What absorbs at 3321 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 3321 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 3321 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

  “The peak at 3321 cm-I may be caused by the stretch of the University] and -OH groups.”

  Ha 等 - 2001 - Spectroscopic stuides on the liquid crystal alignm DOI: 10.1080/10587250108028259
• Hydroxyl (O-H) confidence 1.0

  “LLM confirmed rule peak-group candidate”

  Hanif 和 Zaman - 2017 - Thiolation of arabinoxylan and its application in DOI: 10.1186/s40199-017-0172-2
• confidence 1.0

  “N-H stretching arately, in screw-capped glass vials wrapped with band of-NH2 group appeared at 3321.18 cm-1.”

  Batool 等 - 2019 - USE OF GLUTARIC ACID TO IMPROVE THE SOLUBILITY AND DOI: 10.32383/appdr/94246
• Hydroxyl (O-H) confidence 1.0

  “6e), two bands at 3430, 3321 cm-1 were observed, typical of hydroxyl served absorption bands are typical for copper niand 3306”

  Curkovic 等 - 2021 - Electrochemical Characterization of Bronze Exposed DOI: 10.15255/CABEQ.2021.1926
• Hydroxyl (O-H) confidence 1.0

  “cm-1), O-H stretching vibration (3321.42 cm-1), frequency-inde- [31].”

  Preparation of Novel Nanoformulation to Enhance Efficacy in the Treatment of Cardiovascular Disease DOI: 10.3390/biomimetics7040189
• N h confidence 1.0

  “cm-1 and a broad signal The spectrum of the pure NIA contains the NH stretching vibration at 3321”

  Kacso 等 - 2012 - Structural characterization of ambazone salt with DOI: 10.3233/SPE-2012-0570
• Hydroxyl (O-H) confidence 1.0

  “cm-1 The number of waves associated with OH functional groups at 3321 cm-1 was reThe number of waves associated with OH functional groups at 3321 was reduced duced due to the formation of new hydrogen bonds between the bio-composite matrix”

  Part B: Improvement of the Optical Properties of Cellulose Nanocrystals Reinforced Thermoplastic Starch Bio-Composite Films by Ex Situ Incorporation of Green Silver Nanoparticles from Chaetomorpha linum DOI: 10.3390/polym15092148
• confidence 1.0

  “Secondary structure of collagen usually has an N-H cm-1 stretching peak at 3321 because of the standard fre-”

  Extraction and characterization of collagen from the skin of Pterygoplichthys pardalis and its potential application in food industries DOI: 10.1007/s10068-019-00601-z