What absorbs at 1700 cm⁻¹ in an FTIR spectrum?
A band near 1700 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 1700 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) | 168 | 141 | 1.0 |
| Amide | 117 | 107 | 1.0 |
| Carboxyl (COOH) | 94 | 84 | 1.0 |
| Methacrylate | 75 | 69 | 1.0 |
| Acetate | 75 | 69 | 1.0 |
| Ester | 69 | 64 | 1.0 |
| Ketone | 64 | 60 | 1.0 |
| Alkyl C-H | 21 | 17 | 1.0 |
| Hydroxyl (O-H) | 16 | 15 | 1.0 |
| C-O single bond | 15 | 13 | 1.0 |
| Methoxy (OCH3) | 14 | 12 | 1.0 |
| Alkene (C=C) | 12 | 11 | 1.0 |
| Carbohydrate | 10 | 9 | 1.0 |
| Urethane | 10 | 8 | 1.0 |
| Aromatic ring | 9 | 8 | 1.0 |
| N h | 9 | 8 | 1.0 |
| N-O bond | 8 | 8 | 1.0 |
| Protein | 7 | 7 | 1.0 |
| Hydrogen bond | 7 | 6 | 1.0 |
| Ring structure | 6 | 6 | 1.0 |
| S eq o | 5 | 5 | 1.0 |
| C c single bond | 5 | 4 | 1.0 |
| Water (H2O) | 4 | 4 | 1.0 |
| Aldehyde (CHO) | 4 | 3 | 1.0 |
| Imide | 3 | 3 | 1.0 |
| Secondary amine | 2 | 2 | 1.0 |
| C n single bond | 2 | 2 | 1.0 |
| Lipid | 2 | 2 | 1.0 |
| Nucleic acid | 2 | 2 | 1.0 |
| Phosphate (PO4) | 2 | 2 | 1.0 |
| C=n | 2 | 2 | 1.0 |
| Protein beta sheet | 2 | 2 | 1.0 |
| Methyl | 1 | 1 | 1.0 |
| Quinone | 1 | 1 | 1.0 |
| Acetyl | 1 | 1 | 1.0 |
| N c o | 1 | 1 | 1.0 |
| Urea | 1 | 1 | 1.0 |
| Phosphorus | 1 | 1 | 1.0 |
| Lewis acid site | 1 | 1 | 1.0 |
| Amino acid | 1 | 1 | 1.0 |
| Oxygen heterocycle | 1 | 1 | 1.0 |
| Oxalate | 1 | 1 | 0.9 |
| Fluorine (C-F) | 1 | 0 | 1.0 |
| Nitrate | 1 | 0 | 0.7 |
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 |
|---|---|---|---|
| polyester | 1700, 1250, 1720 | Carbonyl (C=O), Methacrylate, Amide | 1 |
| silver nanoparticles | 1700, 1636, 1631 | Methacrylate, Amide | 1 |
| honey | 1700, 2005, 1199 | Methacrylate, Amide | 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 1700 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
-
Carboxyl (COOH) confidence 1.0
“It is rather interesting to detect a carboxyl group's peak (C=O) at 1700 cm-1, associated with an oleic acid epoxide, apparently decreased after polymerization.”
Bahadi 等 - 2021 - Synthesis and Characterization of Green Biodegrada DOI: 10.33263/BRIAC116.1435914371 -
confidence 1.0
“1700cm-1, and N-H bond stretching peak appeared from 4.”
Bawazeer 等 - 2022 - Biogenic Synthesis of Silver Nanoparticles Using R DOI: 10.1155/2022/7365931 -
Carbohydrate confidence 1.0
“LLM confirmed rule peak-group candidate”
Can 等 - 2023 - Choline Chloride-Based Deep Eutectic Solvent-Treat DOI: 10.3390/f14030569 -
Carbonyl (C=O) confidence 1.0
“confirmed significant protective of NaCl could be by FTIR-ATR to any large extent during the aging and no where the previously discussed peak shifts were not as profound degradation could be observed, there is a clear increase in the cm-1 a”
Carlsson 等 - 2013 - A Comparative Study of the Effects of Rinsing and DOI: 10.1021/jp3125582 -
Amide confidence 1.0
“The peak amounts (Gallardo-Velazquez, Osorio-Revilla, Loa, & 1547cm(cid:3)1 resulted from N-H bending and observed at Rivera-Espinoza, 2009) The band which varied between 1700cm(cid:3)1 C-N stretching vibrations of Amide II (Coates, 2000;”
Cebi 等 - 2020 - An evaluation of FTIR spectroscopy for prediction DOI: 10.1080/00218839.2019.1707009 -
Acetate confidence 1.0
“All spectra are cm-1, characterized by a major band centred at 1725 ascribed to the cm-1, free C O urethane groups, and another peak at about 1700”
Hydrogen bonding and thermomechanical properties of model polydimethylsiloxane based poly(urethane-urea) copolymers: Effect of hard segment content DOI: 10.1016/j.porgcoat.2015.06.015 -
Ring structure confidence 1.0
“carbonyls.20,62 observed between the D-ring peaks at 1700 and 1710 This is red-shift the vibrational frequency of The two peaks”
Chenchiliyan 等 - 2023 - Ground-state heterogeneity and vibrational energy DOI: 10.1063/5.0135268 -
Carbonyl (C=O) confidence 1.0
“The characteristic peak of FA could be seen around 1700 cm-1, which was due to the absorbance of the carbonyl group.”
Formation of Intermediate Amylose Rice Starch–Lipid Complex Assisted by Ultrasonication DOI: 10.3390/foods11162430
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