What absorbs at 1624 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 1624 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 1624 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 band at 2850.31 cm-1 attributed to H-C-H stretching (alkyl, aliphatic), 1623.65 cm-1 corresponded to OH-fibers (water absorption), and 1414.47 cm-1 was vibrations of HCH and OCH bonds (methyl groups).”

  Preparation and Characterization of Sound-Absorbent Based on Polystyrene Reinforced Primary Sludge and Fly Ash from Pulp Mill DOI: 10.14716/ijtech.v14i3.5131
• Carboxyl (COOH) confidence 1.0

  “In the FTIR spectrum of sulfated xanthan, in comparison with the initial xanthan, cm-1, there is no absorption band at 1735 and there is a noticeable decrease in the band at cm-1, 1624 corresponding to the vibrations of the ionized carboxyl”

  Kazachenko 等 - 2021 - Food Xanthan Polysaccharide Sulfation Process with DOI: 10.3390/foods10112571
• Protein beta sheet confidence 1.0

  “For lysozyme, the most signifiThe peak at 1624 is usually assigned to changes of β-sheet cant peaks that led to the separation of the data points in lysoprotein structure and can indicate increased forcm-1, cm-1”

  Mcavan 等 - 2020 - Quantification of protein glycation using vibratio DOI: 10.1039/c9an02318f
• Hydroxyl (O-H) confidence 1.0

  “2327.77 Co 2 H-O-H bending vibration 1624.26 1624.31 1624.33 Zn-O stretching (metal oxide vibra510.01”

  Comparative study on dielectric and structural properties of undoped, Mn-doped, and Ni-doped ZnO nanoparticles by impedance spectroscopy analysis DOI: 10.1007/s10854-019-02517-0
• confidence 1.0

  “This could have caused the a amine band from 1618 cm-1 for pure urea to 1625 cm-1, 1624 cm-1, and 1624 cm-1 for urea-treated HNT.”

  Potency of Urea-Treated Halloysite Nanotubes for the Simultaneous Boosting of Mechanical Properties and Crystallization of Epoxidized Natural Rubber Composites DOI: 10.3390/polym13183068
• Alkyl C-H confidence 1.0

  “FT-IR 3066, 2984 (C-H, s, stretching), 1624 (C=N, m, bending), 1593, 1474 (CH=CH, w, bending), 1168 (C-N, m, bending), 1273 (C-O, 1H-NMR”

  A Comprehensive Approach to Derivatization: Elemental Composition, Biochemical, and In Silico Studies of Metformin Derivatives Containing Copper and Zinc Complexes DOI: 10.3390/molecules28031406
• Alkyl C-H confidence 1.0

  “CHD displayed peaks at 3325 and 3119cm(cid:3)1 The cumulative CHD release from both groups of tablets was (asymmetric and symmetric NH stretching vibrations), cm(cid:3)1 affectedbytheratioofP407.IncreasingP407contentelevatesdrug 2938 and 28”

  Al-Ani 等 - 2019 - The effect of the source and the concentration of DOI: 10.1016/j.jsps.2019.04.012
• C c single bond confidence 1.0

  “Strong, broad Methylene C-H asymmetric 2927 Strong, broad Methylene C-H asymmetric Aliphatic alkene Aliphatic alkene GSE 1624 Strong Skeletal C-C vibrations (methyne) Skeletal C-C vibrations GSE 1624 Strong”

  The Antimicrobial Activities of Silver Nanoparticles from Aqueous Extract of Grape Seeds against Pathogenic Bacteria and Fungi DOI: 10.3390/molecules26196081