What absorbs at 2820 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 2820 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 2820 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

  “4(c), a cm-1 peak around 2820 can be roughly recognized as well, although the CH stretching band is very weak in intensity”

  Tang 等 - 2007 - A comparison study of hydrogen incorporation among DOI: 10.1016/j.tsf.2006.10.132
• Alkyl C-H confidence 1.0

  “The peak at 2820 is related to N center and there are CH stretch vibrations of the C-H bond in the N-CH group.”

  Titus 等 - 2006 - Nitrogen and hydrogen related infrared absorption DOI: 10.1016/j.tsf.2005.12.062
• Hydroxyl (O-H) confidence 1.0

  “observed at while peaks at 2820 and Amethyst is the purple color variety of Quartz due to the may be resulted due to O-H stretching vibrations or might presence of Fe impurities.”

  Ahmad 等 - 2021 - Spectroscopic Analysis for Harnessing the Quality DOI: 10.1155/2021/6629640
• Alkyl C-H confidence 1.0

  “It is also observed that the relative intensity of the two bands near 2976 and 2820 cm-1 (anti-symmetrical and symmetrical C-H stretching modes) increased with the content of 1,12-dodecanedioate (DD) in the (co)polyester backbone, as eviden”

  Isosorbide and 2,5-Furandicarboxylic Acid Based (Co)Polyesters: Synthesis, Characterization, and Environmental Degradation DOI: 10.3390/polym14183868
• Alkyl C-H confidence 1.0

  “The dissolution efficiency cm-1, show typical bands at 2820 due to C-H stretching, and (DE) of various solid dispersions was calculated [Table 1].”

  Jagdale 等 - 2011 - Preparation and Characterization of Metformin Hydr DOI: 10.4103/0975-1483.83758
• Alkyl C-H confidence 1.0

  “The existence of aldehydes was manifested by the bands at ~2820 and cm-1, 2720 which were associated with the C-H stretching vibrations;”

  Regular Polymeric Microspheres with Highly Developed Internal Structure and Remarkable Thermal Stability DOI: 10.3390/ma14092240
• Aromatic ring confidence 1.0

  “f cm-1 cm-1 cm-1 -C-H -C-H 2950 for aromatic stretching, 2819.95 for 2873.81 for aliphatic stretching, 1700 and 1627 cm-1”

  Manjare 等 - 2023 - Microwave-Assisted Rapid and Green Synthesis of Sc DOI: 10.1021/acsomega.2c05187
• Alkyl C-H confidence 1.0

  “peaks observed at 2819.95/cm are C-H stretch (aldehydes) and O-H stretch (carboxylic acids);”

  Usmani 等 - 2023 - Molecular Docking of Bacterial Protein Modulators DOI: 10.3390/molecules28020574