What absorbs at 1696 cm⁻¹ in an FTIR spectrum?
A band near 1696 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 1696 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 |
|---|---|---|---|
| Carbonyl (C=O) | 9 | 7 | 1.0 |
| Carboxyl (COOH) | 8 | 8 | 1.0 |
| Amide | 8 | 8 | 1.0 |
| Methacrylate | 7 | 7 | 1.0 |
| Acetate | 7 | 7 | 1.0 |
| Ketone | 5 | 5 | 1.0 |
| Ester | 5 | 5 | 1.0 |
| Protein beta sheet | 4 | 4 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| Protein | 2 | 2 | 1.0 |
| Hydroxyl (O-H) | 2 | 1 | 1.0 |
| Alkyl C-H | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Aldehyde (CHO) | 1 | 1 | 1.0 |
| Protein alpha helix | 1 | 1 | 1.0 |
| Hydrogen bond | 1 | 0 | 1.0 |
Ranking reflects accumulated literature evidence, not a single fixed rule. Always confirm against your sample context.
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 1696 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
-
Acetate confidence 1.0
“cm-1 (stretching), 3065 due to = C-H (aromatic stretching), 2984 and 2950 due to C-H cm-1 cm-1 (stretching), 1696 due to C=O (stretching vibration), 1615 and 1488 due to C=C cm-1 cm-1 (ring stretching), 1445 due to CH3 (stretching), 1303 an”
Adam 等 - 2022 - Comparative Evaluation of Amlodipine Besylate Gene DOI: 10.14227/DT290422PGC2 -
Carbonyl (C=O) confidence 1.0
“Indomethacin-The FTIR spectrum of indomethacin indicated carbonyl-stretching cm-1 bands at 1696, 1721, and 1724 (Fig.”
Bandi 等 - 2004 - Preparation of budesonideand indomethacin-hydrox DOI: 10.1016/j.ejps.2004.06.007. -
confidence 1.0
“The peak at 1696 represented were mainly attributed to the oxygen-containing functional groups in HA.”
Cheng 等 - 2019 - Extraction of Humic Acid from Lignite by KOH-Hydro DOI: 10.3390/app9071356 -
Acetate confidence 1.0
“measurements for bento-crt showed prominent increasing of cm-1 Results indicated sharp absorption peak at 1696 related to weight loss between 150-800 °C due to the addition of creatine as C-O stretching vibrations of carboxylic acid in crea”
Palladium Nanoparticles on a Creatine‐Modified Bentonite Support: An Efficient and Sustainable Catalyst for Nitroarene Reduction DOI: 10.1002/cplu.201900377 -
Amide confidence 1.0
“cm-1andaminorpeakat1696cm-1denotingantiparallel 12C cm-1 13C cm-1, spectrum indicates a residual amide peak at 1634 and a amide peak at 1616 denoting antiparallel The FP A1/G3 (cid:2)-sheet.”
Gordon 等 - 2004 - Conformational mapping of the N-terminal peptide o DOI: 10.1110/ps.03407704 -
Protein confidence 1.0
“1631 protein solution onto a ZnSe surface and generation of 1657 1677 and 1696 cm-1 cm-1 film a hydrated protein by drying the solution under a Amide I bands close to 1631 and 1696 are β-sheet steady stream of nitrogen.”
Spectroscopic Analysis of Chlamydial Major Outer Membrane Protein in Support of Structure Elucidation: Biophysical characterization of MOMP DOI: 10.1002/pro.3501 -
Aldehyde (CHO) confidence 1.0
“(cm-1) Frequency Band Assignment Species C-H 929 out-of-plane deformation 1018 Ring deformation 1081 Furfural 1156 =C-O-C= ring vibration 1279 1570 C=C stretches 1696 C=O aldehyde stretch 1671 C-O 1163 acid stretch vibration 1369 CH symmetr”
Solubility Temperature Dependence of Bio-Based Levulinic Acid, Furfural, and Hydroxymethylfurfural in Water, Nonpolar, Polar Aprotic and Protic Solvents DOI: 10.3390/pr9060924 -
C c single bond confidence 1.0
“1696.5 and the C-C stretch appears at 1450.2 No characteristic KA peak is seen at 1696.5 cm-1, and the C-C stretch appears at 1450.2 cm-1.”
Formulation and Characterization of Carbopol-934 Based Kojic Acid-Loaded Smart Nanocrystals: A Solubility Enhancement Approach DOI: 10.3390/polym14071489
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