What absorbs at 1734 cm⁻¹ in an FTIR spectrum?
A band near 1734 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 1734 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) | 42 | 36 | 1.0 |
| Carboxyl (COOH) | 27 | 26 | 1.0 |
| Ester | 26 | 25 | 1.0 |
| Methacrylate | 24 | 22 | 1.0 |
| Acetate | 24 | 22 | 1.0 |
| Amide | 22 | 21 | 1.0 |
| Ketone | 20 | 19 | 1.0 |
| Carbohydrate | 8 | 7 | 1.0 |
| C-O single bond | 6 | 5 | 1.0 |
| Acetyl | 5 | 5 | 1.0 |
| Alkyl C-H | 5 | 5 | 1.0 |
| Methoxy (OCH3) | 5 | 4 | 1.0 |
| Aromatic ring | 3 | 3 | 1.0 |
| C c single bond | 3 | 3 | 1.0 |
| Alkene (C=C) | 2 | 2 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| Lignin | 2 | 2 | 1.0 |
| N h | 2 | 2 | 1.0 |
| N-O bond | 1 | 1 | 1.0 |
| Aldehyde (CHO) | 1 | 1 | 1.0 |
| Siloxane (Si-O-Si) | 1 | 1 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n 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 |
|---|---|---|---|
| starch | 1734, 1650, 1540 | Methacrylate | 1 |
| pectin | 1734, 1746, 1150 | Methacrylate, Carboxyl (COOH), Carbonyl (C=O) | 1 |
| nanocellulose | 1734, 1540, 1646 | Methacrylate | 1 |
| lignin | 1734, 1035, 1510 | Methacrylate | 1 |
| wood | 1734, 1740, 1730 | 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 1734 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
“∼1734 stretching, the carbonyl peak can be observed at After & Boutevin, 2000;”
Gupta 等 - 2013 - Functionalization of pectin by periodate oxidation DOI: 10.1016/j.carbpol.2013.06.069 -
confidence 1.0
“2700-2771 2750-2700 Ethyl Group CH3 of C2H5 vibration C]O Carbonyl of acids stretching vibration 1734 1700 N-H 1600-1622 1650-1600 Quinolones bending vibration”
A direct DRS-FTIR probe for rapid detection and quantification of fluoroquinolone antibiotics in poultry egg-yolk DOI: 10.1016/j.foodchem.2018.07.129 -
C c single bond confidence 1.0
“C¼O 1692 Stretching of benzoyl C¼O 1734 bonded acid Non-H nC¼C C¼O Amorphous 123 INDO 1591 of aromatic ring Stretching of benzoyl (Exo) C¼O 1683 H-bonded 44 acid in a cyclic dimer (Tg),”
Thermoanalytical and Fourier transform infrared spectral curve-fitting techniques used to investigate the amorphous indomethacin formation and its physical stability in Indomethacin-Soluplus® solid dispersions DOI: 10.1016/j.ijpharm.2015.10.042 -
Carbohydrate confidence 1.0
“Holz Roh-Werktioed against carbohydrate peaks at 1734, 1375, cm(cid:1)1.”
Examination of the lignin content in a softwood and a hardwood decayed by a brown-rot fungus with the acetyl bromide method and Fourier transform infrared spectroscopy DOI: 10.1002/pola.20071 -
Carbohydrate confidence 1.0
“versicolor, lignin and carbobands at 1511, 1268 and xylan bands at 1734 hydrate reduction occurred at a similar rate, with a slight decrease in decayed wood.”
Pandey 和 Pitman - 2003 - FTIR studies of the changes in wood chemistry foll DOI: 10.1016/S0964-8305(03)00052-0 -
Alkene (C=C) confidence 1.0
“The reduced C=O and C=C peaks at 1734 cm-1 and 1536 cm-1, respectively, in the Fourier-transform Infrared (FTIR) spectra of isolated NC, confirmed the removal of appreciable amounts of hemicellulose and lignin components in the OPL fibers.”
Shunmugam 等 - 2021 - TAGUCHI ORTHOGONAL DESIGN FOR OPTIMIZING A UNIFIED DOI: 10.11113/jurnalteknologi.v83.15109 -
Aromatic ring confidence 1.0
“resistant rice starch where new peak was formed at 1734 Additionally, skeletal vibration involving carbon-carbon stretching within rings of aromatic hydrocarbons in the starch structure cm-1.”
Singh 和 Sharanagat - 2020 - Physico-functional and structural characterization DOI: 10.1016/j.ijbiomac.2020.07.185 -
Acetate confidence 1.0
“In the spectrum of the leaf part of the plant,1st peak (3372.57 cm-1) belongs to OH group in the group of (COOH), 2nd peak (2916.72-2848.93 cm-1, doublet) belongs to the group of NH 2, 3rd peak (1734.36 cm-1) belongs to C=O group in the gro”
Tasci 等 - 2016 - Determination of alliin and allicin in the plant o DOI: 10.17660/ActaHortic.2016.1143.19
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