What absorbs at 1388 cm⁻¹ in an FTIR spectrum?
A band near 1388 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 1388 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 | 7 | 6 | 1.0 |
| Methacrylate | 6 | 6 | 1.0 |
| Acetate | 6 | 6 | 1.0 |
| Methoxy (OCH3) | 4 | 4 | 1.0 |
| C-O single bond | 3 | 3 | 1.0 |
| Carboxyl (COOH) | 3 | 3 | 1.0 |
| Amide | 3 | 3 | 1.0 |
| C c single bond | 2 | 2 | 1.0 |
| Methyl | 2 | 2 | 1.0 |
| Ketone | 2 | 2 | 1.0 |
| Ester | 2 | 2 | 1.0 |
| Carbonyl (C=O) | 2 | 2 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| Nitrogen heterocycle | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 1.0 |
| Lipid | 1 | 1 | 1.0 |
| Thiol | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 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 |
|---|---|---|---|
| ZnO NPs | 1388, 1664, 875 | Alkyl C-H, Methacrylate, Acetate | 1 |
| ZnO | 1388, 1400, 3430 | Alkyl C-H, Acetate, Methacrylate | 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 1388 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
-
Amide confidence 1.0
“Larvicidal Property of Green Synthesized Silver Nanoparticles against Vector Mosquitoes 5 cm(cid:1)1), production would be an appropriate for extending the biologstretching 1388.16 aliphatic amine group (C-N stretchcm(cid:1)1), ical route f”
Larvicidal property of green synthesized silver nanoparticles against vector mosquitoes (Anopheles stephensi and Aedes aegypti) DOI: 10.1016/j.jksus.2015.10.006 -
Thiol confidence 1.0
“νas(COO-) cm-1 observed for the peak of asymmetric stretching vibrations = 1567 together with a cm-1 νs(COO-) cm-1, low-frequency shift by 3-5 for symmetric stretching vibrations = 1388 probably caused by the interaction of thiol with the A”
Kondratenko 等 - 2020 - Thioglycolic Acid FTIR Spectra on Ag2S Quantum Dot DOI: 10.3390/ma13040909 -
Carboxyl (COOH) confidence 1.0
“The peaks at 1388 correspond to symmetric and asymmetric stretching of carboxyl group (C=O).”
Pandey 等 - 2016 - Deposition and Characterization of AlZnO Thin Fil DOI: 10.1007/s11664-016-4750-8 -
Acetate confidence 1.0
“FTIR spectrum showed the high intensity broad band around 3416 The cm-1 intense broad band at 1388 and 1491 indicate the presence C=O stretching and C-C stretching of alkanes.”
Ecotoxicity of Musa paradisiaca leaf extract-coated ZnO nanoparticles to the freshwater microcrustacean Ceriodaphnia cornuta DOI: 10.1016/j.limno.2017.09.004 -
Alkyl C-H confidence 1.0
“The bands at 1388 and 1366 refer to an isopropyl (-C(CH 3) 2) group due to CH and CH bending, while the C-O asymmetric 2”
HPTLC and ATR/FTIR Characterization of Antioxidants in Different Rosemary Extracts DOI: 10.3390/molecules26196064 -
Alkyl C-H confidence 1.0
“In particular, the second derivative spectra of NI cells are characterized by a band at ~1468 cm-1 due to CH2/CH3 deformations of lipid hydrocarbon chains, two components at cm-1 ~1468 due to CH 2/CH deformations of lipid hydrocarbon chains”
Pathological ATX3 Expression Induces Cell Perturbations in E. coli as Revealed by Biochemical and Biophysical Investigations DOI: 10.3390/ijms22020943 -
Acetate confidence 1.0
“The peak at 1388 cm-1 vibration peak of the C-O bond in C-OH.”
Inhibition of Poly(ethylenediaminetetraacetic acid-diethanolamine) on Deposition of Calcium Sulfate Crystal in Simulated Industrial Water DOI: 10.3390/cryst10060544 -
Alkyl C-H confidence 1.0
“C=C 1626 Conjugated alkene Medium stretching C-H 1388 Aldehyde Medium bending C-O 1050 Primary alcohol Strong stretching”
Chowdhury 等 - 2023 - Green synthesis and characterization of zirconium DOI: 10.1016/j.heliyon.2022.e12711
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