What absorbs at 1722 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 1722 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 1722 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

• Acetate confidence 1.0

  “The test cm-1 1722 peak is assigned the n(C=O) groups, at the”

  Bakan 等 - 2019 - Synthesis, characterization, toxicity and in vivo DOI: 10.1007/s10965-019-1901-7
• Imide confidence 1.0

  “All band at position 1722 these changes may be due to the partial destruction at the imide and aromatic sites and carbonization of the implanted layer of Kapton-H.”

  Chhokkar 等 - 2020 - Electrical and Structural Characterization of 100 DOI: 10.1063/5.0023335
• Carboxyl (COOH) confidence 1.0

  “Upon bubbling CO 2, a new which was considered as a critical parameter to be taken into 2 cm-1 peak centered at 1722 assigned to the symmetric stretching consideration as a result of proton shuttling phenomenon to form for the COO moiety of”

  Eftaiha 等 - 2017 - Bis-tris propane in DMSO as a wet scrubbing agent DOI: 10.1039/C7NJ02130E.
• Acetate confidence 1.0

  “A band due to free esters and acids C=O stretch are observed at 1722.43 and 1728.22”

  Firsoni 等 - 2019 - Fiber Content and Relative Feed Value Estimation o DOI: 10.1088/1757-899X/546/4/042008
• Ester confidence 1.0

  “A peak was also observed at 1722 for JF and AJF that may attribute to ester-based compounds that could have been used by supplier in the”

  In-situ Production and Collection of Bacterial Cellulose on Jute and Flax Mats by Static Cultivation DOI: 10.1080/15440478.2020.1870638
• Acetate confidence 1.0

  “Another solution and then adjusted to each predescribed pH with 1 N sodium to minor peak at 1722 cm-' due the C=O stretching band of hydroxide (NaOH) or M hydrogen chloride (HCl) aqueous solution to 6”

  Vibrational Spectroscopic Studies on the Disulfide Formation and Secondary Conformational Changes of Captopril–HSA Mixture after UV-B Irradiation DOI: 10.1562/2005-04-25-RN-497
• Carbonyl (C=O) confidence 1.0

  “cm-1 ∼1722 band relative to those due to carbonyl groups at suggests that SOZ may, in fact, be the major reaction product.”

  McIntire 等 - 2009 - Secondary Ozonide Formation from the Ozone Oxidati DOI: 10.1021/jp901535t
• Acetate confidence 1.0

  “However, for NIP, the C=O peak was at 1722 and the 226 cm-1.”

  Synthesis, characterization, and application of β-cyclodextrin-based ion-imprinted polymer for selective sequestration of Cr(VI) ions from aqueous media: Kinetics and isotherm studies DOI: 10.1016/j.molliq.2019.111991