What absorbs at 2900 cm⁻¹ in an FTIR spectrum?
A band near 2900 cm⁻¹ can point to several functional groups. Below are the most likely assignments, ranked by how much published evidence supports each — every one traceable to literature (DOI) and cross-validated against our 130,000+ reference spectra and knowledge graph.
Backed by 8 cited sources
Possible functional-group assignments
| Functional group | Supporting facts | Cited sources | Top confidence |
|---|---|---|---|
| Alkyl C-H | 60 | 53 | 1.0 |
| Hydroxyl (O-H) | 4 | 4 | 0.9 |
| Methyl | 2 | 1 | 0.95 |
| Alkene (C=C) | 2 | 1 | 0.8 |
| Silicon carbon | 1 | 1 | 0.9 |
| Methoxy (OCH3) | 1 | 1 | 0.8 |
| Aromatic ring | 1 | 1 | 0.8 |
| Carbohydrate | 1 | 1 | 0.6 |
Ranking reflects accumulated literature evidence, not a single authoritative rule. Always confirm against your sample context.
Literature behind these assignments
-
Alkyl C-H confidence 1.0
“Text: 'CH group (2900 Vibration'”
Wang 等 - 2021 - Molecular Structure of Poplar Lignin Obtained by p DOI: 10.3390/ijms19020428 -
Alkyl C-H confidence 0.95
“Explicit assignment: 'C-H stretching vibration band at 2900 from the methyl and methylene groups'.”
Ping 等 - 2020 - Assessment of the Physico-mechanical, Thermal, and DOI: 10.1007/s10924-017-1011-8 -
Alkyl C-H confidence 0.95
“Text: 'C-H reveal peaks at 2880 and 2900 due to stretches from the alkyl component'.”
Thomas 等 - 2015 - One-step grafting of polymers to graphene oxide DOI: 10.1039/c5py01358e -
Silicon carbon confidence 0.9
“Explicit assignment in text: 'presence of Si-CH peaks at 2900'”
Bhagat 等 - 2007 - Rapid synthesis of water-glass based aerogels by i DOI: 10.1016/j.apsusc.2006.07.016 -
Alkyl C-H confidence 0.9
“Text states '2900 ... are associated with the C-H'.”
Daniel 等 - 2020 - Citric acid modified cellulose a cost effective a DOI: 10.1080/15567036.2020.1773963 -
Alkyl C-H confidence 0.9
“Peak at 2900 cm-1 assigned to C-H stretching vibrations.”
Kemas 等 - 2017 - Starch-based xerogels Effect of acetylation on Ph DOI: 10.1016/j.ijbiomac.2017.01.101 -
Alkyl C-H confidence 0.9
“Explicit assignment”
Khairuddin 等 - 2016 - FTIR studies on the effect of concentration of pol DOI: 10.1088/1742-6596/776/1/012053 -
Alkyl C-H confidence 0.9
“Explicitly stated: 'peak around 2800-2900cm-1'.”
Mhaisagar 等 - 2014 - Mechanical properties of surface modified silica l DOI: 10.1016/j.mee.2013.10.006
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