What absorbs at 1743 cm⁻¹ in an FTIR spectrum?
A band near 1743 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 1743 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) | 55 | 48 | 1.0 |
| Ester | 40 | 39 | 1.0 |
| Methacrylate | 34 | 34 | 1.0 |
| Acetate | 34 | 34 | 1.0 |
| Carboxyl (COOH) | 33 | 33 | 1.0 |
| Amide | 31 | 31 | 1.0 |
| Ketone | 28 | 28 | 1.0 |
| Fatty acid | 9 | 9 | 1.0 |
| Alkyl C-H | 9 | 9 | 1.0 |
| C-O single bond | 7 | 7 | 1.0 |
| Methoxy (OCH3) | 7 | 7 | 1.0 |
| Lipid | 5 | 5 | 1.0 |
| C c single bond | 3 | 3 | 1.0 |
| Methyl | 2 | 2 | 1.0 |
| Aldehyde (CHO) | 1 | 1 | 1.0 |
| Protein | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| N-O bond | 1 | 1 | 1.0 |
| Triglyceride | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
| Phosphorus | 1 | 1 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| N h | 1 | 1 | 0.8 |
| Phospholipid | 1 | 1 | 0.7 |
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 |
|---|---|---|---|
| PMMA | 1743, 1722, 1383 | Methacrylate, Acetate, 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 1743 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
-
confidence 1.0
“The amplitude of the 1743 band corresponds to The Oxygen Reaction in Cytochrome Oxidase Biochemistry, Vol.”
Gorbikova 等 - 2007 - Time-resolved ATR-FTIR spectroscopy of the oxygen DOI: 10.1021/bi701614w -
Alkyl C-H confidence 1.0
“a small peak at 2921.63 in both the films showed good C-H stretch, while a sharp peak cm-1 at 1743.3 in PAV indicated triglyceride ester linkage cm-1,1362.46 cm-1 [11];”
Synthesis and characterization of eco-friendly bioplastic from low-cost plant resources DOI: 10.1007/s42452-019-1460-x -
Acetate confidence 1.0
“1 C=O stretching vibration 1743 University, 2011.”
Kumar 和 Sidhu - 2013 - Synthesis and Characterization of PMMA-ZrO2 Nanoco DOI: 10.1063/1.4810163 -
Acetate confidence 1.0
“For ginger EO, the strong and sharp absorption peak at 1743 the cm(cid:0) cm(cid:0) C-- 1 1 C-O and the absorption peak at 721 were assigned to O stretching vibration peak, stretching absorption peak at 1154 vibration peak and the deformati”
Microencapsulation of ginger-based essential oil (Zingiber cassumunar roxb) with chitosan and oil palm trunk waste fiber prepared by spray-drying method DOI: 10.1016/j.csite.2020.100606 -
Acetate confidence 1.0
“(\CH ferentfromthoseofPOoo.Informationonthephysicalcharacteristicsof asymmetrical stretch), 2922 and 2853 (symmetrical and asym3 \CH2), (\C_O \C_C thedifferentblends,suchasthesolidfatcontentandmeltingandcrysmetrical stretching of 1743 stret”
Ng 等 - 2014 - Compositional and thermal characteristics of palm DOI: 10.1016/j.foodres.2013.10.035 -
Carbonyl (C=O) confidence 1.0
“Compared with P, the spectra of the EP showed the appearance of cm-1, cm-1,1408 cm-1, 1598 which were represented C=O stretching vibration, strong bands at 1743 C=O asymmetric stretching vibration and O-H deformation vibration respectively.”
Ouyang 等 - 2012 - Adsorption of Cu (II) from aqueous single metal so DOI: 10.4028/www.scientific.net/AMR.535-537.1601 -
Acetate confidence 1.0
“The weak bands at 1747,1666 and medium band at 1658 due to C= O stretch in parent coir have only shifted C=O stretch to medium band at 1743 and C cm-1 1750 in BA-Coir/(Py-Acetone) and Coir-BA(Py-Acetone)-C-BPO respectively;”
Rout 等 - 2017 - A green approach to produce silver nano particles DOI: 10.1016/j.surfin.2017.03.004 -
Amide confidence 1.0
“cm-1), (1547-1548 peaks the tyrosine peak (1516 the Karolinska cm-1), CvO C-N lipid ester stretching peak (1743 and the cm-1) (1573-1574 adenine peak (Table 1).”
Shi 等 - 2018 - Biochemical alterations of Candida albicans during DOI: 10.1039/c8an01452c
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