What absorbs at 1304 cm⁻¹ in an FTIR spectrum?
A band near 1304 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 1304 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 | 4 | 4 | 1.0 |
| Methoxy (OCH3) | 2 | 2 | 1.0 |
| Methacrylate | 2 | 2 | 1.0 |
| C-O single bond | 2 | 2 | 1.0 |
| Acetate | 2 | 2 | 1.0 |
| Amine primary | 2 | 2 | 1.0 |
| Protein | 1 | 1 | 1.0 |
| Aromatic ring | 1 | 1 | 1.0 |
| Secondary amine | 1 | 1 | 1.0 |
| C n single bond | 1 | 1 | 1.0 |
| Amide | 1 | 1 | 1.0 |
| N h | 1 | 1 | 1.0 |
| Hydroxyl (O-H) | 1 | 1 | 0.9 |
| Carbonyl (C=O) | 1 | 1 | 0.9 |
| C c single bond | 1 | 1 | 0.9 |
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 |
|---|---|---|---|
| polypropylene | 1304, 1030, 1600 | Alkyl C-H, Methacrylate, Methoxy (OCH3) | 1 |
| methane | 1304, 1740, 1400 | Alkyl C-H, 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 1304 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
-
Alkyl C-H confidence 1.0
“LLM confirmed rule peak-group candidate”
Structural Dependence and Spectroscopic Evidence of Methane Dissolution in Ionic Liquids DOI: 10.1021/acs.jpcb.8b03178 -
Amine primary confidence 1.0
“In the second more, the peaks at 1304, 758 and 722, and cm(cid:1)1 reaction, the oligoamide was further 593 are assigned to primary amine, N-C¼O reacted with urea to yield a urea oligoasecondary amide, and of amide mide, referred to in this”
Synthesis of Sunflower Oil Based Elastomer and Its Characterization by Using Spectroscopic Techniques DOI: 10.1002/masy.201550322 -
Acetate confidence 1.0
“cm-1 At wave number 1304 is C-O stretching, and 1030 Table 1.”
Composites polyvinyl alcohol filled with nanocellulose from oil palm waste by formic acid hydrolysis DOI: 10.1051/matecconf/201926804012 -
Alkyl C-H confidence 1.0
“3 cm-1 cm-1, 1304 corresponds to CH vibrations;”
From Waste to Potential Reuse: Mixtures of Polypropylene/Recycled Copolymer Polypropylene from Industrial Containers: Seeking Sustainable Materials DOI: 10.3390/su14116509 -
Amide confidence 1.0
“A cm-1 new peak at 1651.07 represented the formation of charged aromatic amine derivatives, cm-1 whereas peak at 1303.88 for C-N stretching vibration support formation of aromatic”
Cossolin 等 - 2019 - DOI: 10.4136/1980-993X -
Alkyl C-H confidence 1.0
“Explicit assignment: 'absorption of CH gave rise to peaks at 1304'.”
Portable Combination of Fourier Transform Infrared Spectroscopy and Differential Mobility Spectrometry for Advanced Vapor Phase Analysis DOI: 10.1039/c8an01192c. -
Alkyl C-H confidence 1.0
“C-H in-plane vibration mode at 1304, 1170 and 1038 The incorporation of Co into PPy apparently suppressed the IR bands corresponding to C=C, C-N and C-H, implying 380”
Li 等 - 2008 - A Comparative Study of Co-PPy-MWCNTs as a Non-nobl DOI: 10.1149/1.2981872 -
Aromatic ring confidence 1.0
“1(a)} and it contains quinonoid (1582 benzenoid (1488 cm-1), cm-1), cm-1), C-N stretching (1304 aromatic stretching (817, 688 O-C stretching (1027 Ccm-1) cm-1).”
Mary 等 - 2023 - Synthesis, characterization and non-isothermal deg DOI: 10.21203/rs.3.rs-2849661/v1
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