What absorbs at 681 cm⁻¹ in an FTIR spectrum?
A band near 681 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 5 cited sources
Quick answer
A band near 681 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.
Possíveis atribuições de grupos funcionais
| Grupo funcional | Fatos de suporte | Fontes citadas | Maior confiança |
|---|---|---|---|
| Hydroxyl (O-H) | 2 | 2 | 1,0 |
| Metal oxygen | 1 | 1 | 1,0 |
| Methyl | 1 | 1 | 1,0 |
| Methoxy (OCH3) | 1 | 1 | 1,0 |
| Methacrylate | 1 | 1 | 1,0 |
| Alkyl C-H | 1 | 1 | 1,0 |
| Acetate | 1 | 1 | 1,0 |
| Silicon (Si) | 1 | 1 | 1,0 |
| Metalloid oxygen | 1 | 1 | 0,7 |
A classificação reflete a evidência acumulada da literatura, não uma única regra autoritária. Sempre confirme com o contexto da sua amostra.
Possible materials
| Material | Picos de suporte | Overlapping groups | Fontes citadas |
|---|---|---|---|
| calcite | 681, 2850, 2864 | Methoxy (OCH3), Hydroxyl (O-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 681 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.
Literatura por trás destas atribuições
-
Silicon (Si) confiança 1,0
“Furthermore, the relatively large new absorption 680.8 3.09 3.07 3.19 3.12 0.06 related to the Si-(CH 3) vibration is essentially unaffected 3”
Chalasani 等 - 2013 - A Spectroscopic Method for Hydroxyl Value Determin DOI: 10.1007/s11746-013-2334-9 -
Metal oxygen confiança 1,0
“stretchingandN-Hbendingvibrationrespectively.FTIRanalcm-1 ysis of MIONPs demonstrated a band at 681 corroborat850To further characterize the phase, orientation and grain size of ing the Fe-O-Fe stretching vibration in the region of cm-1 syn”
Removal of Cr(VI) by magnetic iron oxide nanoparticles synthesized from extracellular polymeric substances of chromium resistant acid-tolerant bacterium Lysinibacillus sphaericus RTA-01 DOI: 10.1007/s40201-019-00415-5 -
Hydroxyl (O-H) confiança 1,0
“1100, 1070, (Si-Ostretching) and 800, 681cm-1 (R-O-H bending, where R is the octahedral ion - peninsula, makes it possible to draw important conclusions.”
Zorba 等 - 2006 - Technique and palette of XIIIth century painting i DOI: 10.1007/s00339-006-3548-6 -
Hydroxyl (O-H) confiança 1,0
“2 bands at 1409 cm-1 (ν3 asymmetric stretching), 1045 cm-1 (ν1 symmetric stretching), 839 cm-1 (ν2 outcm-1 ν bending), the split in the in-plane bending vibration at 690 and 681 and the OH stretching 4 in-plane bending vibration at 690 and”
Investigating the Potential of the Er:YAG Laser for the Removal of Cemented Dust from Limestone and Painted Plaster DOI: 10.3390/coatings10111099 -
Metalloid oxygen confiança 0,7
“Peak at 681 cm-1 associated with Ge bridging oxygen signatures.”
Santos 等 - 2007 - Vibrational spectroscopy study of niobium germanos DOI: 10.1016/j.jnoncrysol.2007.02.018
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