-H vibrations nea”
Rutin-Functionalized Multi-Walled Carbon Nanotubes: Molecular Docking, Physicochemistry and Cytotoxicity in Fibroblasts DOI: 10.3390/toxics9080173 -
Alkyl C-H confidence 1.0
“In the GO spectrum, one could observe a large absorption band with three peaks at In the GO spectrum, one could observe a large absorption band with three peaks at cm-1 cm-1 3338 and 3197 assigned to the stretching vibration of the C-H and”
Synthesis and Characterization of Some Graphene Oxide Powders Used as Additives in Hydraulic Mortars DOI: 10.3390/app112311330 -
Hydroxyl (O-H) confidence 1.0
“As depicted in Figure 2, the broad peak at 3338 cm-1 which appears in both spectra is attributed to the O-H frequency, whereas the peaks at 2898 and cm-1”
Razak 等 - 2014 - The Influence of Chemical Surface Modification of DOI: 10.3390/molecules19032957 -
confidence 1.0
“In pure aniline (ANI) solution, the FTIR peaks at 3338 and cm-1 N-H C Generally, there is a decrease in absorbance and wave1635 are due to the stretching vibrations and”
Regasa 等 - 2020 - Development of Molecularly Imprinted Conducting Po DOI: 10.1021/acsomega.9b03747
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