C=n — FTIR absorption peaks and assignments

Quick answer

C=n is usually assigned by looking for a recurring cluster of characteristic peaks rather than one exact textbook number. The table below shows where the literature most often places this group in FTIR, ranked by accumulated evidence.

Characteristic FTIR peaks for C=n

Showing the 30 best-supported peaks of 227 total for C=n.

Spectrum logic

A functional-group assignment becomes more confident when several expected bands appear together. Use this page to find the strongest-supported peaks, then confirm that the same sample exhibits a coherent pattern rather than a single isolated hit.

Real-world usage

These pages are useful for unknown material analysis, peak explanation in reports, polymer troubleshooting, and verifying whether a candidate material family is chemically plausible.

Common mistakes

• Using one functional-group page as a complete material verdict without checking the rest of the spectrum.
• Assuming the strongest band is always the most diagnostic one.
• Forgetting that processing, additives, aging, and mixtures can shift or broaden expected peaks.

Verification advice

Use DSC, GC-MS, or TGA when several material families share similar bands or when mixture effects make the FTIR assignment uncertain.

Literature behind these assignments

• 1489 cm⁻¹ confidence 1.0

  “cm-1 absorbance of the IR band at 3604 The decrease of the absorbance of the IR band at 1489 indicates a -C=N-benzene smaller weight of the ring vibrational mode after the interaction of the GO sheets with PDITC, this being in good agreemen”

  Baibarac 等 - 2019 - Adsorption of 1,4-phenylene diisothiocyanate onto DOI: 10.1038/s41598-019-48314-x
• 1519 cm⁻¹ confidence 1.0

  “The bands centered at 1519 and 1454 are assigned to C=N stretching of quinoid and C-N stretching of benzenoid rings, respectively;”

  Synthesis of novel conducting polyaniline composites based on seaweed Enteromorpha compressa macro-alga powder DOI: 10.1007/s00289-020-03191-7
• 1627 cm⁻¹ confidence 1.0

  “cm-1, For quantification, absorbance of C=O stretch cantered at 1754 between wave number of 1750 - cm-1 cm-1, 1730 was selected for Aspirin and absorbance of C=N stretch cantered at 1627 between 1690 cm-1 - 1620 was used for Omeprazole.”

  Chandarana 和 Kapupara - 2020 - Fourier Transform Infrared Spectrophotometry An E DOI: 10.30744/brjac.2179-3425.AR-25-2020
• 1605 cm⁻¹ confidence 1.0

  “LLM confirmed rule peak-group candidate”

  Synthesis, crystal structures, quantum chemical studies and corrosion inhibition potentials of 4-(((4-ethylphenyl)imino)methyl)phenol and (E)-4-((naphthalen-2-ylimino) methyl) phenol Schiff bases DOI: 10.1016/j.molstruc.2017.06.104
• 1497 cm⁻¹ confidence 1.0

  “The peaks observed at 1497, 1466 and cm-1 205 1400 are attributed to C=N stretching in aromatic compounds.”

  Effect of polyaniline (PANI) on Poly(vinylidene fluoride-co-hexaflouro propylene) (PVDF-co-HFP) polymer electrolyte membrane prepared by breath figure method DOI: 10.1016/j.polymertesting.2017.03.012
• 2270 cm⁻¹ confidence 1.0

  “Obviously, the characteristic is interesting that the viscosity of the HTPE/HDIB system cm-1 peak height at 2270 corresponding to-N=C=O”

  Curing reaction kinetics of HTPE polymer studied by simultaneous rheometry and FTIR measurements DOI: 10.1007/s10973-016-5485-8
• 1800 cm⁻¹ confidence 1.0

  “cm-1 The IR absorption bands in the region between 1800 and 1500 were mainly assigned to the C=C, C=N, and C=O stretching vibrations (Banyay et al., 2003;”

  A novel FTIR discrimination based on genomic DNA for species-specific analysis of meat and bone meal DOI: 10.1016/j.foodchem.2019.05.088
• 1602 cm⁻¹ confidence 1.0

  “cm-1 cm-1 1086 C-N stretching in amines, 1530 C=C Authors' contributions cm-1 stretching, 1602 C=N stretching (in ring),”

  Hanif 和 Zaman - 2017 - Thiolation of arabinoxylan and its application in DOI: 10.1186/s40199-017-0172-2