What absorbs at 1703 cm⁻¹ in an FTIR spectrum?
A band near 1703 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 1703 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) | 11 | 11 | 1.0 |
| Methacrylate | 5 | 5 | 1.0 |
| Ester | 5 | 5 | 1.0 |
| Carboxyl (COOH) | 5 | 5 | 1.0 |
| Acetate | 5 | 5 | 1.0 |
| Ketone | 4 | 4 | 1.0 |
| Amide | 4 | 4 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| Aromatic ring | 2 | 2 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Alkyl C-H | 1 | 1 | 1.0 |
| Imide | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| Urea | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 0.9 |
| Urethane | 1 | 1 | 0.9 |
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 |
|---|---|---|---|
| polyurethane | 1703, 2270, 1700 | Methacrylate, Carbonyl (C=O) | 2 |
| coal | 1703, 1600, 3030 | Carboxyl (COOH), Methacrylate | 1 |
| composite | 1703, 1295, 2922 | 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 1703 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 FTIR S.-Y.Linetal./JournalofPharmaceuticalandBiomedicalAnalysis53 (2010) 799-803 801 spectrumofintactLORisalsodisplayedinFig.2.SeveralcharacteristicIRabsorptionbandsandtheirassignmentsofLORareshownas 1703cm-1 1474cm-1 follows: (C O of e”
Curve-fitting FTIR studies of loratadine/hydroxypropyl-β-cyclodextrin inclusion complex induced by co-grinding process DOI: 10.1016/j.jpba.2010.06.010 -
Ester confidence 1.0
“Procorresponding to the band of the ester carbonyl group at posals for molecular ion composition were made by exact 1755.14cm-1 1703.06cm-1”
Danciu 等 - 2015 - Preliminary In Vitro Evaluation of Genistein Chemo DOI: 10.1155/2015/262930 -
Acetate confidence 1.0
“The main differences aromaticity index usually observed for soil were: a shift of the band of C=O stretching from 1703 to Conclusion cm-1 1713 and of the band of C=C stretching from 1603 to cm-1.”
Dick 等 - 2017 - Impact of HNO3 Solution Treatment of South Brazil DOI: 10.21577/0103-5053.20160230 -
Urea confidence 1.0
“cm-1 The bands at 1703 (C=O of urethane) and Figure 4A shows the FTIR spectra of CNW, and cm-1 1622 (C = O of urea) (RATH et al., 2008;”
Haraguchi 等 - 2013 - Glycerol-derived polyurethane nanocomposites conta DOI: 10.4025/actascitechnol.v35i4.20276 -
Carboxyl (COOH) confidence 1.0
“6 of 11 cm-1 Polymers 2017, 9, 163 6 of 11 The characteristic band at 1730 and 1703 was identified as a twin peak indicating the presence cm-1 characteristic band at 1730 and 1703 cm-1 was identified as a twin peak indicating the presence o”
Manufacturing and Characterization of Novel Electrospun Composite Comprising Polyurethane and Mustard Oil Scaffold with Enhanced Blood Compatibility DOI: 10.3390/polym9050163 -
Carbonyl (C=O) confidence 1.0
“On the shorter wavelength cm-1 side, this band is enhanced with the maximum at ~1703 corresponding to the vibrations of another carbonyl group, this one present primarily in acid groups.”
Comparative Analysis of Phytochemicals and Antioxidant Properties of Borage Oil (Borago officinalis L.) and Milk Thistle (Silybum marianum Gaertn) DOI: 10.3390/app13042560 -
Acetate confidence 1.0
“(>NH C=O stretching of the ionized amine ) at 2689-2463 the stretching in COOH and characteristic bands can be assigned to the O-H stretching in COOH at 3530-3373 cm-1, the N-H stretching of the ionized amine (>NH2+) at 2689-2463 cm-1, the”
Kowalczuk - 2020 - FTIR Characterization of the Development of Antimi DOI: 10.3390/coatings10090818 -
Carbonyl (C=O) confidence 1.0
“Assigned to C=O bond of carboxylic acid moiety.”
A Mechanism for the Adsorption of 2-(Hexadecanoylamino)Acetic Acid by Smithsonite: Surface Spectroscopy and Microflotation Experiments DOI: 10.3390/min9010015
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