What absorbs at 722 cm⁻¹ in an FTIR spectrum?
A band near 722 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 722 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 |
|---|---|---|---|
| Alkyl C-H | 17 | 15 | 1.0 |
| Methoxy (OCH3) | 3 | 3 | 1.0 |
| Methacrylate | 3 | 3 | 1.0 |
| C-O single bond | 3 | 3 | 1.0 |
| Acetate | 3 | 3 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
| Ring structure | 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 |
| Silicon carbon | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| Imide | 1 | 1 | 1.0 |
| Borate | 1 | 1 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| Fluorine (C-F) | 1 | 1 | 0.9 |
Ranking reflects accumulated literature evidence, not a single fixed rule. Always confirm against your sample context.
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 722 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
-
Water (H2O) confidence 1.0
“The positive peak at cm-1 *722 indicates that the librations of water molecules are enhanced by about Mg2?, cm-1.”
Guo 等 - 2013 - Drawing Out the Structural Information About the F DOI: 10.1007/s10953-013-9970-4 -
Alkyl C-H confidence 1.0
“[9] associated the peaks at 722 and (cid:3)C (cid:3)C condition at 55 shifted to 65 in the short-term cm(cid:4)1 730 to the methylene rocking in the crystalline”
Transitions in unmodified and modified bitumen using FTIR spectroscopy DOI: 10.1617/s11527-018-1308-7 -
Alkyl C-H confidence 1.0
“The peak at 721.79 was attributed to cm-1 cm-1 the -(CH2)ndeformation [27,28].”
Study on the Effect of Fe3+ on Zircon Flotation Separation from Cassiterite Using Sodium Oleate as Collector DOI: 10.3390/min7070108 -
confidence 1.0
“(O-C-O) and valence and deformation at 722 cm-1 at 946 [29].”
Polu 等 - 2015 - Poly(ethylene oxide)-lithium difluoro(oxalato)bora DOI: 10.1007/s11581-015-1474-3 -
Acetate confidence 1.0
“1118.47 Strong C-O stretching Secondary alcohol - 722”
Characterization of Malaysian Jatropha Seed Oil and Discovering the Process of Powdered Jatropha Leaves DOI: 10.3390/pr10122577 -
Imide confidence 1.0
“FTIR (KBr, (C=O 3413 (OH stretching), 1778, 1717 (imide I), 1397 (imide II, CN stretching), 722 bending).”
Corrosion Resistance of Mild Steel Coated with Phthalimide-Functionalized Polybenzoxazines DOI: 10.3390/coatings10111114 -
Amide confidence 1.0
“Dynamic-thermal mechanical analysis cm-1 (CvO 1542 stretching vibration in the amide I and II cm-1 cm-1 (N-H The DTMA data for HMA7 was acquired using a Netzsch TMA bond), 1464 deformation vibration), and 1243 cm-1 (C-N vibration).28 402 F1”
Bhullar 等 - 2021 - Advanced spectroscopy, microscopy, diffraction and DOI: 10.1039/d0py01348j -
Alkyl C-H confidence 1.0
“The peak observed at 722 belongs to CH”
Optimization of Electrochemical Visualization of Latent Fingerprints with Poly(Neutral Red) on Brass Surfaces DOI: 10.3390/polym13193220
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