What absorbs at 632 cm⁻¹ in an FTIR spectrum?
A band near 632 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 632 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) | 9 | 9 | 1.0 |
| Metal oxygen | 3 | 3 | 1.0 |
| Carbohydrate | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| Perchlorate | 1 | 1 | 0.9 |
| Phosphate (PO4) | 1 | 1 | 0.8 |
| C-S single bond | 1 | 0 | 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 |
|---|---|---|---|
| SnO2 | 632, 2800, 1547 | Metal oxygen, Hydroxyl (O-H) | 2 |
| Hydroxyapatite | 632, 1620, 1639 | Hydroxyl (O-H) | 2 |
| Nanoparticles | 632, 1732, 1647 | Hydroxyl (O-H), Metal oxygen | 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 632 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
-
Metal oxygen confidence 1.0
“The band at 632 was strongly O-Sn-O combine with antisymmetric stretching mode bridge of SnO2 cm(cid:0) cm(cid:0) 1 1 functional groups.”
Structural, optical, electrical and magnetic properties of Cu and Ni doped SnO2 nanoparticles prepared via Co-precipitation approach DOI: 10.1016/j.physb.2020.412169 -
Metal oxygen confidence 1.0
“A small shift was detected toward lower cm-1 cm-1 wavenumbers position of O-Sn-O peak from 632.5 in pure tin oxide to 618 for the sample prepared with 4% Ti doping content.”
High Efficient and Cost Effective Titanium Doped Tin Dioxide Based Photocatalysts Synthesized via Co-precipitation Approach DOI: 10.3390/catal11070803 -
Alkene (C=C) confidence 1.0
“Importantly, the characteristic peak of the monomer double bond at 1,632cm-1(C0Cstretching)disappeared.Thisconfirmedthat the polymerization of vinyl monomers occurred.”
Taenghom 等 - 2013 - Synthesis and characterization of nano-sized poly[ DOI: 10.1007/s00396-012-2867-8) -
Ring structure confidence 1.0
“The peak cm-1 at 632 is associated with bending vibrations of the ring [32].”
Enhancing the Thermal Stability of Ionogels: Synthesis and Properties of Triple Ionic Liquid/Halloysite/MCC Ionogels DOI: 10.3390/molecules26206198 -
Hydroxyl (O-H) confidence 1.0
“4 shows 7 the disappearance of OH bending at 632 cm-1 in the SHA series, which could be the effect of OH42replacing the group with SO ions to balance the charge on the HA surface.”
Alshemary 等 - 2023 - Microstructure analysis and thermal stability of M DOI: 10.15251/DJNB.2023.181.1 -
confidence 1.0
“However, a calcium-deficient cm-1 modes and the sharp peaks at 3573 and 632 are assigned to stretching and wagging vibrations of”
Zirconia/Hydroxyapatite Composites Synthesized Via Sol-Gel: Influence of Hydroxyapatite Content and Heating on Their Biological Properties DOI: 10.3390/ma10070757 -
Hydroxyl (O-H) confidence 1.0
“10 of 17 peaks from 632 and 3568 cm-1 are attributed to the vibrational (υL) and stretching (υs) vi- (OH-) group.”
Physicochemical Characterization of Europium-Doped Hydroxyapatite Thin Films with Antifungal Activity DOI: 10.3390/coatings12030306 -
Hydroxyl (O-H) confidence 1.0
“The bands at 632/3572 cm-1 43are assigned to liberational/str hing modes of hydroxyl groups and the bands near 3420 and 1635 cm-1 arise from the adsorbed water molecules [36].”
Engin 和 Girgin - 2009 - Synthesis of hydroxyapatite by using calcium carbo DOI: 10.2478/s11532-009-0063-6
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