What absorbs at 1664 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 1664 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 1664 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

• Alkyl C-H

  Reported band

  1664 cm-1

  Assignment

  Alkyl C-H

  Material / context

  Acrylonitrile based; polysaccharide; acetomannan polysaccharide

  Synthesis of Aloevera/Acrylonitrile based Nanoparticles for targeted drug delivery of 5-Aminosalicylic acid DOI: 10.1016/j.ijbiomac.2017.08.085
• Acetate

  Reported band

  1664 cm-1

  Assignment

  Acetate

  Material / context

  in-situ< thermosensitive polymer/clay nanocomposite

  Thermal and Structure Analysis Based on Exfoliation of Clay in Thermosensitive Polymer by <i>in-situ</i> Polymerization DOI: 10.22146/ijc.40872
• Amide

  Reported band

  1664 cm-1

  Assignment

  Amide

  Material / context

  DFO-grafted ultrasmall; Ultrasmall Nanoparticles Across the Skin; DFO-grafted nanoparticles

  High-Sensitivity Permeation Analysis of Ultrasmall Nanoparticles Across the Skin by Positron Emission Tomography DOI: 10.1021/acs.bioconjchem.1c00017
• Acetate

  Reported band

  1664 cm-1

  Assignment

  Acetate

  Material / context

  OH Ratios on Bio-Based Polyurethane; Acacia mangium Liquefied Wood; bio-based

  Effects of NCO/OH Ratios on Bio-Based Polyurethane Film Properties Made from Acacia mangium Liquefied Wood DOI: 10.3390/polym15051154
• Carbonyl (C=O)

  Reported band

  1664 cm-1

  Assignment

  Carbonyl (C=O)

  Material / context

  cholesterol anchored arabinogalactan

  Cholesterol anchored arabinogalactan for asialoglycoprotein receptor targeting: synthesis, characterization, and proof of concept of hepatospecific delivery DOI: 10.1016/j.carres.2015.03.003
• Amide

  Reported band

  1664 cm-1

  Assignment

  Amide

  Material / context

  reverse osmosis membranes

  Autopsy of Used Reverse Osmosis Membranes from the Largest Seawater Desalination Plant in Oman DOI: 10.3390/membranes12070671
• Amide

  Reported band

  1664 cm-1

  Assignment

  Amide

  Material / context

  HCl; GG

  Development, characterization and In-vitro evaluation of guar gum based new polymeric matrices for controlled delivery using metformin HCl as model drug DOI: 10.1371/journal.pone.0271623
• Acetate

  Reported band

  1664 cm-1

  Assignment

  Acetate

  Material / context

  Gelatin-ZnO nanofibers; ZnO; ZnO NPs

  Babayevska 等 - 2021 - Fabrication of Gelatin-ZnO Nanofibers for Antibact DOI: 10.3390/ma14010103