What absorbs at 1732 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 1732 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 1732 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

• Ester confidence 1.0

  “C¼O C-O-C -CH2), hemicelluloses (particularly functional groups related to cellulose I and/or II (OH, and Materials Chemistry cm(cid:2)1), C¼Car) and lignin (OH phenolic, Car-O and and provides qualitative inforacetoxy ester band at 1732 Na”

  Structural characterization of Argania spinosa Moroccan wooden artifacts during natural degradation progress using infrared spectroscopy (ATR-FTIR) and X-Ray diffraction (XRD) DOI: 10.1016/j.heliyon.2019.e02477
• Acetate confidence 1.0

  “Changes in the peaks of the FTIR spectrum at 2852 cm-1 (C-H stretching), 1732 (C=O stretching) and 1234 (C-O stretching) indicated that the alkali treatment completely removed hemicelluloses and lignin from the fiber surface.”

  Isolation and Characterization of Cellulose Nanocrystals from Oil Palm Mesocarp Fiber DOI: 10.3390/polym9080355
• Ester confidence 1.0

  “Figure 2a for the untreated OPFL fiber cm-1 vibrational peak in the chemically treated OPFL fiber was reveals a peak at 1732 that was associated with the the crucial differentiating factor that supported the elimiC=O stretching of either ur”

  Extraction and Characterization of Nanocellulose from Raw Oil Palm Leaves (Elaeis guineensis) DOI: 10.1007/s13369-019-04131-y
• Hydroxyl (O-H) confidence 1.0

  “treatment samples, and were normalized with respect to the Amide I peak between 1700-1600 cm-1 was ignored, since it was originated from O-H stretchSaturated ester C=O stretching at 1732 originates 2O.21 ings of residual H Twenty major abso”

  Igci 等 - 2017 - Application of Fourier transform infrared spectros DOI: 10.17219/acem/65784
• Acetate confidence 1.0

  “The spectrum shows a distinct peak at 1732 which cm-1 indicates a C=O functional group, whereas the peaks in the region of 2800 to 2900 represent C-C stretching.”

  Co-Culture of Halotolerant Bacteria to Produce Poly(3- hydroxybutyrate-co-3-hydroxyvalerate) Using Sewage Wastewater Substrate DOI: 10.3390/polym14224963
• Carbohydrate confidence 1.0

  “The spectrum proven FTIR cm-1 that the condition of bleaching treatment changes the absorption intensity at bands 1732, 1540, and 1460 which due to the loss of hemicellulose and lignin.”

  Khorairi 等 - 2020 - Cellulose Powder from Piper nigrum L. Agro-Industr DOI: 10.17576/jsm-2020-4908-17
• Acetate confidence 1.0

  “A peak at 1732 in the spectrum of U-EFB showed a C=O acetyl group of hemicellulose ester or a carbonyl ester of p-coumeric lignin unit [9, 17].”

  Kuthi 和 Badri - 2014 - Effect of Cooking Temperature on the Crystallinity DOI: 10.1063/1.4895240
• Carbonyl (C=O) confidence 1.0

  “The carboxylate peak at 1625 is weak and does not interfere 20 21 cm-1, with the MA peak at 1732 while the IA carbonyl peak significantly interferes with the 22”

  Loginova 等 - 2016 - Quantification of copolymer composition (methyl ac DOI: 10.1039/C5AY02264A.