Carboxyl (COOH) — FTIR absorption peaks and assignments

Quick answer

Carboxyl (COOH) is usually assigned by looking for a recurring cluster of characteristic peaks rather than one exact textbook number. The table below shows where the literature most often places this group in FTIR, ranked by accumulated evidence.

Characteristic FTIR peaks for Carboxyl (COOH)

Showing the 30 best-supported peaks of 1244 total for Carboxyl (COOH).

Possible materials

Spectrum logic

A functional-group assignment becomes more confident when several expected bands appear together. Use this page to find the strongest-supported peaks, then confirm that the same sample exhibits a coherent pattern rather than a single isolated hit.

Real-world usage

These pages are useful for unknown material analysis, peak explanation in reports, polymer troubleshooting, and verifying whether a candidate material family is chemically plausible.

Common mistakes

• Using one functional-group page as a complete material verdict without checking the rest of the spectrum.
• Assuming the strongest band is always the most diagnostic one.
• Forgetting that processing, additives, aging, and mixtures can shift or broaden expected peaks.

Verification advice

Use DSC, GC-MS, or TGA when several material families share similar bands or when mixture effects make the FTIR assignment uncertain.

Literature behind these assignments

• 1735 cm⁻¹ confidence 1.0

  “The new peak appears cm-1 at 1735 which indicates the presence of a C=O bond from carboxylic acid.”

  Synthesis and Physical Properties Characterization of Montmorillonite-modified Carbon Nanotubes Filler DOI: 10.1088/1757-899X/546/4/042004
• 945 cm⁻¹ confidence 1.0

  “CdO cm-1, the band in the ester group at 1751 that of 1700 cm-1 CdO cm-1 On the other hand, the Acesulfame-K band at 945 does due to the stretch in carboxylic acids, and the band CdO cm-1 not overlap with any Aspartame band, but the low sig”

  Armenta 等 - 2004 - FTIR determination of aspartame and acesulfame-k i DOI: 10.1021/jf049218l
• 1713 cm⁻¹ confidence 1.0

  “This means that the addition shows sharp absorption and low intensity at 1712.8 cm-1 of DVB is able to shift the hydroxyl bonds in blends, which indicates the presence of C=O carbonyl so that DVB makes the blends more compatible.”

  Grafting of Oleic Acid On Cyclic Natural Rubber Resiprene-35 Using Dicumyl Peroxide Initiator and Divinylbenzene Compatibilizers For Paint Binder In Polyamide Thermoplastics DOI: 10.13005/ojc/350119
• 1723 cm⁻¹ confidence 1.0

  “The characteristics sharp peak at 1723 is attributed to stretching vibration of carbonyl (-C=O) group from GMSG/VMSG [46, 47], the intensity of which increases with the increase of GMSG/VMSG contents in the membrane”

  Novel Silica Functionalized Monosodium Glutamate/PVA Cross-linked Membranes for Alkali Recovery by Diffusion Dialysis DOI: 10.21203/rs.3.rs-283846/v1
• 1554 cm⁻¹ confidence 1.0

  “While in cobalt stearate, the absorption peak at wave number of 1554 cm-1indicate the presence of asymmetric vibrations of carboxylate groups absorption peak at the wave numbers of 3000”

  Synthesis of cobalt stearate as oxidant additive for oxo-biodegradable polyethylene DOI: 10.1063/1.4930711
• 1302 cm⁻¹ confidence 1.0

  “cm-1 cm-1, characteristic peaks at 1302 and 1416 which correspond to vibrational modes 3-) (COO-) of nitrate (NO and acetate ions [50,51].”

  Sol-Gel Synthesized High Entropy Metal Oxides as High-Performance Catalysts for Electrochemical Water Oxidation DOI: 10.3390/molecules27185951
• 1445 cm⁻¹ confidence 1.0

  “N-C=O stretching at 1445 Other absorption On the other hand, it can be seen from Fig.”

  Determination of iprodione in agrochemicals by infrared and Raman spectrometry DOI: 10.1007/s00216-007-1152-z
• 1629 cm⁻¹ confidence 1.0

  “The peak at 2922 3 cm-1 CEPTE 1629 is due to asymmetric stretching vibration of C=O carbonyl groups [28,29].”

  Investigation on impedance response and dielectric relaxation of Ni-Zn ferrites prepared by self-combustion technique DOI: 10.1016/j.jallcom.2017.02.241