What absorbs at 1377 cm⁻¹ in an FTIR spectrum?
A band near 1377 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 1377 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 | 32 | 29 | 1.0 |
| Methacrylate | 8 | 8 | 1.0 |
| Acetate | 8 | 8 | 1.0 |
| Methoxy (OCH3) | 7 | 7 | 1.0 |
| C-O single bond | 5 | 5 | 1.0 |
| Methyl | 5 | 4 | 1.0 |
| Amide | 4 | 4 | 1.0 |
| Carbohydrate | 4 | 4 | 1.0 |
| Hydrogen bond | 3 | 3 | 1.0 |
| Hydroxyl (O-H) | 3 | 3 | 1.0 |
| Carboxyl (COOH) | 3 | 2 | 1.0 |
| Alkene (C=C) | 3 | 2 | 1.0 |
| Aromatic ring | 2 | 2 | 1.0 |
| Carbonyl (C=O) | 2 | 2 | 1.0 |
| Aldehyde (CHO) | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Ring structure | 1 | 1 | 1.0 |
| C=n | 1 | 1 | 1.0 |
| N-O bond | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Ketone | 1 | 1 | 1.0 |
| Ester | 1 | 1 | 1.0 |
| C c single bond | 1 | 1 | 1.0 |
| Carbonate | 1 | 1 | 0.9 |
| Phospholipid | 1 | 1 | 0.7 |
| Nucleic acid | 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 |
|---|---|---|---|
| bitumen | 1377, 1625, 810 | Alkyl C-H | 1 |
| Silver nanoparticles | 1377, 1636, 1631 | Alkyl C-H, 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 1377 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 c single bond confidence 1.0
“The stretching vibrations of C-C occur at 1377 1184 1128 5 cm-1.”
Crystal Growth, Spectral, Optical, Laser damage, Photoconductivity and Dielectric Properties of Semiorganic L-cystine hydrochloride Single Crystal DOI: 10.1016/j.saa.2015.06.113 -
Alkyl C-H confidence 1.0
“Sharp CH measurements (B 2 cm-1 cm-1 in B and 1379 in B seen that the cellulose content in outer and inner fibers are intense band at 1377 in out represents C-H asymmetric deformation in cellulose [53].”
Das 等 - 2017 - Extraction of xylem fibers from Musa sapientum and DOI: 10.1007/s12221-017-1187-5 -
Acetate confidence 1.0
“vibration at 3410.69 which corresponds to the O-H stretching vibration, 2924.78 which corresponds to C-H stretching vibration, and 1377.13 corresponds to C=O asymmetric stretching vibration.”
Geetha 等 - 2020 - Nano zinc oxide - An alternate zinc supplement for DOI: 10.14202/vetworld.2020.121-126 -
Alkyl C-H confidence 1.0
“2 cm-1 COOcm-1 1402 for C=O symmetric stretching of groups and the band at 1377 for C-H bending cm-1-”
Gupta 等 - 2022 - In vitro cell composition identification of wood d DOI: 10.1098/rsos.201935 -
Alkyl C-H confidence 1.0
“∼1377cm-1 shows the CH bending in paraffin oil.”
Synthesis and size dependent optical studies in CdSe quantum dots via inverse micelle technique DOI: 10.1016/j.matchemphys.2010.06.053 -
Acetate confidence 1.0
“The band ~ 1377 from the anatase matrix is shifted after cm-1 encapsulation and appeared around 1397 probably due to the C-O-C stretching vibration cm-1 [26, 27].”
Fast responsive anatase nanoparticles coated fiber optic pH sensor DOI: 10.1016/j.jallcom.2020.156246 -
Carbonyl (C=O) confidence 1.0
“Omairey, Zhang, Al-Malaika, Sheena, Gu cm-1 Peak 1377 has been chosen as a reference due to its relatively compatible height 268 compared to the carbonyl peak, which causes fewer errors.”
Omairey 等 - 2019 - Impact of anti-ageing compounds on oxidation agein DOI: 10.1016/j.conbuildmat.2019.07.021 -
N h confidence 1.0
“CAH assigned to the bend of CH 2/CH arene-ethylbenzene, the 3 cm(cid:1)1 peak of 1377 was correlated as C-X fluoride, the peak cm(cid:1)1 cm(cid:1)1 CAN 1281 corresponded to amines.”
Green synthesis of Silver nanoparticles using Streptomyces hirsutus strain SNPGA-8 and their characterization, antimicrobial activity, and anticancer activity against human lung carcinoma cell line A549 DOI: 10.1016/j.sjbs.2021.08.084
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