What absorbs at 3570 cm⁻¹ in an FTIR spectrum?
A band near 3570 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 3570 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 |
|---|---|---|---|
| Hydroxyl (O-H) | 22 | 20 | 1.0 |
| Alkyl C-H | 1 | 1 | 1.0 |
| Silicon hydride | 1 | 1 | 1.0 |
| Silicate | 1 | 1 | 1.0 |
| Phosphate (PO4) | 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 |
|---|---|---|---|
| hydroxyapatite | 3570, 1620, 1639 | Hydroxyl (O-H), Alkyl C-H | 2 |
| polyvinyl alcohol | 3570, 1141, 1640 | Hydroxyl (O-H), Alkyl C-H | 1 |
| calcium phosphate | 3570, 1070, 1149 | Hydroxyl (O-H), 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 3570 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
-
Hydroxyl (O-H) confidence 1.0
“cm21) n and the phosphate hydroxyl OH peak (3570 One major peak is observed, confirming the presence of 3 cm21) stretching vibration (1030 for the acid were a unique phosphorus environment, that of the allyl”
Phillips 等 - 2005 - Surface modification of bioceramics by grafting of DOI: 10.1179/174367605X62436 -
Hydroxyl (O-H) confidence 1.0
“This cm-1 cm-1 study shows the presence of hydroxyl (OH) stretch mode bands at ~3570 (Fig.”
Toibah 等 - 2012 - FTIR Study on Phase Behavior of Magnesium-doped Bi DOI: 10.1063/1.4732476 -
Hydroxyl (O-H) confidence 1.0
“In the stretching band, lower cm-1 reveals associating hydroxyl groups in hydrogen 3570 cm-1 bonds, and higher 3570 reveals free hydroxyl groups in amorphous region.”
Xue 等 - 2015 - Moving-window two-dimensional correlation infrared DOI: 10.1007/s00216-015-9035-1 -
Hydroxyl (O-H) confidence 1.0
“LLM confirmed rule peak-group candidate”
Investigation of the effect of doped Zn atom to the hydroxyapatite based on experimental method and first-principles calculations DOI: 10.1007/s41779-019-00430-7 -
Hydroxyl (O-H) confidence 1.0
“Notably, the spectrum of cm-1, (OH)- undoped HAp shows a well-resolved sharp peak at 3570 due to the stretching mode of the undoped HAp shows a well-resolved sharp peak at 3570 cm-1, due to the stretching mode of the (OH)-”
Baldassarre 等 - 2020 - Crystal Chemistry and Luminescence Properties of E DOI: 10.3390/cryst10040250 -
Hydroxyl (O-H) confidence 1.0
“The well resolved vibration band at 3570 cm-1 indicates the presence of isolated and twin O-H groups from the hydroxyapatite structure (Rapacz-Kmita et al., 2005).”
Broda 等 - 2019 - Synthesis and selected physicochemical properties DOI: 10.5277/ppmp19073 -
Phosphate (PO4) confidence 1.0
“OHcm-1) Simultaneous decay of the vibrational modes of ions HA (3570 indicates the substitution of 43ОН44- phosphates for silicates with the hydroxyl groups involved: РО + SiO + that agrees ОН with the literature data [1, 9-13].”
Golovanova 等 - 2016 - Study of thermal effects of silicate-containing hy DOI: 10.1088/1757-899X/110/1/012024 -
Hydroxyl (O-H) confidence 1.0
“OHbonds 3506cm-1 OHstretching(free) StretchingO-H 3524/28/42cm-1 StretchingO-H 3570/77/78/82/90/9cm-1 O-H&N-Hstretchingvibrations 3611cm-1”
Phytochemical screening, polyphenols, flavonoids and tannin content, antioxidant activities and FTIR characterization of Marrubium vulgare L. from 2 different localities of Northeast of Morocco DOI: 10.1016/j.heliyon.2020.e05609
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