What absorbs at 2750 cm⁻¹ in an FTIR spectrum?
A band near 2750 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 7 cited sources
Quick answer
A band near 2750 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
| Functional group | Supporting facts | Cited sources | Top confidence |
|---|---|---|---|
| Alkyl C-H | 4 | 4 | 1.0 |
| Alkene (C=C) | 2 | 2 | 1.0 |
| Hydrogen bond | 1 | 1 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
Ranking reflects accumulated literature evidence, not a single fixed rule. Always confirm against your sample context.
Possible materials
| Material | Supporting peaks | Overlapping groups | Cited sources |
|---|---|---|---|
| Cellulose | 2750, 1735, 1650 | Alkyl C-H, Carbohydrate | 1 |
| cells | 2750, 970, 1741 | Alkyl C-H | 1 |
| poly(vinyl alcohol) | 2750, 1700, 2993 | Alkyl C-H | 1 |
| PMMA | 2750, 1722, 1383 | Alkyl C-H | 1 |
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 2750 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
“The integrated intensity of the SiH (between 2200 and x 2000cm-1) 2750cm-1) and CH (between 3050 and absorpx tion bands will be the tool to evaluate the PS modification as”
Giovannozzi 和 Rocchia - 2008 - Effect of the reaction time, reagent concentration DOI: 10.1016/j.snb.2007.10.043 -
Hydroxyl (O-H) confidence 1.0
“In the region of 2750 O-H binding bands were identified.”
Development of an Epoxy Matrix Hybrid Composite with Astrocaryum Aculeatum (Tucumã) Endocarp and Kaolin from the Amazonas State in Brazil DOI: 10.3390/polym15112532 -
Alkene (C=C) confidence 1.0
“2750 and a band assigned to an olefinic =CH 2 cm-1.”
Mcnab 等 - 2017 - Quantification and qualification by in-situ FTIR o DOI: 10.1016/S0926-860X(99)00160-X. -
Alkyl C-H confidence 1.0
“As far as the high-frequency region of the spectra is concerned, the band between ~2750 cm-1 and ~3000 cm-1 was assigned to the CH and CH2 symmetrical stretching arising from both cellulose and bPEI chains.”
2D Correlation Spectroscopy (2DCoS) Analysis of Temperature-Dependent FTIR-ATR Spectra in Branched Polyethyleneimine/TEMPO-Oxidized CelluloseNano-Fiber Xerogels DOI: 10.3390/polym13040528 -
Alkene (C=C) confidence 1.0
“2 Effect of AHP on PBMCs FTIR spectra (a) in the region 2750 to (arrow indicates band at corresponding to olefinic cm-1 cm-1 ∼1740 1800 (arrow indicates band at corresponding to esters).”
Sahu 等 - 2013 - Study of plasma-induced peripheral blood mononucle DOI: 10.1117/1.JBO -
Hydrogen bond confidence 1.0
“3 and macrocycle (2960, 2925, 1470, 1209 The absence of free S-H bonds vibrations at cm-1 cm-1 ν ν = 2750 as well as the presence of SS bonds vibrations at = 640 [50] in the 3, fingerprint region, which did not appear in the initial macrocy”
Self-Healing Thiolated Pillar[5]arene Films Containing Moxifloxacin Suppress the Development of Bacterial Biofilms DOI: 10.3390/nano -
Alkyl C-H confidence 1.0
“cm-1 the A new peak with low intensity at 2750 was ascribed to the symmetric stretching of C-H cm-1 cm-1, 347.”
UV-shielding properties of a cost-effective hybrid PMMA-based thin film coatings using TiO2 and ZnO nanoparticles: a comprehensive evaluation DOI: 10.1038/s41598-023-34120-z
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