What absorbs at 630 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 630 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 630 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) confidence 1.0

  “MaterialsChemistryandPhysics258(2021)123910 cm(cid:0) 1 and 3571 the dehydroxylation, but the hydroxyl bands at 630 Table 5 cm(cid:0) 1 Mass loss vs.”

  Thermo-physical insights into a series of strontium substituted hydroxyapatite DOI: 10.1016/j.matchemphys.2020.123910
• Water (H2O) confidence 1.0

  “cm(cid:1)1 v Since the making'' ability, for the three cations, is band at 630 overlaps with the band of water, 4 Therefore, there are much more water molecules that interact to study ionic interactions by means of IR spectroscopy only with”

  Chen 等 - 2004 - ATR-FTIR spectroscopic studies on aqueous LiClO4, DOI: 10.1039/B311768E
• Silicon (Si) confidence 1.0

  “spectra:[8,9] Four typical peaks appear in the FTIR cm-1-640 cm-1 1) the peak centered at 630 due to the Si-H wagging-rocking modes;”

  Hou 等 - 2011 - Evolution of infrared spectra and optical emission DOI: 10.1088/1674-1056/20/7/077802
• Metal oxygen confidence 1.0

  “cm-1-625 cm-1 band in the region of 630 for all Ti-SnO samples which could be assigned 2 to the stretching vibrations of Sn-O-Sn [38,39].”

  High Efficient and Cost Effective Titanium Doped Tin Dioxide Based Photocatalysts Synthesized via Co-precipitation Approach DOI: 10.3390/catal11070803
• Hydroxyl (O-H) confidence 1.0

  “LLM confirmed rule peak-group candidate”

  Mamede 等 - 2018 - Potential of Bioapatite Hydroxyls for Research on DOI: 10.1021/acs.analchem.8b02868
• Hydroxyl (O-H) confidence 1.0

  “LLM confirmed rule peak-group candidate”

  Natasha 等 - 2008 - Fourier transform infrared study on sol-gel derive DOI: 10.4028/www.scientific.net/AMR.47-50.1185
• confidence 1.0

  “The characteristic peaks of FTIR at about 630 and 749 were attributed to the Mn-O and Ni-O stretching vibrations respectively.”

  Microwave synthesis and electrochemical characterization of Mn/Ni mixed oxide for supercapacitor application DOI: 10.1063/1.4917828
• Acetate confidence 1.0

  “The carbonate bending modes and ) are practically unaffected by CEPTE C-O ,833 cm-1 C-O ,630 cm-1 (ν Zn2+: Al3+ 300 the ratio, but the stretching mode cm-1) exhibits direct correlation.”

  Dependence of bonding interactions in Layered Double Hydroxides on metal cation chemistry DOI: 10.1016/j.molstruc.2016.06.045