What absorbs at 700 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 700 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 700 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

• Hydroxyl (O-H)

  Reported band

  700 cm-1

  Assignment

  Hydroxyl (O-H)

  Material / context

  Silane; silane-functionalized sodium montmorillonite nanoclay

  Silane functionalization of sodium montmorillonite nanoclay: The effect of dispersing media on intercalation and chemical grafting DOI: 10.1016/j.clay.2017.12.020
• Acetate

  Reported band

  700 cm-1

  Assignment

  Acetate

  Material / context

  silver nanoparticles of Microbacterium proteolyticum LA2; silver nanoparticles of Streptomyces rochei LA2; silver nanoparticles of Streptomyces rochei LA2(O)

  Antibacterial efficacy of synthesized silver nanoparticles of Microbacterium proteolyticum LA2(R) and Streptomyces rochei LA2(O) against biofilm forming meningitis causing microbes DOI: 10.1038/s41598-023-30215-9
• Hydroxyl (O-H)

  Reported band

  700 cm-1

  Assignment

  Hydroxyl (O-H)

  Material / context

  Cellulose

  IR Study on Cellulose with the Varied Moisture Contents: Insight into the Supramolecular Structure DOI: 10.3390/ma13204573
• Alkyl C-H

  Reported band

  700 cm-1

  Assignment

  Alkyl C-H

  Material / context

  its effect on silica reinforced tire; 3-octanoylthio-1-propyltriethoxysilane in styrene butadiene rubber: Characterization; 3-octanoylthio-1-propyltriethoxysilane grafted SBR

  Reactive grafting of 3-octanoylthio-1-propyltriethoxysilane in styrene butadiene rubber: Characterization and its effect on silica reinforced tire composites DOI: 10.1016/j.polymer.2019.121693
• Ring structure

  Reported band

  700 cm-1

  Assignment

  Ring structure

  Material / context

  colophony; diterpenoid resin; pitch

  Fourier transform infrared spectroscopy as a suitable technique in the study of the materials used in waterproofing of archaeological amphorae DOI: 10.1016/j.aca.2007.07.021
• Silicon nitrogen

  Reported band

  700 cm-1

  Assignment

  Silicon nitrogen

  Material / context

  silicon oxynitride

  Effect of PECVD silicon oxynitride film composition on the surface passivation of silicon wafers DOI: 10.1016/j.solmat.2011.09.052
• Borate

  Reported band

  700 cm-1

  Assignment

  Borate

  Material / context

  europium doped zinc sodium bismuth borate glasses

  Red light emission from europium doped zinc sodium bismuth borate glasses DOI: 10.1016/j.physb.2017.09.113