What absorbs at 743 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 743 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 743 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

• confidence 1.0

  “RIP Fourier Transmission Infra-Red spectroscopy (FTIR) and it is found that the important peaks cm-1 cm-1 were appeared at 490 due to the benzenoid ring stretching vibration, 1562 for C cm-1 quinoid ring vibration and 743 corresponds to the”

  Antistatic and Dielectric properties of one-dimensional Al2+:Nd2O3 nanowire doped polyaniline nanocomposites for electronic application DOI: 10.1016/j.sna.2018.07.018
• N n bond confidence 1.0

  “cm(cid:2)1 cm(cid:2)1 The strong absorbance peaks at 743 and 970 can be assigned to the symmetric and asymmetric vibration modes of vibrations.23,29 n n s(P-O-P) and as(P-O-P) stretching This corresponds to the formation of PO tetrahedral c”

  High proton conductivity of NaMg1−xLixHx (PO3)3·yH2O with a three-dimensional open framework in the intermediate temperature range DOI: 10.1039/d1ma00592h
• Metal oxygen confidence 1.0

  “the same situations that the absorption band between 743 cm(cid:0) VO3(cid:0) 1 Ti-O of the BiVO4/TiO2 sample is contributed to symmetrical stretching vibrations of in monoclinic BiVO4 and the and 470 4 vibration of TiO2 [23].”

  Microstructures, thermal and electric properties of bismuth vanadium oxide (BiVO4) as an anode in electrolysis systems coated with a conductive glass indium thin oxide (ITO) DOI: 10.1016/j.csite.2021.101188
• Hydroxyl (O-H) confidence 1.0

  “Operando spectra collected in contact with ⟶h+ cm-1 218O R-FeIII-OH R-FeIV=O H+ exhibited absorption peaks at 743 and 857 (Fig.”

  Determination of photoelectrochemical water oxidation intermediates on haematite electrode surfaces using operando infrared spectroscopy DOI: 10.1038/NCHEM.2557
• Aromatic ring confidence 1.0

  “The spectra of poly (o-chloroaniline) and POC-MMT The characteristic point of phenyl C-N stretching mode appeared at nanocomposites with various load percentages 1,297cm-1, 810cm-1 743cm-1 and the spectrum values at and were (0, 1, 3, 5, 7,”

  Iqbal 等 - 2022 - Fabrication of Poly(o-Chloroaniline) to MMT Clay a DOI: 10.3389/fmats.2022.874735
• Metal oxygen confidence 1.0

  “Moreover, sharp cm-1, sharp peaks for the Zr-O group in the monoclinic zirconia are observed at 743 peaks for the Zr-O group in the monoclinic zirconia are observed at 743 cm-1, correspondcorresponding to an increase in the concentration of”

  Ponnusamy 等 - 2022 - Synthesis, Structural, and Mechanical Behavior of DOI: 10.3390/ma15082924
• Aromatic ring confidence 1.0

  “The small peaks at 1072, 1122 and 1272 were small peak at 1599 cm-1 was attributed to the aromatic ring, and C-H and C-R bending modes were cm´1 due to C-O groups, and the weak peak at 743 was attributed to aromatic =C-H bending.”

  Microcapsules Filled with a Palm Oil-Based Alkyd as Healing Agent for Epoxy Matrix DOI: 10.3390/polym8040125
• confidence 0.8

  “Downward shift to 743 cm-1 reveals uncoordinated or free TFSI anion.”

  Liew 等 - 2016 - Poly(Acrylic acid)-Based Hybrid Inorganic-Organic DOI: 10.3390/polym8050179