What absorbs at 2973 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 2973 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 2973 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

  “maybe due to the variation in the force exerted on the C-O-C enced the spectrum characteristic The three peaks at 2973,2937and2881cm-1are band behind the transfer of energy.”

  Studies of the behavior of reverse nonionic surfactant Pluronic 31R1 in aqueous and Propylammonium acetate (PAAc) ionic liquid solutions DOI: 10.1007/s10965-020-02315-x
• Alkyl C-H confidence 1.0

  “formate ions can be seen from the vibrations peak at ~1560 The broad peak seen cm-1 centered at ~2793 corresponds to C-H vibration [24], while the two obvious shoulder cm-1 cm-1 peaks at ~2973 and at ~3183 correspond to N-H bending and N-H”

  Proton-Conducting Biopolymer Electrolytes Based on Carboxymethyl Cellulose Doped with Ammonium Formate DOI: 10.3390/polym14153019
• Alkyl C-H confidence 1.0

  “The characteristic band of the isosorbide monomer -OH groups is cm-1, cm-1 is observed at 3366 whereas the band at 2973 corresponds to the isosorbide methylene observed at 3366 cm-1, whereas the band at 2973 cm-1 corresponds to the isosorbi”

  Gregori Valdes 等 - 2018 - Synthesis and Characterization of Isosorbide-Based DOI: 10.3390/polym10101170
• Alkyl C-H confidence 1.0

  “Ethanol also shows two C-H stretching 2 cm-1 bands at 2973.24 and 2928.46 due to CH and CH group (Table 4).”

  Hema 等 - 2022 - Structural and vibrational study of molecular inte DOI: 10.21203/rs.3.rs-649250/v1
• Alkyl C-H confidence 1.0

  “The absorption band situated at 2973 correspondsto aliphatic methylene”

  Synthesis Characterization and Highly Protective Efficiency of Tetraglycidyloxy Pentanal Epoxy Prepolymer as a Potential Corrosion Inhibitor for Mild Steel in 1 M HCl Medium DOI: 10.3390/polym14153100
• Aromatic ring confidence 1.0

  “IR spectrum, max, 3448 & 3277 ¼ C-H pyrazoline), 4.02 (1H, dd, J 12.4 Hz and 6.0 Hz, Hb protons of (amine stretching), 3048 (aromatic stretching), 2973, 2929 pyrazoline),4.40(2H,q,J¼7.2Hz,-CH (aliphaticC-Hstretching),1730(C]Ostretchingofd-l”

  Coumarin–carbazole based functionalized pyrazolines: synthesis, characterization, anticancer investigation and molecular docking DOI: 10.1039/d1ra03970a
• Alkyl C-H confidence 1.0

  “Heat maps plotting clusters of contents of phenol compounds, TPC and TFC analysed by The bands at 2973 cm-1, 2927 cm-1, and 2880 cm-1 are characteristics of C-H stretching”

  Characterisation of the Phenolic Profile of Acacia retinodes and Acacia mearnsii Flowers’ Extracts DOI: 10.3390/plants11111442
• Alkyl C-H confidence 1.0

  “Furthermore, peaks at: 1735 cm-1, 2914 cm-1, and 2973 cm-1 originate from CH vibrations in lipids [61].”

  FTIR and Raman Spectroscopy-Based Biochemical Profiling Reflects Genomic Diversity of Clinical Candida Isolates That May Be Useful for Diagnosis and Targeted Therapy of Candidiasis DOI: 10.3390/ijms20040988