What absorbs at 1770 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 1770 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 1770 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

• Carboxyl (COOH) confidence 1.0

  “dependent on the nature of the counterion, and has for example f 4+ been seen to increase in frequency in the sequence NH f Na+ Li+ in Raman experiments of perfluorodecanoic acid salts.37 and the corresponding Furthermore, the absence of th”

  Tyrode 等 - 2007 - A study of the adsorption of ammonium perfluoronon DOI: 10.1021/jp063912h
• Aromatic ring confidence 1.0

  “H+ estingly, by increasing the irradiation energy, the transmittancepeaksforC]Ostretchingvibrationaround1770cm(cid:3)1 and aromatic ring decrease while the transmittance peaks for cm(cid:3)1 C]O stretching vibration around 1700 and aromatic”

  A mechanism of surface hardness enhancement for H+ irradiated polycarbonate DOI: 10.1039/d0ra05073c
• Acetate confidence 1.0

  “In the EC spectrum, the strong doublet (1580-1700 carbonyl (1700-1840 and cm-1 cm-1) peaks at 1770 and 1796 are assigned to the C=O amine/hydroxyl groups (3130-3700 as shown in Fig.”

  Yusuf 等 - 2016 - From crab shell to solar cell a gel polymer elect DOI: 10.1039/C6RA04188D.
• Acetate confidence 1.0

  “The max cm-1 cm-1 peak at 1770 and 1395 in FTIR spectra of hydrolyzed dye showed that C-O groups appeared under relatively mild alkaline conditions.”

  Zhao - 2019 - Study on the hydrolysis performance of phthalimide DOI: 10.1016/j.dyepig.2018.12.043
• Anhydride confidence 1.0

  “The grafting reaction gave rise to three new absorption bands, at 1713 and 1743 cm-1, associated with the carbonyl stretching of the carboxylic acids of the itaconic acid [25-27] and at 1770 cm-1 associated with a five-membered anhydride ri”

  Aguilar-Bolados 等 - 2020 - SEBS-Grafted Itaconic Acid as Compatibilizer for E DOI: 10.3390/polym12030643
• Carboxyl (COOH) confidence 1.0

  “The assignments data of (pip)-magnesium, calcium, zinc, and iron (III) drug complexes show no absorption band cm-1, ν(C=O) at ~1770 which is characteristic of the stretching vibration of the carboxylic group, which is suggestive of the cont”

  Synthesis and Spectroscopic Characterizations of Some Essential Metal Ion (MgII, CaII, ZnII, and FeIII) Pipemidic Acid Chemotherapeutic Agent Complexes DOI: 10.3390/xxxxx
• Acetate confidence 1.0

  “In the FTIR spectrum of pure aspirin (Figure 7 A), = -1 several strong vibrations were presented at 1770 cm (C O Figure 8 X-ray diffraction pattern of (A) pure aspirin, (B) blank = -1 -1 stretch), 1600 cm (C C stretch), 1573 cm (OCO antisym”

  Banerjee 等 - 2013 - Influence on variation in process parameters for t DOI: 10.1515/secm-2012-0078
• Acetate confidence 1.0

  “Secondly, the C=O absorption peaks at 1806 and 1770 of PMDA are in close cm-1) cm-1 Secondly, the C=O absorption peaks at 1806 and 1770 cm-1 of PMDA are in close proximity to that in PI (1777 and are overlapped (or merged) into the 1777 pea”

  Interpenetration Networked Polyimide–Epoxy Copolymer under Kinetic and Thermodynamic Control for Anticorrosion Coating DOI: 10.3390/polym15010243