What absorbs at 2947 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 2947 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 2947 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

  “High performance liquid terized as C-H stretching at frequency 2947 and 1456 chromatography in phytochemical analysis.”

  Chik 等 - 2011 - Predicting group of metabolites available in parti DOI: 10.5897/AJB11.2736
• Alkyl C-H confidence 1.0

  “LLM confirmed rule peak-group candidate”

  Sprayed in-situ synthesis of Polyvinyl alcohol/Chitosan loaded Silver nanocomposite hydrogel for improved antibacterial effects DOI: 10.1016/j.ijbiomac.2019.09.186
• Alkyl C-H confidence 1.0

  “Mannitol presented a cm-1 cm-1 sented a characteristic peak at ~3281 (-OH stretching vibration), ~2947 (C-H characteristic peak at ~3281cm-1 (-OH stretching vibration), ~2947 cm-1 (C-H stretching cm-1”

  Almotairi 等 - 2022 - Design and Optimization of Lornoxicam Dispersible DOI: 10.3390/ph15121463
• Alkyl C-H confidence 1.0

  “The -C-H stretching and cm-1, group, but there is not any significant difference between bending vibrations appeared at 2947 and 1442 respecST-5 and ST-c.”

  Ayaz 等 - 2013 - The effect of acrylamide incorporation on the ther DOI: 10.4047/jap.2013.5.2.110
• Acetate confidence 1.0

  “When analyzing cellular lipid profiles based on FTIR spectra, the most important lipid associated peaks usually taken into consideration are the following: (1) the peaks 2947 cm-1, 2925 cm-1, 2855 cm-1, 1465 cm-1 and 1377 cm-1 are related t”

  Byrtusova 等 - 2020 - Revealing the Potential of Lipid and beta-Glucans DOI: 10.3390/microorganisms8071034
• Acetate confidence 1.0

  “Spectrum of GZ showed prominent -OH cm-1, C-H stretching band at stretching band at 3223.05 cm-1, cm-1 2875.86 and -C=O stretching peak 2947.23 cm-1, C=C stretching vibration at 1656.85 at 1722.43”

  Harwansh 和 Deshmukh - 2021 - Formulation and Evaluation of Sodium Alginate and DOI: 10.5530/ijper.55.3.145
• Alkyl C-H confidence 1.0

  “3296 cm-1 (OH vibration), 2947 cm-1 (asymmetrical CH stretching vibration), 2875 cm-1 cm-1 Figure 2.”

  Morphology and Selected Properties of Modified Potato Thermoplastic Starch DOI: 10.3390/polym15071762
• Alkyl C-H confidence 1.0

  “- - 2947 -CH stretching 2947 -CH stretching”

  Argon and Argon–Oxygen Plasma Surface Modification of Gelatin Nanofibers for Tissue Engineering Applications DOI: 10.3390/membranes11010031