What absorbs at 2980 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 2980 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 2980 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

• Alkyl C-H confidence 1.0

  “cm-1 The peak at 2980 (Figure 2(a)) which can be assigned to C-H (bond with NH 2) is interesting since it is only present in the modified NCC [23], hence it's intensity will have a direct correlation on the extent of reaction.”

  Indarti 等 - 2020 - Effect of temperature on the silylation of nanocry DOI: 10.1088/1755-1315/425/1/012065
• Alkyl C-H confidence 1.0

  “The bands at 510 and 506cm in DMn(CO) and HMn(CO) is 5 5 2980cm-1 The antisymmetric methyl stretching vibration at 5X spectra.”

  Mahmood 等 - 2006 - Comparative vapour phase FTIR spectra and vibratio DOI: 10.1016/j.saa.2005.11.024
• confidence 1.0

  “On the other hand, as shown in Figure 2B, after treatment of κ-carrageenan/starch membranes with an amylase enzyme, distinct peaks were visible at 3190-3380 cm-1 (s), due to N-H stretching of secondary amides, and 2980 cm-1, due to C-”

  Preparation and Characterization of Super-Absorbing Gel Formulated from -Carrageenan–Potato Peel Starch Blended Polymers DOI: 10.3390/polym13244308
• Alkyl C-H confidence 1.0

  “Emergence of this region with a peak at around 2980 are 242 attributed to the alkyl group exposure of peptide chains due to protein hydrolysis (Hsu, Weng, 243 Liao, & Chen, 2005).”

  Himalayan cheese (Kalari) fermented with different probiotic strains: In vitro investigation of nutraceutical properties DOI: 10.1016/j.lwt.2019.01.024
• Alkyl C-H confidence 1.0

  “Additionally, the spectrum of the CMC sample shows the following absorption bands: The cm-1was band located at about 2980 assigned for C-H stretching vibrations.”

  Ahmed 等 - 2021 - STRUCTURAL AND OPTICAL CHARACTERISTICS OF POLY(VIN DOI: 10.4314/bcse.v35i3.12
• Alkyl C-H confidence 1.0

  “The FTIR spectra of GaO x/SiO (Figure 6) held two sharp absorption bands in the 2 The FTIR spectra of GaOx/SiO2 (Figure 6) held two sharp absorption bands in the Ccm-1 C-H stretching region at 2980 and 2921 which can be attributed to [ νasC”

  Synthesis of High Surface Area—Group 13—Metal Oxides via Atomic Layer Deposition on Mesoporous Silica DOI: 10.3390/nano12091458
• Ester confidence 1.0

  “Polyacrylic Resins (AC 012, AC 013, AC P1 and AC 32) For the polyacrylic resins (AC 012, AC 013, AC P1 and AC 32), the IR spectra had cm-1, the characteristic signal at 1727 which was assigned to the stretching carbonyl ester cm-1 vibration”

  A Multidisciplinary Approach in Examining the Susceptibility to Microbial Attack of Polyacrylic and Polyurethane Resins Used in Art Restoration DOI: 10.3390/ijms231911725
• Alkyl C-H confidence 1.0

  “Pure PVP of high molecular weight (K30) shows the most intense and state of PVP, are located in the range 2822-2830, 2875-2890, and 2940-2980 cm-1 cm-1 CH stretching bands in the Raman spectrum at 2880, 2930 and 2980 [25].”

  Electrospun Fibres of Chitosan/PVP for the Effective Chemotherapeutic Drug Delivery of 5-Fluorouracil DOI: 10.3390/chemosensors9040070