What absorbs at 557 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 557 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

Ranking reflects accumulated literature evidence, not a single fixed rule. Always confirm against your sample context.

Possible materials

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 557 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

• Metal oxygen confidence 1.0

  “LLM confirmed rule peak-group candidate”

  Mesoporous magnetite nanoparticles synthesis using the Peltophorum pterocarpum pod extract, their antibacterial efficacy against pathogens and ability to remove a pollutant dye DOI: 10.1016/j.molstruc.2018.10.042
• Carbohydrate confidence 1.0

  “663 662 Out of plane bending vibration of intermolecular H-bonded O H group 666 558 557 Torsional vibration of pyranose ring 557 cm-1 cm-1”

  Kasyapi 等 - 2013 - Bionanowhiskers from jute Preparation and charact DOI: 10.1016/j.carbpol.2012.10.021
• Hydroxyl (O-H) confidence 1.0

  “Salama et al./Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 136 (2015) 1816-1826 805 905 473 goethite OH bending bands 557 Type 3”

  Spectroscopic characterization of iron ores formed in different geological environments using FTIR, XPS, Mössbauer spectroscopy and thermoanalyses DOI: 10.1016/j.saa.2014.10.090
• confidence 1.0

  “reveals the characteristic vibrational bands at 557, 688, 717, 881, 935 and 1039 The cm-1 vibrational modes at 557 and 717 are assigned to the structural vibrations of yttrium-oxygen cm-1 (Y-O) bonds, the peak at 688 to the stretching mode”

  Luminescence and electron spin resonance studies of narrow-band UVB emitting Gd3+ doped Y2SiO5 nanophosphors synthesized by sol-gel method DOI: 10.1016/j.ijleo.2021.167228
• Metal oxygen confidence 1.0

  “The metal-oxygen band at 557 corresponded to intrinsic cm-1 stretching vibrations of metal at the tetrahedral site, while the metal-oxygen band found at 425 was assigned to octahedral-metal stretching of Fe-O [53-55].”

  Yadav 等 - 2020 - Synthesis and Characterization of Amorphous Iron O DOI: 10.3390/nano10081551
• Silanol (Si-OH) confidence 1.0

  “attributed to the Si-O stretching vibration [18, 19], a peak causeMgislesselectronegativethanH,andconsequently, at799cm-1 resultsfromthe symmetricSi-Ostretchingvithe substitution of H (2.1) in Si-OH by Mg (1.2) would decm-1 bration, and pea”

  Zhang 等 - 2019 - Influence of Magnesia on Demoulding Strength of Co DOI: 10.1515/rams-2019-0008
• confidence 1.0

  “990cm-1 powder of white MTA Angelus root repair shows the presPlus, bands at have been assigned to asymmetric 43ence oftricalcium silicate (aliteofhatrurite,Ca stretching vibration of phosphate (PO ) [4], but those at 3(SiO 4)O;card 557cm-1”

  Abu Zeid 等 - 2017 - Chemistry and Bioactivity of NeoMTA Plus (TM) vers DOI: 10.1155/2017/8736428
• Amide confidence 1.0

  “Moreover, in the spectra of the control unheated films, the intensity cm-1 557 of the band of amide I at 1630 was always lower than that of the band of the amide II at cm-1, 558 1550 regardless of the Mw of chitosan/CDP, as a consequence of”

  Effect of glucose-induced Maillard reaction on physical, structural and antioxidant properties of chitosan derivatives-based films DOI: 10.1016/j.carbpol.2020.117341