What absorbs at 1704 cm⁻¹ in an FTIR spectrum?
A band near 1704 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 1704 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) | 20 | 15 | 1.0 |
| Carboxyl (COOH) | 14 | 13 | 1.0 |
| Amide | 14 | 11 | 1.0 |
| Methacrylate | 12 | 11 | 1.0 |
| Ester | 12 | 11 | 1.0 |
| Acetate | 12 | 11 | 1.0 |
| Ketone | 11 | 10 | 1.0 |
| Alkene (C=C) | 3 | 3 | 1.0 |
| Urethane | 2 | 2 | 1.0 |
| Metal oxygen | 2 | 1 | 0.9 |
| Hydrogen bond | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| C-O single bond | 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 |
|---|---|---|---|
| polyurethane | 1704, 2270, 1700 | Methacrylate, Carbonyl (C=O), Amide | 1 |
| biodiesel | 1704, 858, 3470 | Carbonyl (C=O), Methacrylate | 1 |
| gold nanoparticles | 1704, 1638, 3252 | Amide, Methacrylate, Carbonyl (C=O) | 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 1704 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 absorption peak at 1704 representing the -C=O stretching vibration of the spheres attached ICPDR (ICPDRSS) indicates the formation of the urethane bond.”
Kang - 2014 - Concentration effect on the optical absorption and DOI: 10.1117/12.2061447 -
Acetate confidence 1.0
“The absorption peak at 1704 form and has a geometry with phenyl rings twisted perrepresents a -C=O stretching vibration for the urethane pendicular to the plane determined by the C-N=N-C cm-1 are bond.”
Kim 和 Kang - 2014 - The cause of absorption and luminescence band shif DOI: 10.3938/jkps.64.451 -
Ester confidence 1.0
“treatment with LPS (1 Generally, LPS induces inflammation to the cells which were assigned to saturated ester C=O The two major peaks at 1749 and 1704 cm-1 causes cell rupture, cell clumps, and necrosis that were understood by the cell viab”
Adnan 等 - 2022 - Microwave-Assisted Synchronous Nanogold Synthesis DOI: 10.3390/ph15020111 -
Carboxyl (COOH) confidence 1.0
“FTIR stretching vibrations, acid), 1728 and 1704 cm-1): cm-1 (CO (4000-500 cm-1 (S-S disulfide νS-S).”
Printing “Smart” Inks of Redox-Responsive Organometallic Polymers on Microelectrode Arrays for Molecular Sensing DOI: 10.1021/acsami.9b11927 -
C-O single bond confidence 1.0
“Likewise, a high correspondence can be observed between the SERS spectra of GA and cm-1 TA (Figure 5b,d), the main difference being the existence of a medium band at 1704 ν(C-O) attributed to the ester vibration, which seems to be absent in”
Vibrational Study (Raman, SERS, and IR) of Plant Gallnut Polyphenols Related to the Fabrication of Iron Gall Inks DOI: 10.3390/molecules27010279 -
Carbonyl (C=O) confidence 1.0
“According to the results, the Fourier-transform infrared spectroscopy FTIR spectra cm-1 cm-1) and 1742 and C-O showed characteristic absorption of esters, the C=O bond stretches (1704 cm-1 cm1).”
Ferreira da Silva Neto 等 - 2021 - DOI: 10.18273/revion.v34n2-2021009 -
Amide confidence 1.0
“In this urethane carbonyl being detected at 1704 The C-N stretching bands, combined with those of spectrum, the -CH2stretching bands (from PPG) are observed between 2927 and 2854 cm-1, the band cm-1 cm-1, spectrum, the -CH2stretching bands”
Gregori Valdes 等 - 2018 - Synthesis and Characterization of Isosorbide-Based DOI: 10.3390/polym10101170 -
Carbonyl (C=O) confidence 1.0
“LLM confirmed rule peak-group candidate”
Effect of Phenolic Resin Oligomer Motion Ability on Energy Dissipation of Poly (Butyl Methacrylate)/Phenolic Resins Composites DOI: 10.3390/polym12020490
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