What absorbs at 1303 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 1303 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

Ranking reflects accumulated literature evidence, not a single authoritative rule. Always confirm against your sample context.

Possible materials

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 1303 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

  “(duetoasymmetricCH 3bendingmodeofthemethylgroupofproteins), 1303cm-1 1250cm-1 C-N Measured log Estimated log Peak areas (from bonding of the protein), and (from”

  Simple quantitative analysis of Escherichia coli K-12 internalized in baby spinach using Fourier Transform Infrared spectroscopy DOI: 10.1016/j.ijfoodmicro.2010.09.013
• Amide confidence 1.0

  “cm-1 (stretching), 3065 due to = C-H (aromatic stretching), 2984 and 2950 due to C-H cm-1 cm-1 (stretching), 1696 due to C=O (stretching vibration), 1615 and 1488 due to C=C cm-1 cm-1 (ring stretching), 1445 due to CH3 (stretching), 1303 an”

  Adam 等 - 2022 - Comparative Evaluation of Amlodipine Besylate Gene DOI: 10.14227/DT290422PGC2
• Alkyl C-H confidence 1.0

  “Methane was the second chemical species detected (-C-H with FTIR wavenumber assignments of 1303 and 3015 cm-1, [29,36]).”

  Structural and Thermoanalytical Characterization of 3D Porous PDMS Foam Materials: The Effect of Impurities Derived from a Sugar Templating Process DOI: 10.3390/polym10060616
• Alkyl C-H confidence 1.0

  “(C-N bending) (e, f), 1735 (CO stretching) (d), 1450 and 1368 (CH stretching), 1573 stretching), 1504 (amide II), 1446 2 1234and1071cm-1(C-Ostretching)(g,h).Thechromaticscaleof cm-1 (CH bending), and 1303 (HCC stretching) cm 2 each map qual”

  Assessment of microplastic pollution: occurrence and characterisation in Vesijärvi lake and Pikku Vesijärvi pond, Finland DOI: 10.1007/s10661-019-7843-z
• Amide confidence 1.0

  “Pathological examinations with C-H, (lipid) 1400 C-O-H hematoxylin and eosin (H&E) staining were performed in 𝛿 𝛿 C-H, C-O-H, and amide III band 1303 all fifty-six samples.”

  Yao 等 - 2014 - The Use of FTIR-ATR Spectrometry for Evaluation of DOI: 10.1155/2014/213890
• Carboxyl (COOH) confidence 0.9

  “Text: 'two additional peaks at 1303 and 539 are COO- obse' (likely 'observed')”

  Marudhu 等 - 2022 - Influence of L-alanine doping on zinc (IRIS) thiou DOI: 10.21203/rs.3.rs-1480676/v1