What absorbs at 3337 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 3337 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 3337 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

• Protein confidence 1.0

  “LLM confirmed rule peak-group candidate”

  Biogenic Synthesis Of Silver Nanoparticles Using Pod Extract Of Cola Nitida: Antibacterial, Antioxidant Activities And Application As Additive In Paint DOI: 10.1016/j.jtusci.2015.10.010
• Hydroxyl (O-H) confidence 1.0

  “The peak at 3337 and 3344 are assigned to the hydroxyl functional groups (O-H) cm-1 due to the moisture in the raw sample.”

  Study of biochar from pyrolysis and gasification of wood pellets in a nitrogen plasma reactor for design of biomass processes DOI: 10.1016/j.jece.2019.103391
• Hydroxyl (O-H) confidence 1.0

  “The lowering of the intensities of OH stretching band at 3337 cm-1 cm-1 and OH in-plane bending mode at 1337, 1312 and 1203 in the acetylated cotton spectra also provide further evidence of successful acetylation.”

  Adebajo 等 - 2006 - Raman spectroscopic investigation of acetylation o DOI: 10.1016/j.saa.2005.07.045
• Carbohydrate confidence 1.0

  “AFM also confirmed the interlocking between middle band at 3337 was ascribed to cellulose OH stretching MCC particles using contact mode analysis which showed that vibrations and intramolecular H-bonding [23,24].”

  Al-khattawi 等 - 2014 - Evidence-Based Nanoscopic and Molecular Framework DOI: 10.1371/journal.pone.0101369
• Hydroxyl (O-H) confidence 1.0

  “The wide absorbance band with a peak at 3337 cm-1 is attributed to the O-H The wide absorbance band with a peak at 3337 is attributed to the O-H stretching stretching vibration of alkynes, alcohols, and phenols [49,50], whereas the overlapp”

  Eucalyptus globulus and Salvia officinalis Extracts Mediated Green Synthesis of Silver Nanoparticles and Their Application as an Antioxidant and Antimicrobial Agent DOI: 10.3390/plants11081085
• Hydroxyl (O-H) confidence 1.0

  “wave number 0-4000 cm-1 IR spectrum for CHPTAC in Figure 4b shows a broad absorption band at 3337 which is w/v assigned to the O-H stretching vibration of water since the CHPTAC is 60% in liquid form.”

  Preparation and Optimization of Water-Soluble Cationic Sago Starch with a High Degree of Substitution Using Response Surface Methodology DOI: 10.3390/polym12112614
• Hydroxyl (O-H) confidence 1.0

  “cm-1 cm-1 The broad band at 3336.8 is due to O-H stretching.”

  Physical Properties of Carboxymethyl Cellulose from Palm Bunch and Bagasse Agricultural Wastes: Effect of Delignification with Hydrogen Peroxide DOI: 10.3390/polym12071505
• Hydroxyl (O-H) confidence 1.0

  “MP2/aug-cc-pVDZ calculations suggest the assignment cm-1, which only occur at of the two bands at 3337 and 3227 mmi higher methanol concentration, to the structure shown in S1.3 Bands due to free O-H or N-H stretching modes in Fig.”

  Zischang 等 - 2011 - Communication Where does the first water molecule DOI: 10.1063/1.3624841