What absorbs at 2970 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 2970 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 2970 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

  “graed Fig.1illustratesthefunctionalgroupsforPC,PC/FAC,PC/GFAC silane FAC which enhances the adherence properties cm(cid:1)1 by FTIR spectra, which displays a steep peak at 2970 for withtheinorganicPC.Thenoblestateofdistributionofpristine C”

  Thin film encapsulation of nano composites of polycarbonate (PC) for thermal management systems DOI: 10.1039/c4ra10183a
• Alkyl C-H confidence 1.0

  “45 46 The gas phase FTIR spectra of CH 3CN at 20 Torr (Figure 2A) shows major peaks at 2970, 2954, 47 48”

  Blue-Shifted Hydrogen Bonding in the Gas Phase CH/D3CN●●●HCCl3 Complexes DOI: 10.1021/acs.jpca.8b12200
• confidence 1.0

  “The peak at 796 is due to N-H wagging, 3 Results and discussion cm-1 cm-1 while peaks at 2970 and 3186 are due to N-H”

  Thakur 和 Lokhande - 2017 - Effect of dip time on the electrochemical behavior DOI: 10.1515/epoly-2016-0160
• Alkyl C-H confidence 1.0

  “On the other hand, for the NF270 PIP membrane, only a slight cm-1 C-H was reduction in the stretching peak at 2970 observed.3 3.3.”

  Van 等 - 2012 - Degradation of Polyamide Nanofiltration and Revers DOI: 10.1021/es203090y
• Alkyl C-H confidence 1.0

  “LLM confirmed rule peak-group candidate”

  Assessment of quality of commercial hand sanitizers using Fourier transform infrared spectroscopy and gas chromatography DOI: 10.1016/j.mex.2023.102274
• Alkyl C-H confidence 1.0

  “and combination groups of lower-frequency vibrations from -COOH function cm-1 Stretching of -CH groups appear at 2970 and 2888 also referring to a complex shape due to the existence of = CH, -CH 3, -CH and -CH bands, while the -CH groups di”

  Influence of gamma irradiation on rosin properties and its antimicrobial activity DOI: 10.1038/s41598-023-31372-7
• Alkyl C-H confidence 1.0

  “to 2970 and the CH band between 2905 and 2945 To further observe the relative lipid/protein content in”

  Biophysical Stress Responses of the Yeast Lachancea thermotolerans During Dehydration Using Synchrotron-FTIR Microspectroscopy DOI: 10.3389/fmicb.2020.00899
• Alkyl C-H confidence 1.0

  “1430 [48] α PVDF iley.com 2 /doi/10.1002/app.48907 2970 2970 CH symmetric vibrations 2972 [19] α PVDF 2 2970 2970 CH symmetric vibrations”

  Chipara 等 - 2020 - Spectroscopic investigations on PVDF-Fe2O3 nanocom DOI: 10.1002/app.48907