What absorbs at 1733 cm⁻¹ in an FTIR spectrum?
A band near 1733 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 1733 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) | 46 | 38 | 1.0 |
| Ester | 26 | 24 | 1.0 |
| Methacrylate | 26 | 23 | 1.0 |
| Acetate | 26 | 23 | 1.0 |
| Carboxyl (COOH) | 24 | 22 | 1.0 |
| Ketone | 23 | 21 | 1.0 |
| Amide | 23 | 21 | 1.0 |
| Carbohydrate | 5 | 5 | 1.0 |
| C-O single bond | 5 | 4 | 1.0 |
| Alkyl C-H | 4 | 4 | 1.0 |
| Methoxy (OCH3) | 4 | 3 | 1.0 |
| Acetyl | 3 | 3 | 1.0 |
| Imide | 3 | 1 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| Alkene (C=C) | 2 | 2 | 1.0 |
| Silicon (Si) | 2 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Phospholipid | 1 | 1 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| Lignin | 1 | 1 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 1.0 |
| N-O bond | 1 | 1 | 1.0 |
| Aldehyde (CHO) | 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 |
|---|---|---|---|
| PVA | 1733, 1660, 2930 | Acetate, Methacrylate, Carbonyl (C=O) | 1 |
| chitosan | 1733, 1650, 1655 | Acetate, Methacrylate | 1 |
| CuO | 1733, 453, 1000 | Methacrylate, Acetate | 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 1733 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
“1) vibration frequency (polysaccharide) 896 Anomeric carbon (C cm-1 In Fig.2, The peaks at 1733 were reduced with the decayed duration, arising from nonconjugated C=O in xylans due to the contribution of hemicellulose.”
Cheng 等 - 2011 - The Research on the Longitudinal Tensile Strength DOI: 10.4028/www.scientific.net/AMR.183-185.2014 -
Acetate confidence 1.0
“vibration at 2,861 A peak at 1733 corresponds to cm-1 C=O stretching vibration and 1,640 is corresponding to a C=C group in PVA backbone and can be explained on the basis of intra/inter molecular hydrogen bonding with cm-1 the neighboring O”
Gandhi 等 - 2010 - Ultrasound assisted one pot synthesis of nano-size DOI: 10.1007/s10853-009-4158-4 -
Carboxyl (COOH) confidence 1.0
“The bands at cm-1 1733 and 1618.89 are assigned to vC=O in COOH and C=C vibration respectively.”
Haq 等 - 2018 - Fabrication of pure and moxifloxacin functionalize DOI: 10.1016/j.jphotobiol.2018.07.011 -
Acetate confidence 1.0
“Foods2022,11,2786 10of13 1733cm-1 This indicates that the newly formed bands in the FTIR spectra at are the same O-C=O bonds as measured using XPS.”
Hauswirth 等 - 2022 - Spectroscopic Investigation of the Impact of Cold DOI: 10.3390/foods11182786 -
Acetate confidence 1.0
“FTIR spectroscopy peak absorbance in 1732.81 who is the peak absor- @ bance of carbonyl bond (C O) and two peaks absorbance cm(cid:2)1 m The chemical structure of bitumen is complex and bituof stretching vibration (1193.61 for and”
Li 等 - 2008 - The research of GMA-g-LDPE modified Qinhuangdao bi DOI: 10.1016/j.conbuildmat.2007.03.007 -
Alkyl C-H confidence 1.0
“The absorption peak of cane (a), absorption peaks of hydroxyl and amine cm-1), cm-1), cm-1 polysaccharide at 800 (3297 C-H (2926, 1456 and 1375 carbonyl greatly weakened, and the cm-1) cm-1), (1733 and 1653 absorption intensity of C-H (1374”
Lyu 等 - 2019 - XPS and FTIR studies of fungus-stained Daemonorops DOI: 10.1007/s11676-018-0598-5 -
Ester confidence 1.0
“cm-1 associated with the ester bond A band located at 1733 was evident in the cured films, the intensity of which increased temperature.8,19,34 with the Nevertheless, this band was less pronounced in the cured CH”
Rivero 等 - 2012 - Heat Treatment To Modify the Structural and Physic DOI: 10.1021/jf204077k -
Carbonyl (C=O) confidence 1.0
“Assigned to v(C=O) of MMA.”
Effect of lithium salt concentrations on blended 49% poly(methyl methacrylate) grafted natural rubber and poly(methyl methacrylate) based solid polymer electrolyte DOI: 10.1016/j.electacta.2011.06.015
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