What absorbs at 3623 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 3623 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 authoritative 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 3623 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

  “cm-1 cm-1 The sharp peaks at 3623.22 and 3702.31 were ascribed to the inner surface N-H stretching and inner hydroxyl group with higher amount of Al-OH in the octahedral sheet, respectively.”

  Preparation and characterization of adsorbents derived from bentonite and kaolin clays DOI: 10.1007/s13201-018-0827-2
• Hydroxyl (O-H) confidence 1.0

  “In the 1), FTIR spectrum of the halloysite clay mineral sample (spectrum the peaks at 3698 and cm-1 3623 were due to the stretching vibrations of the OH groups of the Al-OH.”

  Enhancing the Thermal Stability of Ionogels: Synthesis and Properties of Triple Ionic Liquid/Halloysite/MCC Ionogels DOI: 10.3390/molecules26206198
• Hydrogen bond confidence 1.0

  “Comparing the hydrogen bonding carboxylic acid O-H stretching appeared spectrum of the nanocomposite with the spectrum of the 3623cm-1.”

  Alkurdi 等 - 2022 - Development and Evaluation of a Novel Polymer Drug DOI: 10.1155/2022/7903310
• Hydroxyl (O-H) confidence 1.0

  “3697 O-H stretching 3623 O-H stretching 3440 O-H stretching, hydration”

  Caccamo 等 - 2020 - Self-Assembly Processes in Hydrated Montmorillonit DOI: 10.3390/ma13051100
• Hydroxyl (O-H) confidence 1.0

  “The stretching cm-1 region shows the typically broad band at 3623 assigned to the vibrations of the region shows the typically broad band at 3623 cm-1 assigned to the vibrations of the OH”

  The Antimicrobial Properties of Modified Pharmaceutical Bentonite with Zinc and Copper DOI: 10.3390/pharmaceutics13081190
• Hydroxyl (O-H) confidence 0.9

  “Explicit assignment: 'υOH at 3623 cm-1'”

  The Influence of Long-Time Storage on the Structure and Properties of Multi-Block Thermoplastic Polyurethanes Based on Poly(butylene adipate) Diol and Polycaprolactone Diol DOI: 10.3390/ma16020818