What absorbs at 3900 cm⁻¹ in an FTIR spectrum?
A band near 3900 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 4 cited sources
Possible functional-group assignments
| Functional group | Supporting facts | Cited sources | Top confidence |
|---|---|---|---|
| Hydroxyl (O-H) | 4 | 3 | 1.0 |
| Alkyl C-H | 2 | 2 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| Acetate | 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 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Silanol (Si-OH) | 1 | 0 | 1.0 |
| Silicon (Si) | 1 | 0 | 1.0 |
Ranking reflects accumulated literature evidence, not a single authoritative rule. Always confirm against your sample context.
Literature behind these assignments
-
Hydroxyl (O-H) confidence 1.0
“OH band C-O stretching 3900 3400 2900 2400”
Electrochemical and Ion Transport Studies of Li+ Ion-Conducting MC-Based Biopolymer Blend Electrolytes DOI: 10.3390/ijms23169152 -
Hydroxyl (O-H) confidence 1.0
“Peaks at 3915 and cm-1 3900 correspond to an O-H stretching vibration, indicating the presence of an alcohol group, while the”
Nematicidal activity of seaweed-synthesized silver nanoparticles and extracts against Meloidogyne incognita on tomato plants DOI: 10.1038/s41598-022-06600-1 -
Acetate confidence 1.0
“The interactions that occur can cause a shift in the polymer C=C and C=O bands C-H rocking band 3900 3400 2900 2400 1900 1400 900 400 (cm-1) Wavenumber”
Innovative Green Chemistry Approach to Synthesis of Sn2+-Metal Complex and Design of Polymer Composites with Small Optical Band Gaps DOI: 10.3390/molecules27061965 -
Alkyl C-H confidence 1.0
“C-H rocking band OH band (%) Transmittance 3900 3400”
Polymer Composites with 0.98 Transparencies and Small Optical Energy Band Gap Using a Promising Green Methodology: Structural and Optical Properties DOI: 10.3390/polym13101648
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