What absorbs at 1120 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 1120 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 fixed 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 1120 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

• Hydroxyl (O-H) confidence 1.0

  “The peak cm-1 normal at 1120 modes at the center of the Brillouin zone is given by [22] appearing is related to the vibration of hydroxyl-tin cm-1 (Sn OH) bond.”

  Azam 等 - 2012 - Effect of Mn doping on the structural and optical DOI: 10.1016/j.jallcom.2012.01.072
• Methoxy (OCH3) confidence 1.0

  “Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) spectra showed that SH-PEG mC/cm2 molecules remain attached to gold after exposure to beam doses of 1.5-60 and incubation in PBS buffer for one cm21 cm21, hour,”

  Cacao 等 - 2013 - High-Resolution, High-Throughput, Positive-Tone Pa DOI: 10.1371/journal.pone.0056835
• C c single bond confidence 1.0

  “4(a)), the clearly observable bands at positions 1120, 1390, cm-1 1605 and 1786 correspond to the C-C bend in PMDA, C-N stretch in PMDA, C=C stretch in PMDA and ODA cm-1 is due to C-H bending rings, and C=O stretch in PMDA respectively [16]”

  Chhokkar 等 - 2020 - Electrical and Structural Characterization of 100 DOI: 10.1063/5.0023335
• Nucleic acid confidence 1.0

  “Investigation by 2D correlation analysis can unrato P-O-C symmetric stretching vibrations in nucleic acids cm(cid:1)1hasbeenfound vel complex phenomena, and points to the existence of [40].The decreased absorptionat1120 an evolutionary dose”

  Melin 等 - 2004 - Sensitivity of Deinococcus radiodurans to chemical DOI: 10.1016/j.vibspec.2004.02.001
• Alkyl C-H confidence 1.0

  “consistent with C-H stretching vibrations of chemisorbed x cm-1 A small peak at 1120 may corresponds to single hydrogen of various types presents in all carbon C-N bonds arises due to N bonding to outer graphitic films.19(cid:3)20 Delivered”

  FTIR Spectroscopy of Multiwalled Carbon Nanotubes: A Simple Approachto Study the Nitrogen Doping DOI: 10.1166/jnn.2007.723
• C c single bond confidence 1.0

  “With respect to DNA, the absorption bands related to the PO symmetric stretching vibrational mode 2 cm-1) were considered, because this bond is abundant in this macromolecule in the same way that (1084 cm-1) C-N and C-C stretchings (1120 ar”

  Mostaco-Guidolin 等 - 2010 - Molecular and chemical characterization by Fourier DOI: 10.3233/SPE-2010-0466
• Acetate confidence 1.0

  “The bands at 1120, 680 and 620 represents the C-O-C of the biopolymer glycosidic linkage, the Ag-O and Cu-O bands while the SEM shows well dispersed nanoparticles with less agglomeration on the cellulosic rods.”

  Colorimetric Based Polysorbate Crosslinked Cellulose-Ag–Cu Nanohybrid Sensor for Urea Sensing Applications DOI: 10.1007/s10924-020-01703-0
• Amide confidence 1.0

  “Due to C-S vibrational mode, another peak assigned cm-1 3.3 Optical properties of CdS thin films at 1383 and C-N symmetry stretching indicated by cm-1 the bands at 1120 and C-O stretching vibration at cm-1 1001 were observed, respectively a”

  Effect of Triton X-100 surfactant on thiol-amine cosolvents assisted facile synthesized CdS thin films on glass substrate by spin coating method DOI: 10.1007/s42452-020-2423-y