What absorbs at 3405 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 3405 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 3405 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

  “cm-1 In contrast, the broad peaks at 3405 for SiO was attributed to -OH stretching vibrations whereas 2”

  Nanocellulose-silica polyethersulfone hybrid composite stabilized lipase for esterification DOI: 10.1063/1.5125521
• Hydroxyl (O-H) confidence 1.0

  “A strong and broad vibration band at 3405 ascribed due to the overlapping of O-H and amine N-H stretching bands [46].”

  Jaiswal 和 Dhayal - 2020 - Preparation of 2D coatings of functionally graded DOI: 10.1016/j.matchemphys.2020.122663
• Hydroxyl (O-H) confidence 1.0

  “cm-1 plot between hυ (eV) versus mode and the peak at 3405 is due to O-H stretching”

  Manikandan 等 - 2018 - Properties of sol gel synthesized ZnO nanoparticle DOI: 10.1007/s10854-018-8981-8
• Hydroxyl (O-H) confidence 1.0

  “cm-1 In the cellulose spectrum (Figure 5B), the broad band centered at 3405 is related to the cm-1 hydroxyl stretching vibrations.”

  Cellulose‐reinforced starch biocomposite: optimization of the effects of filler and various plasticizers using Design‐Expert method DOI: 10.1002/star.202000028.
• Hydroxyl (O-H) confidence 1.0

  “LLM confirmed rule peak-group candidate”

  Pyrolysis characteristics of ethanol swelling Shendong coal and the composition distribution of its coal tar DOI: 10.1016/j.jaap.2018.12.012
• Hydroxyl (O-H) confidence 1.0

  “In comparison, the peak at 3405.15 cm-1 represents OH.”

  Foliar Application of Nanoclay Promotes Potato (Solanum tuberosum L.) Growth and Induces Systemic Resistance against Potato Virus Y DOI: 10.3390/v14102151
• Hydroxyl (O-H) confidence 1.0

  “cm-1 cm-1 Furthermore, the band at 1648 represented C=O stretching, while bands at 2876 cm-1 and 3405 represented O-H stretching groups, which signify the formation of CaOH 2 at 1648 cm-1 represented C=O stretching, while bands at 2876 cm-1”

  Assiry 等 - 2023 - Microstructural and Elemental Characterization of DOI: 10.3390/app13074517
• Hydrogen bond confidence 1.0

  “It was reported that the ~3280 cm-1 peak is related to the intermoleccm-1 cm-1 intermolecular hydrogen bonds, while ~3328 and ~3405 can be assigned to the ular hydrogen bonds, while ~3328 cm-1 and ~3405 cm-1 can be assigned to the intramole”

  Impact of NaOH Concentration on Deweaving of Cotton Fabric in Aqueous Solutions DOI: 10.3390/su13042015