What absorbs at 1708 cm⁻¹ in an FTIR spectrum?
A band near 1708 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 1708 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) | 28 | 25 | 1.0 |
| Ester | 14 | 14 | 1.0 |
| Carboxyl (COOH) | 14 | 12 | 1.0 |
| Methacrylate | 12 | 12 | 1.0 |
| Acetate | 12 | 12 | 1.0 |
| Amide | 11 | 11 | 1.0 |
| Ketone | 10 | 10 | 1.0 |
| Alkyl C-H | 5 | 5 | 1.0 |
| Fatty acid | 3 | 3 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| Aromatic ring | 2 | 2 | 1.0 |
| Alkene (C=C) | 2 | 2 | 1.0 |
| Urethane | 2 | 1 | 1.0 |
| Triglyceride | 2 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Lipid | 1 | 1 | 1.0 |
| Oxygen heterocycle | 1 | 1 | 1.0 |
| N-O bond | 1 | 1 | 1.0 |
| Nucleic acid | 1 | 1 | 1.0 |
| Methyl | 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 |
|---|---|---|---|
| polyester | 1708, 1700, 1250 | Carbonyl (C=O), Methacrylate, Ester | 1 |
| DNA | 1708, 1712, 1660 | 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 1708 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
“The oxirane ring cm-1, signal can be detected at 845 while carboxylic acid carbonyl functional groups (C=O) cm-1, absorption bands of OA and EOA are denoted by peaks at 1708 and 1703 respectively,”
Bahadi 等 - 2021 - Synthesis and Characterization of Green Biodegrada DOI: 10.33263/BRIAC116.1435914371 -
Carboxyl (COOH) confidence 1.0
“Characterization analysis OA and EOA FTIR spectra was used to comparatively analyze OA and EOA structures, the oxirane ring signal can be detected at cm-1 845 while carboxylic acid carbonyl functional groups (C=O) absorption bands of OA and”
Bahadi 等 - 2021 - Synthesis and characterization of palm oleic acid DOI: 10.48317/IMIST.PRSM/morjchem-v9i3.23865 -
Fatty acid confidence 1.0
“For free fatty acid (FFA) quantification, C=O cm-1 the band at 1708 was used, corresponding to the carboxylic acid, whereas for fatty acid cm-1 C=O methyl ester (FAME) quantification, the peak corresponding to at 1746 was considered, which”
Monitoring Enzymatic Hydroesterification of Low-Cost Feedstocks by Fourier Transform InfraRed Spectroscopy DOI: 10.3390/catal9060535 -
Alkyl C-H confidence 1.0
“The bands observed at 2933 and 2863 are respectively related to the C-H vibrationsandtheC-Hstretchinginmethoxygroups.Thebandat1708cm(cid:2)1isassignedto unconjugated C¼O stretching.”
Synthesis and characterization of lignin–melamine–formaldehyde resin DOI: 10.1177/0892705716632856 -
Acetate confidence 1.0
“A similar result was obtained by Mello and Vidal [27], who suggested that FTIR spectra cm-1, 1708 and 1668 cm-1 in the region (1700-1600 cm-1) could be due to C=O stretching vibration of of bovine DNA was higher than that of fish DNA at the”
Han 等 - 2018 - Insight into Rapid DNA-Specific Identification of DOI: 10.3390/molecules23112842 -
confidence 1.0
“The band at 1708 is attributed to the cm-1) (1630-1780 veals that synthesized NPs have Fe presence of carbonyl groups 3O crystals with JCPDS and organic 4 cm-1).”
Removal of Cr(VI) by magnetic iron oxide nanoparticles synthesized from extracellular polymeric substances of chromium resistant acid-tolerant bacterium Lysinibacillus sphaericus RTA-01 DOI: 10.1007/s40201-019-00415-5 -
Carbonyl (C=O) confidence 1.0
“Determination of Propamocarb in agrochemicals 1708cm-1 The band located at was chosen because in this region the carbonyl band is not overlapped with any other band A set of commercially formulated pesticides, obtained from in the sample ma”
Quintas 等 - 2008 - Towards minimization of chlorinated solvents consu DOI: 10.1016/j.talanta.2007.11.017 -
Alkene (C=C) confidence 1.0
“Furthermore, the absorption peak at 1707.86 cm-1 indicated the C=O stretchrevealed the C=C stretching of alkenes.”
Facile Green Synthesis of Zinc Oxide Nanoparticles with Potential Synergistic Activity with Common Antifungal Agents against Multidrug-Resistant Candidal Strains DOI: 10.3390/cryst12060774
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