What absorbs at 3628 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 3628 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 3628 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

• Alkene (C=C) confidence 1.0

  “transformation of epoxy group are observed at 1715 cm-1 bending of C-H double bond of vinyl groups, and 910 cm-1 A broad vibration between 3628 and 3142 is associated corresponds to double bonds of styrene monomer.”

  Eduardo Correa 等 - 2017 - Influence of tribological test on the global conve DOI: 10.1590/0104-1428.14916
• Hydroxyl (O-H) confidence 1.0

  “All the FTIR 136 spectra have a band at 3628 cm-1, which is attributed to the elongation vibration of the OH 137”

  Optimization of the Pentachlorophenol Adsorption by Organo-Clays Based on Response Surface Methodology DOI: 10.3390/ma15207169
• Water (H2O) confidence 1.0

  “The water O-H stretches at 18O 3631cm-1 assign water stretching vibrations, we normally use 3628 and probably correspond to the previously Fukuda et al.: Water vibration of Clpump in water 171 2685cm-1, bonding strength of such water molecu”

  Fukuda 等 - 2013 - Detection of a protein-bound water vibration of ha DOI: 10.2142/biophysics.9.167
• Hydroxyl (O-H) confidence 1.0

  “They were found as red-shift peaks due to the difference of surface binding or adsorption strength between the different Pd catalysts since the hydroxyl group vibration of the free hemiaminal is 3628 cm-1, according to DFT calculation at th”

  Underlying Mechanisms of Reductive Amination on Pd-Catalysts: The Unique Role of Hydroxyl Group in Generating Sterically Hindered Amine DOI: 10.3390/ijms23147621
• N h confidence 1.0

  “1 3600 Hydroxyl groups of the glucose and the -NH stretching cm-1 The peaks at 3628, 1544, and 1231 in the biomass were reduced and broadened.”

  Bonding Behavior and Mechanism of U(VI) by Chemically Modified Deinococcus radiodurans DOI: 10.3390/min11101108
• Water (H2O) confidence 1.0

  “istic absorption band at 3400 cm-1 due to the O-H stretching of adsorbed water and the 2 cm-1 characteristic absorption band at 3400 due to the O-H stretching of adsorbed water shoulder at 3628 cm-1 due to structural -OH groups of MMT.”

  Assessing the Carboxymethylcellulose Copper-Montmorillonite Nanocomposite for Controlling the Infection of Erwinia carotovora in Potato (Solanum tuberosum L.) DOI: 10.3390/nano11030802