What absorbs at 1764 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 1764 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 1764 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

• Hydrogen bond confidence 1.0

  “CdO cm-1 before surface modification there is a peak at 1706 which suggests that the terminal acid groups are participating in processes.4,20 intermolecular hydrogen bonding After esterification, we see two peaks in the carbonyl region, a p”

  Mahapatro 等 - 2006 - Surface modification of functional self-assembled DOI: 10.1021/la052817h
• Ester confidence 1.0

  “The FTIR analyses of the acetylated lignins then allowed for the phenolic OAc and aliphatic OAc groups to be distinguished by their respective ester C=O stretching vibrations at 1764 and 1744 cm-1.”

  The Effect of Sample Preparation Techniques on Lignin Fourier Transform Infrared Spectroscopy DOI: 10.3390/polym15132901
• Carbonyl (C=O) confidence 1.0

  “pennata) ostrich anda localmineral[6].Theobservationofa Despite the poor data quality of the archaeological sample cm(cid:3)1 sharp carbonyl band at 1764 spectrum due to the high background there is a clear in the FTIR of the reference coin”

  Maier 等 - 2007 - Combined use of vibrational spectroscopy and GC-MS DOI: 10.1016/j.vibspec.2006.09.003
• Ester confidence 1.0

  “cm-1 internal ester peak at ~1764 serves as a measure of reaction progress.”

  Semi‐Heterogeneous Dual Nickel/Photo‐catalysis using Carbon Nitrides: Esterification of Carboxylic Acids with Aryl Halides DOI: 10.1002/anie.201902785.
• Ketone confidence 1.0

  “The band at 1764 cm-1 belongs to the absorption of CO stretching for unconjugated ketones and γ lactones produced by the oxidation after the degradation of the aromatic ring.”

  Effect of Water Leaching on Photodegraded Scots Pine and Spruce Timbers Monitored by FTIR Spectroscopy DOI: 10.3390/f12070833
• Hydroxyl (O-H) confidence 1.0

  “Etoposide exhibits the characteristic intensities of a C=O cm-1 stretching absorption band at 1764 and the O-H stretch at”

  Thiyagarajan 等 - 2019 - Preparation and Biopharmaceutical Evaluation of No DOI: 10.4274/tjps.galenos.2018.21043
• Carbonyl (C=O) confidence 0.9

  “νC=O absorption band region”

  Antibacterial Activity of New Dibenzoxepinone Oximes with Fluorine and Trifluoromethyl Group Substituents DOI: 10.3390/ijms12106432