What absorbs at 697 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 697 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 697 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

• Alkyl C-H confidence 1.0

  “1597cm-1 50 Aromatic C=Cstretch 45 40 cm-1 697 out of 35 plane C-H bend”

  Structure Assignment of Seized Products Containing Cathinone Derivatives Using High Resolution Analytical Techniques DOI: 10.3390/metabo11030144
• Acetate confidence 1.0

  “1880-1866 ≅697+1163 SiO2 combination band C=O stretching Intense Weak ≅697+1072 1783 SiO2 combination band”

  FTIR photoacoustic spectroscopy for identification and assessment of soil components_ Chernozems and their size fractions DOI: 10.1016/j.pacs.2020.100162
• Alkyl C-H confidence 1.0

  “Peaks at (741,697 cm-1) and (598 cm-1) corresponds to CH bending and C-OH bending respectively.”

  Kumar 等 - 2021 - Centella asiatica mediated facile green synthesis DOI: 10.1016/j.inoche.2021.108865
• confidence 1.0

  “The observed strong peaks at 697 are assigned to the Mg-O stretching vibration and the lon-”

  Microwave assisted CdO–ZnO–MgO nanocomposite and its photocatalytic and antibacterial studies DOI: 10.1007/s10854-018-9968-1
• Ring structure confidence 1.0

  “cm-1 Al(IV)-O-Si A new peak located at 697 corresponds to the bending vibration of tetra-coordinated in a cyclic structure emerged on the FT-IR spectra of the geopolymers.”

  Souissi 等 - 2022 - Synthesis, Thermal Properties and Electrical Condu DOI: 10.21203/rs.3.rs-1294285/v1
• Metal oxygen confidence 1.0

  “Furthermore, the band at 697 cm-1 indicated Fe-O-H stretching.”

  Veeramani 等 - 2022 - Vitamin Aand C-rich Pouteria camito fruit derive DOI: 10.4314/ahs.v22i1.78
• Acetate confidence 1.0

  “The bonds indicate what vibrations24-27) 697cm-1, C-O-C the stretching kinds of function groups exist on the GO.”

  Wang 等 - 2015 - Bilayer graphite-oxide anode for organic light-emi DOI: 10.7567/JJAP.54.042101
• Silicon (Si) confidence 1.0

  “suggested that the Si-OH bands located at 995 cm-1 cm-1, and 697 correabsorption peaks at 601”

  Yuan 等 - 2015 - Hydrophobic effect of silica functionalized with s DOI: 10.1007/s12039-015-0965-0