What absorbs at 1702 cm⁻¹ in an FTIR spectrum?
A band near 1702 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 1702 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) | 13 | 12 | 1.0 |
| Methacrylate | 8 | 8 | 1.0 |
| Acetate | 8 | 8 | 1.0 |
| Carboxyl (COOH) | 8 | 7 | 1.0 |
| Amide | 6 | 6 | 1.0 |
| Ketone | 5 | 5 | 1.0 |
| Ester | 5 | 5 | 1.0 |
| Alkyl C-H | 3 | 3 | 1.0 |
| Methoxy (OCH3) | 3 | 3 | 1.0 |
| C-O single bond | 3 | 3 | 1.0 |
| Imide | 3 | 2 | 1.0 |
| Protein beta turn | 1 | 1 | 1.0 |
| Protein beta sheet | 1 | 1 | 1.0 |
| C=n | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
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 |
|---|---|---|---|
| Starch | 1702, 1650, 1540 | Methacrylate, Acetate | 1 |
| cellulose | 1702, 1735, 1650 | Acetate, Methacrylate | 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 1702 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
“The spectrum of commercial PHB - 1 = Pure strain of Bacillus cereus on agar slant was obtained from the showed peaks for C O stretching at 1702.048 cm aliphatic stretchDepartment of Microbiology, Federal University of Technology, Akure.”
Recycling of used polyethylene through solvent blending of plasticized polyhydroxybutyrate and its degradation potential DOI: 10.1016/j.jcomc.2020.100021 -
Acetate confidence 1.0
“cm-1 The peak at 1702 is referred to the stretching vibrations of the C-O groups in sorbitol (Figure”
Cellulose‐reinforced starch biocomposite: optimization of the effects of filler and various plasticizers using Design‐Expert method DOI: 10.1002/star.202000028. -
Hydroxyl (O-H) confidence 1.0
“The peak observed at in raw the binding of dye as well as the increased surface area of HAB indicated the presence of -OH groups and the peak sorbent by increasing dosage amount [50] and also, on the 1597.84cm-1 1702.44cm-1 area observed be”
Akram 等 - 2021 - Kinetic and Isothermal Investigations of Cost-Effe DOI: 10.1155/2021/5549536 -
Carboxyl (COOH) confidence 1.0
“= ylic acid at the carboxylic acid peaks (C O 1742 and 1702 cm-1).”
Insights into ultrasound-promoted degradation of naphthenic acid compounds in oil sands process affected water. Part I: Accelerated H-abstraction and decarboxylation of aromatic and alicyclic compounds DOI: 10.1016/j.ultsonch.2022.105929 -
Acetate confidence 1.0
“A band at 1702 cm-1 was asassigned to the C=O vibration of nucleic bases [23].”
Detection of Human Cholangiocarcinoma Markers in Serum Using Infrared Spectroscopy DOI: 10.3390/cancers13205109 -
Imide confidence 1.0
“5 compares FT-IR spectra of PNTCDA composite electrode at differentstates.ThepristinePNTCDAcompositeelectrodeshowsthe cm-1, cm-1 characteristic absorption bands - namely, 1702 1668 and cm-1 ν C=O), ν C=O), δ 770 corresponding to (imide (imi”
Chen 等 - 2015 - Aqueous Lithium-Ion Batteries Using O-2 Self-Elimi DOI: 10.1149/2.0101510jes -
Carbonyl (C=O) confidence 1.0
“LLM confirmed rule peak-group candidate”
Jadhav 等 - 2016 - Synthesis of poly(N-isopropylacrylamide) by distil DOI: 10.1002/app.44181 -
Carbonyl (C=O) confidence 1.0
“The copolymer-grafted particles (lower spectrum in inset cm-1 zoomed area) showed peaks at 1702, 1668, 1551, 1460 due to MPS carbonyl, secondary amide carbonyl, secondary amide -N-H bending and C-H asymmetric bending of the”
Jadhav 等 - 2017 - Thermoresponsive copolymer-grafted SBA-15 porous s DOI: 10.3144/expresspolymlett.2017.11
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