What absorbs at 773 cm⁻¹ in an FTIR spectrum?
A band near 773 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
Quick answer
A band near 773 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 |
|---|---|---|---|
| Silicon-oxygen (Si-O) | 3 | 3 | 1.0 |
| Siloxane (Si-O-Si) | 2 | 2 | 1.0 |
| Silicon (Si) | 2 | 2 | 1.0 |
| Alkyl C-H | 2 | 2 | 1.0 |
| Silicon silicon | 1 | 1 | 1.0 |
| Metal oxygen | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| N-O bond | 1 | 1 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 1.0 |
| Alkene (C=C) | 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 |
|---|---|---|---|
| biochar | 773, 1640, 1115 | Alkyl C-H | 1 |
| activated carbon | 773, 1575, 1210 | 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 773 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
-
Silicon (Si) confidence 1.0
“Strong bands at 759cm-1 773cm-1 - was observed for LBGF glass respectively which attributes to (Si-O-Si) symmetric stretching The shift in band positions for LBGF glass can be observed as the [15].”
Development of Eu3+ doped Li2O-BaO-GdF3-SiO2 oxyfluoride glass for efficient energy transfer from Gd3+ to Eu3+ in red emission solid state device application DOI: 10.1016/j.jlumin.2018.07.009 -
Alkyl C-H confidence 1.0
“LLM confirmed rule peak-group candidate”
Study of biochar from pyrolysis and gasification of wood pellets in a nitrogen plasma reactor for design of biomass processes DOI: 10.1016/j.jece.2019.103391 -
Phosphate (PO4) confidence 1.0
“~ 633 Bending vibrations of V-O bonds ~724 (Q1) ~ 762 Stretching vibrations of P-O-P bonds ~ 773 (Q0) ~ 908 Bending vibrations of P-O-P bonds”
Andronache 和 Racolta - 2014 - Structural Investigation of MO center dot P2O5 cen DOI: 10.1063/1.4903024 -
N-O bond confidence 1.0
“Solutions of Al(NO but no bands at 773 or 790 3) 2O mixed with from [Al-HC(O)O] are formed”
Embrechts 等 - 2020 - In situ Raman and FTIR spectroscopic study on the DOI: 10.1039/c9ra09968a -
Alkyl C-H confidence 1.0
“cm-1, cm-1, The presence of the amorphous and crystalline matrix The peak value obtained at 1026.76 773.11 cm-1 before and after adsorption was assessed by X-ray difand 512.18 indicates the presence of Alkyl ketone, fraction, as shown in Fi”
Optimization of Cr (VI) removal from aqueous solution with activated carbon derived from Eichhornia crassipes under response surface methodology DOI: 10.1186/s13065-023-00913-6 -
confidence 1.0
“ESI-MS molecular-ion peak 773.21, corresponding to H+ + 1H [Zn(L1) ].”
Gusev 等 - 2020 - Synthesis, Photoluminescence and Electrical Study DOI: 10.3390/ma13245698 -
Metal oxygen confidence 1.0
“A peak at x cm-1 773 was observed for the SnO-EtOH and SnO-MeOH films, which corresponds to a O-Sn-O cm-1 bond.26 2 The peak attained at around 960 for SnO-EtOH and SnO-MeOH thin films and 5”
Marikkannan 等 - 2015 - A novel synthesis of tin oxide thin films by the s DOI: 10.1063/1.4909542 -
Silicon-oxygen (Si-O) confidence 1.0
“LLM confirmed rule peak-group candidate”
A diamino-functionalized silsesquioxane pillared graphene oxide for CO2 capture DOI: 10.1039/d1ra00777g
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