What absorbs at 1706 cm⁻¹ in an FTIR spectrum?
A band near 1706 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 1706 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) | 16 | 11 | 1.0 |
| Carboxyl (COOH) | 14 | 10 | 1.0 |
| Ester | 11 | 7 | 1.0 |
| Methacrylate | 10 | 6 | 1.0 |
| Acetate | 10 | 6 | 1.0 |
| Ketone | 9 | 5 | 1.0 |
| Amide | 9 | 5 | 1.0 |
| Fatty acid | 2 | 2 | 1.0 |
| N-O bond | 2 | 2 | 1.0 |
| Alkyl C-H | 2 | 2 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Lignin | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Methoxy (OCH3) | 1 | 1 | 1.0 |
| C-O single bond | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| Hydrogen bond | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
| Amino acid | 1 | 1 | 0.8 |
| Methyl | 1 | 1 | 0.8 |
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 |
|---|---|---|---|
| polypyrrole | 1706, 1700, 400 | 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 1706 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
-
Carbonyl (C=O) confidence 1.0
“cm-1 Pure TA spectra displayed an infrared absorption band at 3398 related to the cm-1 hydrogen-bonded hydroxyl stretching vibration, at 1706 associated with stretching vibration of the carbonyl group (in the aliphatic ester bonds).”
Chitosan-Coated PLGA Nanoparticles Encapsulating Triamcinolone Acetonide as a Potential Candidate for Sustained Ocular Drug Delivery DOI: 10.3390/pharmaceutics13101590 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Structural, spectral and nonlinear optical analysis of Bis(2-methyllactato)borate tetrahydrate: a new nonlinear optical crystal for laser applications DOI: 10.1016/j.ijleo.2020.164384 -
Carboxyl (COOH) confidence 1.0
“cm-1, aromatic-CH attributed to in plane band at 1230 cm-1 deformation, with the band at 1706 attributed to cm-1 acid-COOH, | 3.4 Regression coefficients analysis carboxylic with the band at 1655 attributed to amide I and aromatic C C (Bart”
Identifying the fingerprint of permanganate oxidizable carbon as a measure of labile soil organic carbon using Fourier transform mid‐infrared photoacoustic spectroscopy DOI: 10.1111/ejss.13085 -
Ring structure confidence 1.0
“ring),1547cm-1 stretching,1709cm-1,1706cm-1,1705cm-1 for (b), (c) due to C=C bond for (a),(b),(c) pyrrole 3161cm-1 (a),3399cm-1 3127cm-1for (b),3362cm-1 3128cm-1 respectively due to C=N stretching, for and and for (c) are assigned to the pr”
Synthesis, characterization, morphological and electrical studies of polypyrrole nanostructures DOI: 10.1063/1.5093829 -
Hydrogen bond confidence 1.0
“CdO cm-1 before surface modification there is a peak at 1706 which suggests that the terminal acid groups are participating in processes.4,20 intermolecular hydrogen bonding After esterification, we see two peaks in the carbonyl region, a p”
Mahapatro 等 - 2006 - Surface modification of functional self-assembled DOI: 10.1021/la052817h -
Silicon (Si) confidence 1.0
“Furthermore, to detect adulterated saffron from samples of unknown origin, a comparison of the ATR-FTIR spectra were carried out with spectra of pure saffron and results 2 cm-1 showed that the peaks at 1706, 1732, and 1225 (linked to crocin”
Naim 等 - 2022 - ATR-FTIR spectroscopy combined with DNA barcoding DOI: 10.1016/j.vibspec.2022.103446 -
Acetate confidence 1.0
“The peak at 1705.5 C_O peaks e and f) is compatible with the saturated stretching mode cm-1 (solid arrow) is compatible of ketones [37];”
Rapid detection and quantification of haptophyte alkenones by Fourier transform infrared spectroscopy (FTIR) DOI: 10.1016/j.algal.2016.07.006 -
Carbonyl (C=O) confidence 1.0
“the other 1706 cm-', hand, appears peak in are involved an interaction with the indicates that almost all carbonyl groups 05”
STRALIN 和 HJERTBERG - 1992 - A FTIR STUDY OF INTERFACIAL INTERACTIONS BETWEEN E DOI: 10.1163/156856192X00584
Have a spectrum with this band?
Upload your FTIR spectrum and get a full interpretation report — peak assignments with literature citations, library matches, and a literature-backed analysis — in seconds.