What absorbs at 2780 cm⁻¹ in an FTIR spectrum?
A band near 2780 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 4 cited sources
Possible functional-group assignments
| Functional group | Supporting facts | Cited sources | Top confidence |
|---|---|---|---|
| Alkyl C-H | 2 | 2 | 1.0 |
| Hydroxyl (O-H) | 2 | 2 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
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
“4a, one can see clearly the strong absorption band cm-1 in the one-phonon region below 1500 and the huge CH stretching band between 2780 and cm-1 3100 in the three-phonon region without having any noticeable ripple effect.”
Investigation of bonded hydrogen defects in nanocrystalline diamond films grown with nitrogen/methane/hydrogen plasma at high power conditions DOI: 10.1016/j.jcrysgro.2016.12.050 -
Hydroxyl (O-H) confidence 1.0
“around 2780 The large peak represents the O-H groups in cellulose.”
Investigation of Hemp and Flax Fiber-Reinforced EcoPoxy Matrix Biocomposites: Morphological, Mechanical, and Hydrophilic Properties DOI: 10.3390/polym14214530 -
confidence 1.0
“For the chitosan films there was a cm-1 broad band ranging from around 3200 to 3300 which was attributed to the stretching cm-1 vibration of N-H and hydrogen-bonded hydroxyl groups, and the peak at 2780 was Polymers 2022, 14, x 9 of 21”
Physicochemical, Mechanical, and Structural Properties of Bio-Active Films Based on Biological-Chemical Chitosan, a Novel Ramon (Brosimum alicastrum) Starch, and Quercetin DOI: 10.3390/polym14071346 -
confidence 0.9
“Text: 'vibrations of C-H in O=C-H (2720 and 2780 the stretching vibrations)'”
Thermal behavior, decomposition mechanism and some physicochemical properties of starch-g-poly(benzyl acrylate) copolymers DOI: 10.1007/s10973-016-5603-7
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