What absorbs at 3600 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 3600 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.

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 3600 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

  “RIPT cm-1 cm-1, 3600 is due to OH stretching.”

  Structural and magnetic properties of Co-doped ZnO thin films grown by ultrasonic spray pyrolysis method DOI: 10.1016/j.spmi.2016.11.069
• Hydroxyl (O-H) confidence 1.0

  “cm-1 In FTIR spectra, the range of 3600-3200 shows a broadband attributed to the stretching of O-H in water molecules.”

  Cu2+–Mn2+-Co-doped CdO nanocrystallites: comprehensive research on phase, morphology and optoelectronic properties DOI: 10.1007/s11164-020-04202-y
• Hydroxyl (O-H) confidence 1.0

  “OH stretching band at 3600 Th e Hoytville and Lamberton whole soil and clay are also”

  Calderon 等 - 2011 - Chemical Differences in Soil Organic Matter Fracti DOI: 10.2136/sssaj2009.0375
• Water (H2O) confidence 1.0

  “3600cm-1 absorbance of the deconvoluted water peaks.”

  Chan 和 Bogomolni - 2012 - Structural Water Cluster As a Possible Proton Acce DOI: 10.1021/jp304934t
• Carbohydrate confidence 1.0

  “(2007) attributed a decrease in peak-, hot pasteand break3600 The spectral changes in starches caused by c-irradiation down-viscosity to the decrease in size of the starch granules of potatoes were also apparent in the O-H R.”

  Ezekiel 等 - 2007 - Physicochemical, thermal and pasting properties of DOI: 10.1016/j.foodchem.2007.05.018
• Water (H2O) confidence 1.0

  “water molecules with OH stretching absorption at 3600 and HOH bending mode at 1610-1620 In addition cm(cid:1)1, cm(cid:1)1 to the S-OH totally symmetric mode at 950 adsorbed sulfate species gave two bands at 1230-1100 between HSO(cid:1) E m”

  Futamata 等 - 2005 - ATR-SEIR study of anions and water adsorbed on pla DOI: 10.1016/j.susc.2005.06.020
• Hydroxyl (O-H) confidence 1.0

  “O p e cm-1, 0-ν, ν ν=stretching Δν=ν n 0=monomeric OH stretching frequency at 3600 frequency where S Å=10-10 c observed in the infrared (IR) region and R=hydrogen bond distance in Å (1 m).”

  Gupta 等 - 2022 - In vitro cell composition identification of wood d DOI: 10.1098/rsos.201935
• Hydroxyl (O-H) confidence 1.0

  “9(cid:3)1019 [16] N-H N-H stretching 3400 3.2(cid:3)1020 [16] O-H H-O-H stretching 3500 3.2(cid:3)1020 [16] O-H SiO-H stretching 3600 Fig.”

  Effect of PECVD silicon oxynitride film composition on the surface passivation of silicon wafers DOI: 10.1016/j.solmat.2011.09.052