What absorbs at 3291 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 3291 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 3291 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

• confidence 1.0

  “caribbeana 3291 in assigned to N-H stretching (secondary amide), but broader and moved to a lower wavenumbers.”

  Juarez-de la Rosa 等 - 2012 - Effects of thermal treatments on the structure of DOI: 10.1007/s10853-011-5878-9
• Amide confidence 1.0

  “2 the bands centred at ~ 3291 cm-1 3.4 FTIR analysis and 3089 corresponds to amide A and amide B of”

  Spectral profile index changes as biomarker of toxicity in Catla catla (Hamilton, 1822) edible fish studied using FTIR and principle component analysis DOI: 10.1007/s42452-020-3001-z
• Hydroxyl (O-H) confidence 1.0

  “O-H Stretching 3290.96 3275.61 3275.57 3275.99”

  Abead 等 - 2023 - Study physical characteristics of Polyvinyl Alcoho DOI: 10.15764/pche.2014.02001.
• Secondary amine confidence 1.0

  “PTh exhibited secondary amine stretching and bending The functional groups that were genercm-1 cm-1, vibration at 3291 ated on the nanodiamond surface in the process of the and 1597 respectively.”

  Ashraf 等 - 2014 - Preparation and properties of multilayered polymer DOI: 10.1515/polyeng-2013-0297
• Alkyl C-H confidence 1.0

  “The broad band observed at 3291 is due to cm-1 at the absorption shoulder indicate the -CH stretch of starch.”

  Ashri 和 Lazim - 2014 - A Study on the Effect of the Concentration of N,N- DOI: 10.1063/1.4895204
• confidence 1.0

  “cm-1 The spectra in Figure 6 show a peak at 3291 and 1032 caused by the stretching The spectra in Figure 6 show a peak at 3291 and 1032 cm-1 caused by the stretching vibration of N-H and the strong stretching of the S=O group, respectively.”

  Bhatia 等 - 2023 - The Effect of Sage (Salvia sclarea) Essential Oil DOI: 10.3390/gels9030233
• Hydroxyl (O-H) confidence 1.0

  “In quercetin spectra, the wide bands at 3392 and 3291 cm-1 correspond to -OH stretching.”

  Fabrication and Evaluation of Water Hyacinth Cellulose-Composited Hydrogel Containing Quercetin for Topical Antibacterial Applications DOI: 10.3390/gels8120767
• Hydroxyl (O-H) confidence 1.0

  “The structure, which belong to O-H vibrations appeared at the wavenumbers and absorbance intensities at these bands 3290.69cm-1 wavenumber at 3332.39 and for the Whatman”

  Investigate the role of fungal communities associated with a historical manuscript from the 17th century in biodegradation DOI: 10.1038/s41529-022-00296-4