What absorbs at 1375 cm⁻¹ in an FTIR spectrum?
A band near 1375 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 1375 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 | 50 | 46 | 1.0 |
| Methoxy (OCH3) | 16 | 16 | 1.0 |
| Methacrylate | 16 | 16 | 1.0 |
| Acetate | 16 | 16 | 1.0 |
| Methyl | 15 | 14 | 1.0 |
| Hydroxyl (O-H) | 13 | 13 | 1.0 |
| C-O single bond | 9 | 9 | 1.0 |
| Amide | 6 | 6 | 1.0 |
| C n single bond | 5 | 5 | 1.0 |
| Alkene (C=C) | 4 | 4 | 1.0 |
| Carbohydrate | 4 | 4 | 1.0 |
| Secondary amine | 4 | 4 | 1.0 |
| Sulfate (SO4) | 2 | 2 | 1.0 |
| Silicon-oxygen (Si-O) | 2 | 2 | 1.0 |
| Ester | 2 | 2 | 1.0 |
| Borate | 2 | 2 | 1.0 |
| Carboxyl (COOH) | 2 | 2 | 1.0 |
| Aromatic ring | 2 | 1 | 1.0 |
| Chitosan | 1 | 1 | 1.0 |
| Acetyl | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Siloxane (Si-O-Si) | 1 | 1 | 1.0 |
| Silicon (Si) | 1 | 1 | 1.0 |
| S eq o | 1 | 1 | 1.0 |
| Phosphorus | 1 | 1 | 1.0 |
| Phosphate (PO4) | 1 | 1 | 1.0 |
| C-S single bond | 1 | 1 | 1.0 |
| Amino acid | 1 | 1 | 1.0 |
| Phenolic | 1 | 1 | 0.9 |
| Carbonate | 1 | 1 | 0.9 |
| C c 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 |
|---|---|---|---|
| CdS | 1375, 1092, 1114 | Methoxy (OCH3), Methacrylate, Acetate | 1 |
| silver nanoparticles | 1375, 1636, 1631 | Alkyl C-H, Methacrylate, Acetate | 1 |
| microplastics | 1375, 1643, 1614 | Alkyl C-H, Methacrylate, Acetate | 1 |
| polyimide | 1375, 1720, 1778 | Methacrylate, Acetate | 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 1375 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
-
C n single bond confidence 1.0
“Nevertheless, the stretching vibrations of C=O cm-1, bond [34], C-O bond [34, 35] and C-N bond [35] are found at peak positions of 1740 1375 cm-1”
Aziz 等 - 2023 - Water remediation capability of cubic-phase CdS na DOI: 10.15251/DJNB.2023.181.203 -
Alkyl C-H confidence 1.0
“The PP showed reference peaks displayed at 972, 997, and 1165 cm-1 (-CH3 oscillating 3 -1 -1 oscillating vibrations), 1375 cm (-CH symmetric bending vibrations), 2952 cm (-CH”
Campanale 等 - 2023 - Fourier Transform Infrared Spectroscopy to Assess DOI: 10.3390/polym15040911 -
Alkyl C-H confidence 1.0
“The signal observed at 1457 and UV+IR IR radiation, and radiations was accomplished [19] 1375cm-1 can be assigned to CH and/or CH groups.”
Fernandez-Varela 等 - 2006 - Monitoring photooxidation of the Prestige's oil sp DOI: 10.1016/j.talanta.2005.10.006 -
Alkyl C-H confidence 1.0
“The peak at ~1375 is associated with cm-1 asymmetric vibrations of C-H band;”
Filipova 等 - 2018 - Synthesis of Nanofibrillated Cellulose by Combined DOI: 10.3390/nano8090640 -
confidence 1.0
“Imidization 100 ( A I ~ ~ ~ / A I S O I ) / ( A I ~ ~ S / A I ~ O I ) ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ C % x (1) = where and are the peak areas at 1375cm-' and 1501cmp1, A1501”
Ha 等 - 1998 - Polarized Infrared Spectroscopic Studies of Polari DOI: 10.1080/10587259808025380 -
Acetate confidence 1.0
“The percentage of could be identified as -C-O peak at 1375 and 1218 AgNPs loaded into the diatomite pore was measured using single bond absorption.”
Hamdiani 和 Shih - 2021 - A Green Method for Synthesis of Silver-Nanoparticl DOI: 10.22146/ijc.63573 -
Acetate confidence 1.0
“6b) at 1733, esterification process, the crystalline structure of the NCS is with cm-1 1252 assigned to carbonyl C O stretch vibration, CH 1375, destroyed.”
Synthesis, characterization and functional properties of low substituted acetylated corn starch DOI: 10.1016/j.ijbiomac.2012.02.030 -
Hydroxyl (O-H) confidence 1.0
“OH--stretching 1375 (b) Results of fitting of the vibration;”
Tobelite and NH4+-rich muscovite single crystals from Ordovician Armorican sandstones (Brittany, France): Structure and crystal chemistry DOI: 10.2138/am.2012.4023
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