What absorbs at 3330 cm⁻¹ in an FTIR spectrum?
A band near 3330 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 3330 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) | 27 | 25 | 1.0 |
| N h | 13 | 13 | 1.0 |
| Hydrogen bond | 4 | 4 | 1.0 |
| Secondary amine | 4 | 4 | 1.0 |
| Carbohydrate | 4 | 3 | 1.0 |
| Alkyl C-H | 3 | 3 | 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 |
| Water (H2O) | 1 | 1 | 1.0 |
| Lipid | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Ammonium | 1 | 1 | 1.0 |
| Urethane | 1 | 1 | 1.0 |
| N c o | 1 | 1 | 1.0 |
| Amine primary | 1 | 0 | 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 | 3330, 1735, 1650 | Hydroxyl (O-H) | 1 |
| Polyamide | 3330, 1663, 1541 | N h | 1 |
| polysaccharide | 3330, 1637, 1320 | Hydroxyl (O-H), N h | 1 |
| cotton fabric | 3330, 900, 862 | 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 3330 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 2 cm.-1 cm-1 O-H stretching is seen at 3330 The peak at 2937 is observed due to methylene C-H cm-1 stretching at the PAN segments of AVA Np4.”
Synthesis of Aloevera/Acrylonitrile based Nanoparticles for targeted drug delivery of 5-Aminosalicylic acid DOI: 10.1016/j.ijbiomac.2017.08.085 -
Hydroxyl (O-H) confidence 1.0
“The intensity of the OH peak (3330 after uncoated fabrics, activated fabrics, and Se-coated-30.”
Development of Cost-Effective, Ecofriendly Selenium Nanoparticle-Functionalized Cotton Fabric for Antimicrobial and Antibiofilm Activity DOI: 10.3390/fermentation9010018 -
confidence 1.0
“small shoulder peak at ~3360 is tentatively categorized into compared to a major peak at 3330 In previous studies using Group O since this peak is mostly unresolvable due to serious a single-crystal specimen (Kohn et al.”
Nishihara 等 - 2008 - Effect of chemical environment on the hydrogen-rel DOI: 10.2138/am.2008.2653 -
Hydrogen bond confidence 1.0
“1a shows peaks at 3330, 2987, 2903, 1658 and 1598 α-cellulose, corresponding to hydrogen bond stretching of CH and CH of cellulose, C= O 2 cm-1 and C-O of lignin in PCP [19].”
Enhanced arsenic (iii) adsorption from aqueous solution by magnetic pine cone biomass DOI: 10.1016/j.matchemphys.2018.09.067 -
Carbohydrate confidence 1.0
“In addition, Fourier cm-1, transform infra-red (FTIR) analysis of the isolated cellulose showed some peaks at 3330 cm-1, cm-1, cm-1, cm-1 2890 1320 1030 895 corresponding to OH stretching, methylene (-CH 2-) stretching, OH bonding, C-O bond”
Rosdiana 等 - 2020 - Preparation of Silver-Incorporated Rhynchospora co DOI: 10.1088/1757-899X/833/1/012090 -
confidence 1.0
“The amide I band was shifted to a lower wave number (1630 cm-1 instead of 1661 cm-1 for cm-1 brane NE90 peaked at ~ 3330 (N-H and OH stretching), 3100-3000 cm-1 fully aromatic membranes).”
Tang 等 - 2009 - Effect of membrane chemistry and coating layer on DOI: 10.1016/j.desal.2008.04 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Thermal and Physico-Chemical Characteristics of Plaster Reinforced with Wheat Straw for Use as Insulating Materials in Building DOI: 10.3390/buildings12081119 -
Hydrogen bond confidence 1.0
“In the functional group region, the peak at cm-1 approximately 3330 is due to the hydrogen bond O-H stretching.”
Cai 等 - 2022 - Performance of Binderless Board Manufactured Using DOI: 10.15376/biores.17.4.6692-6705
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.