What absorbs at 1719 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 1719 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 1719 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

• Alkene (C=C) confidence 1.0

  “The peak at 1718.82 shows C=C stretching that indicated the”

  Fatima 等 - 2021 - Extraction and Chemical Characterization of Humic DOI: 10.3390/su13168969
• Acetate confidence 1.0

  “CH 2stretching The peaks of MDP-condiThe L929 mouse fibroblast cells (Cell Bank of the tioned nanoand micro-zirconia fillers located at cm-1 Chinese Academy of Sciences, Shanghai, China) were 1719 due to C=O stretching vibration and absorpt”

  Hong 等 - 2020 - Mechanical Properties of Nanohybrid Resin Composit DOI: 10.2147/IJN.S283742
• confidence 1.0

  “A new peak at 1719 was observed in the FTIR spectra that can  Mass Analysis be attributed to the loss of type one amine functionality.”

  Siahi 等 - 2018 - Analytical Investigation of the Possible Chemical DOI: 10.15171/apb.2018.074
• Acetate confidence 1.0

  “Figure 1 shows the XRD pattern of GO 1719cm-1 by the disappearance of the C=O bands (at ) and where a characteristic peak (002 plane) appears at 2 theta = 10.9∘ 2925cm-1 sp3 indicatingthepresenceofoxygencontainingfunctional the appearance o”

  Abdelhalim 等 - 2016 - Graphene Functionalization by 1,6-Diaminohexane an DOI: 10.1155/2016/1485280
• Carboxyl (COOH) confidence 1.0

  “3 4 5 C = O stretching vibration (carboxylic acid) 1719 1711”

  Polyesters Based on Linoleic Acid for Biolubricant Basestocks: Low-Temperature, Tribological and Rheological Properties DOI: 10.1371/journal.pone.0151603
• Carbonyl (C=O) confidence 1.0

  “C/(A+B) A/B cm-1, 1719 is related to the stretching vibration of the free PU 1.18 0.15 carbonyl from the urethane group whereas the second one cm-1,”

  Effect of PEG grafting density on surface properties of polyurethane substrata and the viability of osteoblast and fibroblast cells DOI: 10.1007/s10856-022-06668-1
• Acetate confidence 1.0

  “The cm-1 cm-1 bands at 1719 and 1687 can be attributed to the stretching of the C=O bond in carboxylic acids.”

  HPTLC and ATR/FTIR Characterization of Antioxidants in Different Rosemary Extracts DOI: 10.3390/molecules26196064
• Hydroxyl (O-H) confidence 1.0

  “Liu [90] related the intensity peaks at 1625 cm-1 and 1719 cm-1 to the O-H bending vibration cm-1”

  Effect of rGO wt.% on the Preparation of rGO/CuO Nanocomposites at Different Test Periods and Temperatures DOI: 10.3390/cryst12101325